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Dual_Trace Oscilloscope


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              15 MHz,TRIGGERED


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                       CORPORATION West Belle Plaine. Chicago,
    A Productof DYNASCAN        1801                         lllinois 60613

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       B & K.PRECISION

         MODEL T472C

          6460 Wesl Corflond Street
           Chicogo, lllinois 60635

                            TABLE     OF CONTENTS

INTRODUCTION                                                        4

F E A T U R E S. .



  Initial StartingProcedure                                         8
  Single{race WaveformObservation                                   8
  Calibrated VoltageMeasurement .
                                .                                  l0
  DifferentialVoltageMeasurement ..                                11
  Calibrated Time Measurement .
                              .                                    T2
  ExternalHorizontallnput (X-Y Operation) .                        13
  Z-Axis Input                                                     T4
  DualrTrace  Waveform            .
                       Observation . .                             l4

  Introduction                                                     15
  FrequencyDividerWaveforms . . .
                                .                                  15
  Divide-by-8 Circuit Waveforms . . .                              15
  Propagation  Time Measurement . .                                16
  Digital Circuit Time Relationships . .
                                    .                              16
  DistortionMeasurement                                            l8
  Gated RingingCircuit
  Delay Line Tests
  StereoAmplifi er Servicing                                       20
                                          Signals . . . . . . .
  Improvingthe Ratio of Desired-to-Undesired                       20
  Amplifier Phase  Shift Measurements                              20
  Television Servicing                                             2l

  lntroduction                                                     23
  TelevisionServicing                                              23
  SignalTracingand Peak-to-Peak  VoltageReadings                   23
  CompositeVideo WaveformAnalysis                                  23
  Sync fulse Analysis                                              25
  VITS (Vertical IntervalTest Signal)                              25
  Vectorscope Operation                                            27

  Introduction                                                     30
  Importance Sweep
             of     Alignment                                      30
  SweepAlignment Methods                                           3l
  Tuner Alignment                                                  32
  IF Alignment . .                                                 32
  ChromaAlignment                                                  33

                                 TABLE   OF CONTENTS

    FM R E C E IVE RAL IGN M EN T. .                   ......35
    P H AS EM EA SU R E M EN T                         ......35
                ME            .                        ......37
      Introduction                                            37
      T e s ti n g c e d u re                             ...38
      Analyzingthe Waveforms                              ...38
      General                                              ..42
      Vertical Preamplifiers                                  42
      Mode Logic                                           .. 42
      Vertical Amplifier                                   ..42
      TriggerCircuit                                       ..42
      SyncAmplifier and Inverter                           ..42

      Housing Removal                                        44
      230 VAC OPERATION                                      44
      Graticule Removal                                      44
      CH A and CH B DC Balance                               44
-     l12ar;rd AttenuatorBalance
               1/5                                           M
      Vertical Gain Adjustment                               44
      Horizontal Position Adiustment                         44

    WARRANTY SERVICE INSTRUCTIONS                         ...47

    WARRANTY                                              ...48



25                                                  13


     Fig. l.   Front panelcontrolsand indicators.

     l. CathodeRay Tube (CRT). This is the screenon which                   12. SOURCE switch. Three-positionlever switch selects
        the waveforms viewed.
                    are                                                         triggering source for the sweep. Both sweepsare
                                                                                triggered the same
                                                                                         by               in
                                                                                                     source dual traceoperation.
     2. S c ale.T he 8 x 1 0 c m g ra ti c u l ep ro v i d e s i brati on
          marks for voltage (vertical) and time (horizontal)                                is
                                                                                  CH A Sweep triggered Channel signal.
                                                                                                     by      A
          measurements.Illuminationof the scale fully adjust-
          able.                                                                             is
                                                                                  CH B Sweep triggered Channel signal.
                                                                                                     by      B

     3. POWERILLUM control. Fully counterclockwise                                EXT Sweepis triggered an externalsignal
                                                                                                            by          applied
          tion of this control (OFF position) turns off oscillo-                      at the E X T S Y N Cj ack 10.
          scope. Clockwise rotation turns on oscilloscope.                  1 3 . ChannelB POSITIONcontrol.Verticalpositionadjust-
          Further clockwise rotation of the controlincreases
                                                           the                                               horizontalposition
                                                                                ment for Channel trace.Becomes
          iiluminationlevelof the scale.                                        adjustmentwhen SWEEP  TIME/CM switch 5 is in the
     4. Pilot lamp. Lightswhen oscilloscope turnedon.                           CH B position.
                                                                            14. ChannelB DC BAL adjustment.
                                                                                                          Vertical DC balance
     J.   SWEEP TIME/CM switch. Horizontal coarsesweep
                                                                                adjustment Channel trace.
          time selector.Selectscalibratedsweeptimes of 0.5
          pSEC/cm(microsecond centimeter) 0.5 SEC/cm
                                 per            to                          1 5 .ChannelB INPUT Jack.Verticalinput jack of Channel
          in i 9 stepswhen VARIABLE control 6 is set to the                     B. Jack becomes external horizontal input when
          CAL position (fully clockwise).In the CH B position,                  SWEEP TIME/CM switch5 is in the CH B position.
          this switch disablesthe internal sweepgeneratorand
          permitsthe CH B input to providehorizontalsweep.                  l 6 ChannelB DC-GND-ACswitch.

     6. Sweep speed VARIABLE control. Fine sweep time                             DC    Direct input of AC and DC component input
         adjustment.[n the extreme clockwise(CAL) position                              signal.
         the sweeptime is calibrated.                                            GND Openssignalpath and grounds    input to vertical
     7 . CAL lV P-P jack. Providescalibrated I kHz, 1 volt                           amplifier.This provides zero-signal
                                                                                                             a             baseline,
         peak-to-peak squarewave input signal.This is usedfor                        the position of which can be usedas a reference
         calibrationof the vertical amplifier attenuatorsand to                      when performing measurements.
         check the frequency compensation     adjustmentof the                    AC    BlocksDC component input signal.
         probesusedwith the oscilloscope.
                                                                            t 7 . ChannelB VOLTS/CM switch.Vertical attenuatorfor
     8. <>POSITION control. Rotation adjusts horizontal                         ChannelB which providesstep adjustment vertical
        position of traces(both traceswhen operatedin the                       sensitivity.Vertical sensitivity calibrated I I steps
                                                                                                               is         in
        dual trace mode). Push-pullswitch selects5X magni-                      from .01 to 20 volts per cm when VARIABLE control
        fication when pulled out (PULL 5X MAG), normal                          18 is set to CAL position. This control adjusts
        when pushedin.                                                          horizontal sensitivity when the SWEEP TIME/CM
    9. TRJGGERINGLEVEL control. Sync level adjustment                           switch5 is in the CH B position.
       determinespoints on waveform slope where sweep                       1 8 . Channel B VARIABLE control. Vertical attenuator
       starts;(-) equalsmost negativepoint of triggeringand                       adjustment  provides fine control of verticalsensivitity.
       (+) equalsmost positive point of triggering.Push-pull                      In the extremeclockwise    (CAL) position,the vertical
       switch selectsautomatic triggering when pulled out                         attenuatoris calibrated. This control becomes fine
       (PULL AUTO). When automatic triggering,a sweepis                           horizontal gain control when the SWEEPTIME/CM
       generated  evenwithout an input signal.                                    switch5 is in the CH B position.
    10. EXT TRIG jack. Input terminals for external trigger
        signal.                                                             1 9 . MODE switch. Five-position                   the
                                                                                                           lever switch; selects
                                                                                basicoperatingmodes of the oscilloscope.
    11. SYNC switch. Four-position lever switch with the
        followingpositions:                                                      CH A     Only the input signal to Channel A is
                                                                                          displayed a single
                                                                                                  as        trace.
           SLOPE.The SLOPEpositionsare usedfor viewingall
           waveformsexcept televisioncompositevideo signals.                     CH B     Only the input signal to Channel B is
                                                                                          displayed a singletrace.
          (+) Sweep is triggered on positive-goingslope of
          waveform.                                                              A& B     Dual trace operation; both the Channel A
                                                                                          and ChannelB inpu.tsignals displayed
                                                                                                                    are        on
          (-) Sweep is triggered on negative-going
                                                 slope of                                 two separatetraces.
                                                                                 A+B      The waveforms   from ChannelA and Channel
                                                                                          B inputs are added and the sum is displayed
          TV. In the TV positions, the sync pulsesof a                                    as a singletrace.
          televisioncompositevideo signalare used to trigger
          the sweep; the vertical sync pulses (frame) are                        A- B     The waveform from ChannelB is subtracted
          automatically             for
                            selected sweep   timesof 0.5 SEC/cm                           from the Channel A waveform and the
          to 0.1 mSEC/cm,      and horizontalsyncpulses (line) are                        difference is displayed as a single trace. If
          automatically     selected sweep
                                   for      timesof 50 pSEC/cm                            only a Channel B input is present, the
          t o . 5 pS E C /c m.                                                            displayis inverted.
a         (+) Sweepis triggered positive-going
                               on            sync pulse.                    20. ChannelA VOLTS/CM switch. Vertical attenuator for
                                                                                ChannelA which providescoarse      adjustmentof vertical
          (-) Sweepis triggeredon negative-going pulse.
                                              sync                              sensitivity.Vertical sensitivityis calibratedin 11 steps
    from .01 to 20'volts per cm when VARIABLE control           26. ASTIG adjustment. Astigmatismadjustmentprovides
    21 is set to the CAL Position.                                  optimum spot roundnesswhen us9!-11--c9-njunction
                                                                    with the FOCUS control 27 and INTENSITY control
21. Channel A VARIABLE control. Vertical attenuator                 28. Very little readjustment this control is required
    adjustmentprovidesfine control of verticalsensitivity'          after initial adjustment.
    In- the extreme clockwise(CAL) position, the vertical
    attenuatoris calibrated.                                    27. FOCUScontrol.
                                                                28. INTENSITY control. Adjustsbrightness trace'
22. ChannelA DC-GNDAC switch.
                                                                29. Fuseholder.
       DC      Direct input of AC and DC component of
               input signal.                                                                 for
                                                                30. AC line cord. CSA-approved oscilloscopes.
       GND     Opens signal path and ground input to            31. INT MOD jack. Intensitymodulation(Z-axis)
               vertical amplifier. This providesa zero-signal
               baseline, the position of which can be used      32. Combinationcarryinghandleand tilt stand.
               as a reference when performingDC measure-
       AC      BlocksDC componentof input signal.                                                         ModelPR-35
                                                                33. Probe (see Fig. 3). The B & K-Precision
                                                                    combination10:l./Directprobe has been designed for
23. ChannelA INPUT jack. Vertical input jack of Channel             use with this oscilloscope. However, any probe de-
    A.                                                              signedfor use with an oscilloscopehaving a-nominal            I

      Channel A DC BAL adjustment.Vertical DC balance               in-put impedance I megohm shuntedby 27 pF and
      adjustmentfor ChannelA trace.                                 capable operation to l5 MHz, canbe used.
                                                                             of          up

25. ChannelA POSITIONcontrol. Vertical position adjust-                                                    with scale
                                                                34. Vector Overlay (not shown). Interchanges
      ment for ChannelA trace.                                                    operation.
                                                                    for vectorscope

                                           OPERATING INSTRUCTIONS
INITIAL STARTING PROCEDURE                                         The oscilloscope now ready for making waveform
 l. Set POWER ILLUM control 3 to OFF position (fully
    counterclockwise).                                                                 CAUTION
                                      50/60 FIzoutlet'
 2. Connectpower cord 30 to a 12O-volt,                             Never allow a small spot of high brilliance to
                                  25,                               remain stationary on the screenfor more than a
     control 13 and < > POSITION 8 to the centersof their           few seconds. The screenmay becomepermanently
    .ranges.                                                        burned. Reduce intensity or keep the spot in
                                                                    motion by causing to sweeP.
 4. Pull TRIGGERING LEVEL control 9 to the AUTO
 5. Set CH A DC'GND-AC switch 22 and CH B
    DC-GND-ACswitch 16 to the GND positions.
                                                                 SINGLE.TRACE WAVEFORM OBSERVATION
 6. Set the MODE switch 19 to the CH B position for
    single -trace operation or the A & B position for               Either Channel A or Channel B can be used for
    dual-trace  operation.                                                  operation.The advantage using ChannelB is
                                                                 single-trace                        of
                                                                 that the polahty of the observed waveformcan be reversed
 7. Turn on oscilloscope rotating the POWER ILLUM
                             by                                  by placingthe MODE switch 19 in the A-B positionif there
    control 3 clockwise. will "click" on and pilot lamp 4
                          It                                     ii no input to Channel A. For convenience, ChannelB is
    will light. Turn control clockwiseto the desiredscale2       usedin the following instructions.
                                                                  1. Perform the steps of the "Initial StartingProcedute"
 8. Wait a few seconds the cathoderay tube (CRT) to
                         for                                         with the MODE-switch 19 in the CH B position.Then
    warm up. A trace (two tracesif operatingin the A & B             connect the probe cableto the CH B INPUT jack 15.
    mode) shouldappearon the face of the CRT.                        The following instructions assume the use of the
                                                                     B & K-Precision Model PR-35combinationprobes.
  9. I f no trace appears, increase (clockwise) the
                                                                  2. For all except low-amplitude waveforms,the probes
     INTENSITY control 28 settinguntil the traceis easily
                                                                     arc set for l0:l attentuation. For low-amplitude
                                                                     waveforms(below 0.5 volt peak-to-peak), the probe
 10. Adjust FOCUS control 27 and INTENSITY control 28                for DIRect. See Fig. 3 for changingthe probesfrom
     for the thinnest,sharPest                                       10:l to DIRect, or vice versa.The probe has a 10
             positioncontrols8, 25 and l3 if necessary,              megohm input impedance with only l8pl shunt
 11. Readjust
     centerthe traces.                                               capacitance the 10:l position and I megohmwith
                                                                     tiO pf shunt capacitance the DIRect position.The
 12. Checkfor proper adjustmentof ASTIG control 26, and
               -controls                                             hightir input imp-edance(low'capacity position) should
     DC BAL              14 and 24 as describedin the                be usedwhen possible, decrease
                                                                                           to          circuit loading.       Y
     manual. These adjustments require checking only              3. Set CH B DC-GNDAC switch 16 to AC for measuring
                                                                     only the AC component (this is the normal position for

                       COMBINATION     FEET
                        A N D C O R DW R A P

                         Fig. 2.   Rear and side panel facilities.

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                             \                                   PRoBE coMPENSATIoN
                            1O:1                                    ADJUSTMENT

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                                    3 .P U s H A c K o c E r H E R
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                                    Fig.3.    Probedetails.

     most mdasurements   and must be used if the point                         porti on i s di spl ayed. s i s becausehe
                                                                  as a smal l er                       Thi           t
     being measured includesa large DC component).Use             sweepspeedincreases       but the sweep repetitionrate
     the DC positionfor measuringboth the AC component            does not change.
     and the DC reference,and any time a very low
     frequencywaveform(below 5 Hz) is to be observed.                                   NOTE
     The GND positionis requiredonly when a zero-signal           Whenusingvery fast sweepspeed low repe.tition
     ground reference required,such as for DC voltage
                      is                                          rates,the operatormay wish to operatewith the
     readings.                                                    intensity control toward maximum. Under these
                                                                  conditions,a retrace "pip" may appear at the
4. Connectgound clip of probe to chassis groundof the             extremeleft of the trace.This doesnot in any way
   equipmentunder test. Connectthe tip of the probeto             affect the oscilloscope  operation and may be
   the point in the circuit where the waveform is to be           di sregarded.
                                                              10. After obtaining the desirednumberof waveforms, in
                        WARNING                                   step f. it is sometimesdesirableto make a final
                                                                  adjustrnent the TRIGGERING LEVEL control 9.
     a.   If the equipment under test is a trans-                 The (-) direction selects the most negative point on
          formerless powereditem, use an isolation
                   AC                                             the waveformat which sweeptriggering  will occur and
          transformer to prevent dangerouselectrical              the (+.1directionselects most positive
                                                                                          the              point on the
          shock.                                                  waveform at which sweep triiggering  will occur. The
                                                                  control may be adjustedto start the sweepon any
                                                                  desiredportion of the waveform.
     b.   The peak-to-peakvoltage at the point of
          measurementshould not exceed 600 volts
          when usingthe DIRect position of the probe.         i l. For a close-up view of a portion of the waveform, pull
                                                                   outward on the < > POSITIONcontrol 8. This expands
                                                                   the sweepby a factor of five (5X magnification)   and
5. Set CH B VOLTS/CM switch 17 and the VARIABLE                    displaysonly the centerportion of the sweep. view
   control 18 to a positionthat gives2to 6 cm (two to              a portion ro the left of center,turn the < > POSITION
   six large squareson the scale)vertical deflection.The
                                                                   control clockwise. and to view portionsto the right of
   display on the screenwill probably be unsynchronized.           c€nter.turn the control counterclockwise. inward
   The lemaining steps are concerned with adjusting                on the control to return the sweepto the normal,
   synchronization and sweep speed, which presentsa                non-        ed
                                                                       magnifi condition.
   stable display showing the desired number of wave-
   forms. Any signal that producesat least I cm vertical
                                                              CALIBRATED VOLTAGE MEASUREMENT(SeeFig. a)
   deflection develops sufficient tigger signal to syn-
   chronize the sweep.                                                       peak-to-peak
                                                                Peak voltages.                    DC voltages
                                                                                          voltages,          and
                                                              voltages a specificportion of a complexwaveformare
6. Set SOURCE switch 12 to the CH B position. This            easily and accurately measuredon the Model 1472C
   providesinternal sync so that the ChannelB waveform                ope.
   being observed alsousedto triggerthe sweep.  During         1. Adjust controlsas previously
                                                                                             instructedto displaythe
   single trace operation on Channel A, the SOURCE                         to
                                                                  w aveform be measured.
   switch should be placed in the CH A position for
   internal sync. Most waveformsshouldbe viewedusing           2. Be surethe CH B verticalVARIABLE control 18 is set
   internal sync.Whenan externalsync sourceis required,           fully clockwise the CAL position.
   the SOURCE switch should be placed in the EXT               3. Set CH B VOLTSiCM switch 17 for the maximum
   position and a cable should be connected from the              vertical deflection possible without exceedingthe
   EXT TRIG jack l0 to the externalsyncsource.                    limits of the verticalscale.
7. Set SYNC switch 1l to the TV(+) or TV(-) positions          4. Read the amount of vertical deflection (in cm) from
   for observing televisioncompositevideo waveformsor             the scale.The CH B POSITION control 13 may be
   to the SLOPE(+)or SLOPE(-) positionsfor observing              readjustedto shift the reference point for easierscale
   all other types of waveforms.Use the (+) position if           readingif desired.Whenmeasuring DC voltage,adjust
   the sweepis to be triggered a positive-going
                              by               wave,or            the CH B POSITION control 13 to a convenient
   the (-) position if the sweepis to be triggeredby a            reference with the CH B DC-GND-AC     switch l6 in the
   negative-goingwave. If the type of waveform is                 GND position, then note the amount the trace is
   unknown, the SLOPE(+)position may be used.                     deflectedwhen the switch is placedin the DC position.
8. ReadjustTRIGGERING LEVEL control 9 to obtain a                 The trace deflectsupward for a positivevoltageinput
                                                                  and downwardfor a negative  voltageinput.
   synchronized  displaywithout jitter. As a startingpoint,
   the control may be pushedin and rotated to any point                                 NOTE
   that will producea sweep,which is usuallysomewhere            For an accuratedisplay of high-frequency       wave-
   in the center portion of its range. The trace will            forms abovel0 MHz, it is important that (1) the
   disappearif there is inadequatesignal to trigger the          probe be used in the 10:1 position to reduce
   sweep,such as when measuringDC or extremelylow                circuit loading;(2) the oscilloscope controlsbe set
   amplitude waveforms.If no sweep can be obtained,              so that the height of the pattern doesnot exceed  4
   pull the control out (PULL AUTO) for automatic                cm;and (3) the tracebe centered    vertically.
                                                               5. Calculatethe voltage readingas follows: Multiply the
9. Set SWEEP TIME/CM switch 5 and VARIABLE                        vertical deflection (in cm) by the VOLTS/CM control       b
   control 6 for the desirednumber of whveforms. These            l7 setting(seeexamplein Fig. a). Don't forget that the
   controls may be set for viewing only a portion of a            voltage reading displayedon the oscilloscope only
   waveform,but the tracebecomes  progressivelydimmer             l/10th the actual voltage being measuredwhen the

       probe is set for 10:I ittenuation. The actualvoltageis                       3 . Connect ground clips of the two probesto the chassis
       displayed when the probe is set for DlRect measure'                               of equipment under test, and connect tips of the
       ment.                                                                             probesto the pointsin the circuit wheremeasurements
                                                                                         are to be made. It is usuallydesirable connectthe
    6. Calibration accuracy of this oscilloscope   may be
                                                                                         CH A probe to the higherpotential or higheramplitude
       occasionallycheckedby observing  the I volt peak-to-                              point in the circuit and the CH B probe to the lower
       peak squarewave signai availableat the CAL 1V P-P                                 potentialor lower amplitudepoint in the circuit.
       jack 7. This calibratedsourceshould read exactly I
       volt peak-to-peak. a need for recalibration in-
                          If                         is                             A
                                                                                    +.   Set the MODE switch 19 to the CH A positionand the
       dicated, see the "MAINTENANCE AND CALIBRA-                                        SOURCEswitch 12 to the CH A positionand adjust
       TION" sectionof the manualfor complete  procedures.                               the controls as previouslyinstructedin the "Single-
                                                                                         Trace WaveformObservation"    procedureto obtain a
                                                                                         synchronizedsingle waveform of 2 to 6 cm vertical
    DIFFERENTIAL VOLTAGE MEASUREMENT(SeeFig. 5)                                          heightwith the cH A VARIABLE control2l setto cAL.
       This oscilloscope may be usedto observe   waveforms and                      5 . If only the AC component of the waveform is of
    measure  voltages  between two pointsin a circuit,neitherof                          interest, the followingprocedure:
    which is circuit ground.Suchmeasurements the inputs to
    a differential amplifier, the output of a phasesplitter or                           a.                                      22
                                                                                               Set CH A and CH B DC-GND-ACswitches and
    push-pullamplifier,the amount of signaldeveloped    acrossa                                16 both to the AC position.
    single section of voltage divider or attenuator, and many                            b.    Set CH B VARIABLE control 18 to CAL and the
    others,requirethis technique.                                                              CH B VOLTS/CM switch 17 to the sameposition
                                                                                               asthe CH A VOLTS/CMswitch20.
     1. Adjust controls as previously describedunder "Initial
        StartingProcedure."                                                              c.    If the Channel A and Channel B inputs are in
                                                                                               phase, set the MODE switch l9 to the A-B
    2. Connecta probe cable to both the CH A and CH B                                          position. The displayedwaveform is the peak'to-
       INPUTjacks23 and 15.                                                                    peak differencebetween the two points of meas-

                                     a>    P O S I T I O NC O N T R O L A D J U S T E D S O T H A T
                                           TOP OF WAVEFORM CROSSES ENTEROF           C
                                           VERTICALSCALEMARKER FOR ACCURACY
                                           A N D E A S EO F R E A D I N G


                                                                                                              o ['l@
              P O S I T I O NC O N T R O L A D J U S T ED
              SO THAT BOTTOMOF WAVE-
              A H O R I Z O N T A LR E F E R E N C E I N E
                                                                            pc?@fl                                             CHB

                                                                                              VOLTS/cm            CAL
                                                                                               SET TO

                           V E R T I C A L D E FL E C T I O N = 4 . 2 c m                                10:1
                                          VOLTAGE/CM =            .o2                         P R O B EA T T E N U A T I O N
                              P R O B EA T T E N U A T I O N = 1 0
                       P E A K . T O . P E A KW A V E F O R M = 0 . 8 4 V


                                                        Fig. 4.      Typical voltagemeasurement.

            urement. If the waveform is small, the vertical          6. If a DC voltage,or the DC componentof the waveform
            sensitivitymay be increased
                                      but the CH A and CH               is of interest,usethe following procedure:
            B VOLTS/CM switchesmust both be in the same
            position.                                                   a.   Set CH A DC-GND-AC switch 22 to the DC
      d.    If the Channel A and ChannelB inputs are 180"
                                                                        b.   Position the CH A VOLTS/CM switch 20 to keep
            out of phase, such as the output of a push-pull
                                                                             the trace within the limits of the vertical scale.
            amplifier, set the MODE switch 19 to the A-B
                                                                             Use the CH A POSITION control 25 to align the
            position to measurethe full peak-to-peak  wave-                  trace with one of the lines on the scale for
            form. Set the MODE switch to the A+B position
            to measure  any imbalancebetweenthe two points
            of measurement. Readjust the VOLTS/CM                       c.   Position CH B VOLTS/CM switch 17 to the same
            switches and 20 as required obtainaslargea
                     l7                   to                                 position as the CH A VOLTS/CM switch.
            waveformas possible  without exceeding limits
                                                  the                   d.   Set CH B DC-GNDAC switch 16 to the GND
            of the verticalscale, alwayskeepthe CH A and
                                but                                          position and adjust out any error that may be
            CH B switches to the samesensitivity.                            introducedby the ChannelB positioning     control
      e.    Position the waveform as desired with the                        as follows: Alternatelyset the MODE switch l9 to
            positioningcontrolsand calculate peak-to-peak
                                           the                               the A+B and A-B positions,adjustingthe CH B
            voltage as described the "CalibratedVoltage
                                in                                           POSITIONcontrol l3 until the tracepositiondoes
            Measurement"  procedure.                                         not shift as the MODE switch position changes.
                                                                        e.   Return CH B DC-GNDAC switch 16 to the DC                 {
                                                                             posi ti on.
                                                                        f.   Momentarilyreturn the MODE switch 19 to the               1

                                                   0                         CH A position and note the trace position for
                                                        @)..t                reference. You may readjustit with the ChannelA          il

                                                           ['-l t
                                                                             verticalpositioningcontrol,but not the Channel
                                                   a                         control. Place the MODE switch in the A-B
                                                                                                                           B          i

                                                                             position. The amount of displacement the trace
                                                           L--=lg            from the Channel A reference representsthe
                                                                             voltage differential between the two points of

                                                                    CALIBRATED TIME MEASUREMENT (SeeFig. 6)
                                                                       Pulse width, waveform periods, circuit delays and all
                                                                    other waveform time durations are easily and accurately
                                                                    measuredon this oscilloscope.  Calibrated time measure-
                                                                    ments from .5 second down to 0.1 microsecondare
                                                                    possible.At low sweepspeeds, entire waveformis not
                                                                    visible at one time. However,the bright spot can be seen
                                                                    moving from left to right acrossthe screen, which makes
                                                                    the beginningand ending points of the measurement   easy
                                                                    to spot.
                                                                     1. Adjust controls as previously describedfor a stable
                                                                        displayof the desiredwavefbrm.
                                                                     2. Be sure the sweeptime VARIABLE control 6 is fully
                                                                        clockwiseto the CAL position.
     PUSH-PULL                                                       3. Set the SWEEPTIME/CM control 5 for the largest
     A M P L IF I E R                                                   possible display of the waveform segment to be
                                                                        measured, usuallyone cycle.
                                                                     4. If necessary,  readjustthe TRIGGERING LEVEL con-
                                                                        trol 9 for the most stabledisplay.

                                                                     5. Read the amount of horizontal deflection (in cm)
                                                                        be tween the points of measurement. The < >
                                EXAMPLE:                                POSITIONcontrol 8 may be readjusted alignone of
                                                                                      points with a verticalscale
                                                                        the measurement                          marker for
                   VERTICAL DEFLECTION = 6cm
                            VOLTAGE/cm = .O2
                                                                     6. Calculatethe time duration as follows: Multiply the
                                                                        horizontal deflection (in cm) by the SWEEP  TIME/CM
                        PROBE ATTENUATION 1 0
                                                                        switch 5 setting(see examplein Fig. 5). Remember,
              P E A K . T O - P E A KW A V E F O R M 12V                when the 5X magnification is used, the result must
                                                                        be dividedby 5 to obtain the actual time duration.
                                                                     7. Time measdrements often requireexternalsync.This is
            Fig. 5.      Typical differentialmeasurement.               especiallytrue when measuringdelays. The sweep is
                                                                        started by a sync signal from one circuit and the

                                                                      H O RI Z O N T A L
                                                                      D EF L E C T IO N
          P O S I T I O NC O N T R O L A D J U S T E DS O                                                                            VARIABLE
          T H A T L E A D I N G E D G EO F W A V E .                                                 @                               SCtOCAL
          F O R M A L I G N SW I T H A V E R T I C A L                                                                               SWEEP IME/CMT
          R E F E R E N C E I N E .E D G E
          M A Y N O T B E V I S I B L EO N V E R Y
                                                                                                     o                               s e t t o 10 ! r s e c

          ALIGNWHEREVER AVEFORM     W                                                                @                               , t o O P s e tt o Q
                                                                                                                                     ( S Ls t a rEs w e e po n
          B E GI N S .                                                                                                                           t
                                                                                                                                     negative-going ge)    ed

          P O S I T I O NC O N T R O L A D J U S T E D S O
          T H A T T R A I L I N G E D G EO F W A V E F O R M
          C R O S S E S O R I Z O N T A LS C A L E M A R K E R
          F O R A C C U R A C YA N D E A S E O F R E A D I N G


          H O R I Z O N T A L D E F L E C T I O N= 6 . 3 5 c m
                          SWEEP IME/CM- 1OpSEC
                         TIME DURATION - 63.5uSEC
          ( o rP E R I O D ) F W A V E F O R M

                   FREOUENCY=            1 =             1
                                       TtN/iE ^0000635€EC                                                            S
                                                                                                      D I S P L A Y S H O WT Y P I C A L T E L E V ! S I O N
                                                                                                      R E C E I V E R A V E F O R MA T G R I D O F
                                             = 1 5 , 1 5 OH z                                         H O R I Z O N T A L O U T P U TT U B E

                                                            Fig. 6.     Typicaltime measurement.

    waveformmeasured a subsequent
                      in              circuit. This allows                                 phase measurement,or an external sweep voltage. This
    measurement the display between the sync pulse                                         input must be 10 mV per cm of deflection greater;
                                                                                                                                   or        thus
    and the subsequentwaveform.To perform such meas-                                       any voltage of 100 mV or greater is sufficient for
    urementsusing external sync, use the following steps:                                  satisfactoryoperation. use an external
                                                                                                                To               horizontalinput,
    a.   set the souRCE switch 12 to the EXT position.                                     usethe followingprocedure:

    b.   Connecta cable from the EXT TRIG iack 10 to                                        t . Set the SWEEPTIME/CM switch 5 fullv clockwiseto
         the source of sync signal. Use a shori shielded                                       the C H B posi ti on.
                                                                                            2. Use the ChannelA probe for the verticalinput and the
    c.   Set the SYNC switch 1l to the SLOpE (+) or (-)                                       ChannelB probe for the horizontal input.
         position for the proper polarity for the sync signal.
                                                                                            3. Adjust the amount of horizontal deflection with the
    d.   Readjustthe TRIGGERING LEVEL control 9 if                                             CH B VOLTS/CMand VARIABLE controls17 and 18.
         necessary a stablewaveform.
                                                                                            4. The CH B (vertical)POSITIONcontrol now serves
    e.   If measuringa delay, measurethe time from the                                         as the horizontalpositioncontrol, and the <> POSI-
         start of the sweepto the start of the waveform.
                                                                                               TION control is disabled.
 8. Another excellentmethod for measuringtime delaysis
    with dual-traceoperation.The procedures given in
                                           are                                                                             NOTE
    the "DUAL-TRACE APPLICATIONS" section of the
    manual.                                                                                      Do NOT usethe PULL 5X MAG conrrol durins
                                                                                               X-Y operation.Use the CH B VARIABLE and
EXTERNAL HORTZONTAL rNpUT (X-y OPERATTON)                                                      VOLTS/CMcontrolsto adjusthorizontalgain.
   For some measurements, externalhorizontal deflec-
tion signalis required. This is also referred to as an X-y                                 5. All sync controls are disconnected
                                                                                                                               and have no effect.
measurement,where the Y input provides vertical de-
flection and the X rnput provideshorizontaldeflection.The
horizontal input may be a sinusoidalwave, such as for

                                                             6. Set both the CH A and CH B DC-GNDAC switches       22
                                                                and l6 to the AC position.This is the positionusedfor
                                                                most measurements   and must be used if the points
                                                                beingmeasured  includea largeDC component.

                                                              7. Connect the ground clips of the probesto the chassis
                                                                 ground of the equipmentunder test. Connectthe tips
                                                                 of the probes to points in the circuit where the
                                                                 waveformsare to be measured. is preferredthat the
                                                                 signalto which the waveformwill be synchronized be
                                                                 appliedto the ChannelA input.
                                                                 a.   If the equipmentunder test is a transformer-
                                                                      less AC unit, use an isolation transformerto
                                                                      preventdangerous   electricalshock.
                                                                 b.   The peak-to-peakvoltage at the point of
                                                                      measurement   should not exceed600 volts, if
                                                                      the probe is usedin the DIR position.
      Fig. 7.              trace with Z-axisinput.
                Oscilloscope                                  8. Set the VOLTS/CM controlsl7 and 20 for Channels  A
                                                                 and B to a position that gives 2 to 3 cm vertical
                                                                           The displays the screen
                                                                 deflection.            on          will probablybe
ZA)flS IMUT                                                      unsynchronized. The remainingsteps,although similar
   The trace displayed on the screen may be intensity            to those outlined for single-trace
modulated (Z-axis input) where frequency or time-scale           the procedure for obtaining stable, synchronized
marks are required.A 2O-voltpeak-to-peak greatersignal
                                        or                       displays.
appliedat the INT MOD (intensitymodulation) jack 3l on        9. Set the SOURCEswitch 12 to the CH A position.This
the rear of the oscilloscope providealternate
                           will              brightness          provides internalsync so that the Channel waveform
and blankingof the trace.SeeFig. 7.                              being observedis also used to trigger the sweep.If
                                                                 desired, the Channel B waveform may be used to
DUAL{RACE WAVEFORM OBSERVATION                                                    by
                                                                 triggerthe sweep settingthe SOURCEswitch to the
(Refer to Fig. 8 )                                               CH B position. Often in dual-trace operation,a sync
                                                                 sourceother than the measurement    point for Channel
   In observing simultanedus             on
                              waveforms channels andA
                                                                 A or B is required.In this case ttre SOURCEswitch
B, it is necessarythat the waveforms be related in
frequencyor that one of the waveforms synchronized
the other althoughthe basicfrequencies
                                       by              to
                                         may be different.
                                                                 to the EXT (external) position and connect a cable
                                                                 from the EXT TRIG jack l0 to the sync source.               a
An example of this is in checkinga frequency divider or      1 0 . Set the SYNC switch 1l to the TV(+) or TV(-)
multiplier.The reference, "clock" frequency
                         or                   canbe used         positions for observing television composite video
on Channel A, for example, and the multiple or sub-              waveforms, or to the SLOPE (+) or SLOPE (-)
multiple of this referenie frequency will be displayedon         positionsfor observingall other types of waveforms.
Channel B. In this Way, when the waveform display of             Use the (+) positionsif the sweepis to be triggeredby
ChannelA is synchronized,    the display on ChannelB will        a positive-goingwave, or to the (-) position if the
also be in qync with the Channel A display. If two                     is
                                                                 sweep to be triggered a negative-going
                                                                                        by                 wave.
waveformshaving no phase or frequency relationshipto
each other are displayedsimultaneously, will be difficult
                                         it                  1 1 . Adjust TRIGGERING LEVEL control 9 to obtain a
if not impossibleto lock both waveformsin sync for any             stable, synchronizedsweep. As a starting point, the
usefulobservation.                                                 control may be pushedin and rotated to any point that
                                                                   will produce a sweep,which is usually somewhere     in
                                        for observa-
   To display two waveformssimultaneously                          the center portion of its range.The tracewill disappear
tion, usethe following procedure:                                  if there is inadequate signalto trigger the sweep,such
 l. Perform the stepsof the "Initial StartingProcedure."           as when measuring  extremely low amplitudesignals.  If
                                                                   no sweepcan be obtained,pull out the control (PULL
                       probe cablesto both the CH A
 2. Connect oscilloscope                                           AUTO) for automatictriggering.
    and CH B INPUTjacks23 and 15.
                                                             t 2 . Set SWEEP TIME/CM switch 5 and VARIABLE
3. If the recommendedB & K-PrecisionModel PR-35                  control 6 for the desirednumber of waveforms.   These
    oscilloscopeprobesare used, 10:1 attenuation should          controls may be set for viewingonly a portion of a
   be used except for waveformsof 0.5 volt peak-to-peak          waveform,  but the tracebecomes   progressively
   or less.For the lower amplitudewaveforms DIP.ect              asa smaller portion is displayed.
   position should be used. See Fig. 3 for changingthe
   probe from 10:1 to DIR or vice versa.Whenever             13. After obtainingthe desirednumber of waveforms in
   possible, use the high impedance,   low capacity 10:1         step 12, it is sometimesdesirable to make a final
   position to minimize circuit loading.                         adjustment of the TRIGGERING LEVEL control 9.
                                                                 The (-) direction of rotation selects most negative
 4. Set MODE switch 19 to the A & B position.Two traces          point on the sync waveformat which sweep  triggering
    shouldappearon the screen.                                   will occur and the (+) direction selectsthe most
 5. Adjust CH A and CH B POSITIONcontrols25 and 13               positive point on the sync waveform at which sweep          3
    to place the Channel A trace above the Channel B             triggeringwill occur. The control may be adjustedto
    trace.and adiustboth tracesto a convenient                   start the sweep on any desired portion of the sync
    mark on the icale.                                           waveform.

        14. The observedwaveformsof Channels and B can be
                                               A                                    FREQUENCYDIVIDER WAVEFORMS
            expanded by a factor of 5 by pulling outward on                            Fig. 8 illustratesthe waveformsinvolved in a basic
            the <> POSITION control 8. This control can then be                     divide-by-twocircuit. Fig. A indicates the referenceor
            rotated clockwiseor counterclockwise view the left
                                               to                                   "clock" pulsetrain. Fig. B and Fig. C indicatethe possible
            and right extremes of the waveform displays as                          outputsof the divide-by-two  circuitry. Fig. 8 alsoindicates
            desued. Push inward on the control to return the                        the settingsof specificoscilloscope   controls for viewing
            sweepto the normal, non-magnifiedcondition.                             thesewaveforms. additionto these
                                                                                                     In                  basiccontrol settings,
        15. Calibrated voltagemeasurements,  calibrated  time meas-                 the TRIGGERING LEVEL control, as well as the Channel
            urementsand operation with Z-axisinput are identical                    A and ChannelB verticalpositioncontrolsshouldbe setas
            to thosepreviouslydescribed single-trace
                                        for               operation.                required producesuitabie
                                                                                            to                  displays. the drawingof Fig.
            Either the ChannelA or ChannelB verticaladjustment                      8, the waveformlevelsof 2 cm are indicated. the exact
            controls can be used as required in conjunction with                    voltage amplitudes of the Channel A and Channel B
            the horizontal sweepcontrols to obtain the required                     waveforms are desired,the Channel A and Channel B
            amplitude or time interval measurements.   This can be                  VARIABLE controls must be placedin the CAL position.
            done either by using the dual display facilitiessuch as                 The ChannelB waveformmay be either that indicatedin
           the A & B position of the MODE switch or by reverting                    Fig. 88 or 8C. In Fig. 8C the divide-by-twooutput
           to single-trace operation, using the CH A or CH B                        waveformis shown for the casewherethe output circuitry
           positionsof the MODE switch.                                             responds a negative-going
                                                                                              to                  waveform.ln this case,the
                                                                                    output waveformis shiftedwith respect the leading
                                                                                                                             to            edge
        16. The ChannelA and ChannelB waveformdisplayscan                           of the reference frequency pulse by a time interval
            be added algebraicallyby placing the MODE switch in                                   to
                                                                                    corresponding the pulsewidth.
            the tr+B position, or subtracted algebraicallyin the
            A-B position.                                                          DIVIDF-BY-8 CIRCUIT WAVEFORMS
                                                                                      Fig. 9 indicates waveform relationshipsfor a basic
{                                                                                  divide-by-eight
                                                                                                 circuit. The basic oscilloscopesettingsare
                   DUAI-TRACE APPLICATIONS                                                  to
                                                                                   identical thoseusedin Fig. 8. The referencefrequency  of
                                                                                   Fig. 94 is supplied to the Channel A input, and the
        INTRODUCTION                                                               divide-by-eight
                                                                                                 output is applied to the ChannelB input.
           The most obviousand yet the most useful featureof the                   Fig. B indicatesthe ideal time relationshipbetweenthe
        dual- trace oscilloscopeis that it has the capability for                  input pulsesand the output pulse.
        viewing simultaneouslytwo waveforms       that are frequency-                 In an applicationwherethe logiccircuitryis operating  at
        or phase-related, that have a common synchronizing
                           or                                                      or near its maximum designfrequency,the accumulated
        voltage, suchasin digitalcircuitry.Simultaneous    viewingof               risetime effectsof the consecutive stagesproducea built-in
        "Causeand Effect" waveforms an invaluable to the
                                          is                aid                    time propagationdelay which can be significantin a critical
        circuit designer the repairman.
                         or                  Severalpossible  applica-             circuit and must be compensated Fig. 9C indicates
                                                                                                                    for.                  the
        tions of the dual-trace oscilloscope    will be reviewedin                 possible time delay which may be introduced into a
        detail to familiarizethe user further in the basicooeration                frequency divider circuit. By use of the dual trace oscillo-
        of this oscilloscope.                                                            the
                                                                                   scope input and output waveforms be superimposed

                                                           fi,itt|3hfr                                   t
             A . ^ R E F E R N C E F R E O U E N C YP U L S ET R A I N
                  ( 1 O O O U L S E S E RS E C O N D )
                          P          P

                         LEADING EDGES MAY NOT BE
                         VISIBLE AT FAST SWEEP RATES

              c H n ,/r-
             B . D I V I D E - B Y - T W O O U T P U TS Y N C H R O N I Z E D O
                 L E A D I N G E D G EO F R E F E R E N C E U L S E
                                                            P                        WAVEFORM      WAVEFORM
                                                                                          A             B
                - l*ro                                                                 HEIGHT        H E IG H T
             C . D I V I D E - B Y . T W O O U T P U TS Y N C H R O N I Z E D O
                 T R A I L I N G E D G EO F R E F E R E N C E U L S E
                                                         Fig. 8.     Waveforms divide-by-two
                                                                             in             circuit.

                                                                                    zontally. This may be done by pulling the PULL 5X MAG
                                                                                    control. It alsomay be possible view the desired
                                                                                                                   to               portion
                                                                                    of the waveformat a fastersweepspeed.

                                                                                                     TIME RELATIONSHIPS
                                                                                     DIGITAL CIRCI.JIT
                                                                                       A dual-trace oscilloscopeis a necessityin designing,
                                                                                     manufacturing servicing
                                                                                                  and                          A
                                                                                                              digitalequipment. dual-trace
                                                                                                permitseasycomparison time relationships
                                                                                     oscilloscope                      of
                                                                                     between two waveforms.
       fig. g.                in divide-by-eight
                                               circuit.                                 ln digitalequipmentit is commonfor a largenumberof
                                                                                     circuits to be synchronized, to have a specifictime
to determine the exact amount of propagationdelay that                               relationship to each other. Many of the circuits are
occurs.                                                                              frequencydividersas previously               but
                                                                                                                       described, waveforms
                                                                                     are often time-related many other combinations. the
                                                                                                             in                            In
PROPAGATIONTIME MEASUREMENT                                                          dynamic state, some of the waveforms      change, depending
    An example of propagationdelay in a divide-by-eight                              upon the i nput or mode of operati on.Fi g. 1 1 showsa
circuit was given in the previousparagraph.              Significant                 typical digitalcircuit and identifiesseveral the pointsat
propagationdelay may occur in any circuit with several                               which waveform measurements          are appropriate. The
consecutive    stages.  This oscilloscope     has featureswhich                      accompanying    Fig. l2 showsthe normal waveforms be   to
simplify measurement propagation
                         of                  delay. Fig. 10 shows                    expectedat eachof thesepoints and their timing relation-
the resultantwaveforms      when the dual-trace      presentation  is                ships.The individualwaveforms      have limited valueunless
combinedinto a single-trace          presentation selecting
                                                   by            the                 their timing relationshipto one or more of the other
A+B or A-B position of the MODE switch. In the A+B                                   waveforms known to be correct.The dual-trace
                                                                                                 is                                      oscillo-
position the two inputs are algebraically        addedin a single                    scope allows this comparison to be made. In typical
trace display.Similarly,in the A-B positionthe two inputs                            fashion,wavefornr                              on
                                                                                                         No. 3 would be displayed Channel      A
are algebraicallysubtracted.Either position provides ^                               and w aveformN o. 4 thru N o. 8, and N o. 10, would be
precisedisplay of the propagationtime (Tp). Using the                                successively            on          B,
                                                                                                  displayed Channel although         other timing
procedures   given for calibrated      time measure^m€nt, carTp                      comparisons    may be desired. Waveforms    No. 11 through
b e c alc ulat ed. m o rep re c i s e a s u re m e n a nb e obthi ned
                A                   me             ct                                No. 13 would probably be displayedon ChannelB in
if the Tp portion of the waveform is expandedhori-                                   rel ati onshito w aveform o. 8 or N o. 4 on C hannel
                                                                                                  o             N                        A.


                                                                       Il*to                                                                     \

                                                                             I L                     I
                                                                                                     1                                                   I
                                                                                                 I                    \--
                                                                  \- - r -
                                                                              -t'                                /\                  \
                                                                       I                                                                     \
                                EXPAND THrS PORTTON /
                                F O R M O R E P R E C T S E- (
                                T|ME MEASUREMENT                             _ _
                                                               \_                _.                                                                      \
                                                              /        +l t+Tp \
                                                                         ll      \l
                                                                                                     I                                                       I
            A-B                                                                               I
                                                                                             I                                                       /
                                                                                         /                                               /
                                                                       \-       ./                                                                               rb.

                               Fig. 10. UsingA+B or A-B m-odes propagation
                                                             for         time measurement.

   In the family of time-related      waveformsshownin Fig.                   sourcebecause   they do not contain a triggeringpulseat the
ll. wav ef or m o .8 o r N o . l 0 i s a n e x c e l l ent
               N                                         syncsource           start of the frame. [t would not be necessary view the
ior viewingall of the waveforms;      thereis but one triggering              entire waveforms shown in Fig. 12 in all cases. fact,
                                                                                                as                                In
pulse per frame. For convenience,           external sync using               there are many times when a closer examination of a
wav ef or mNo.8 o r N o . 1 0 a s th e s y n c s o urcemay be                 portion of the waveforms    would be appropriate. such
desirable.With externalsync,any of the waveforms            may be                   it
                                                                              cases, is recommended     that the syncremainunchanged
displayed without readjustmentof the sync controls.                           while the sweepspeedor 5X magnificationbe used to
Waveforms  No. 4 thru No. 7 shouldnot be usedasthe svnc                       expandthe waveformdisplay.

                                                          8tT I

                                                        S E C UR I T Y

                                                           BIT 2

                                                                                                       LINE DRIVER
                                                                                                             -    -     --15
          DATA                                                                                                   ui48    |
         INPUT                                              u.2                                                   N16
      (8-8rrS)                                            M U L T I-


                                                                                                             4 5 6 7 8
                                                        S E C U R IT Y
                                                                               OATA ENABLE
                                                           BIT 3

                                                                         II     OATA SELECI   LINE_O   (8)
                                                                                            rNE- C (4)
                                                                                 TA SELECT LINE_A (I )

                                                                                                                                   UtO,-:   l6
                                                                                                                                   C O U N T ER


                         €No   FRAME RESET    Y     4

                                Fig. I l. Typical digital circuit using several

   An amplifier stage,or an entire amplifier unit, rnay be                                                      4. SetMODE switchto A & B.
tested for distortion with this oscilloscope.This type of                                                       5 . Set sync SLOPEswitch to CH A and adjustcontrolsas
measurementis especiallyvaluable when the slope of a                                                                describedin waveform viewing procedure.  for syn-
waveform must be faithfully reproducedby an amplifier.                                                              chronizedwaveforms.
Fig. l3 showsthe testingof sucha circuit usinga triangular
                                                                                                                6. Adjust the CH A and CH B POSITION controls to
wave, such as is typically encountered the recovered
                                                                                                                   superimpose waveforms
                                                                                                                              the        directlyovereachother.
audio output of a limiting circuit which precedesthe
modulatorof a transmitter.                  may
                           The measurement be rnade                                                             7 . Adjust the CH A and CH B verticalsensitivity
using any type of signal;merely use the type of signalfor                                                           (VOLTS/CM and VARIABLE) so that the *aveforms
testing that is normally applied to the ampiifier during                                                            are as largeas possible
                                                                                                                                          without exceeding limits of
normal operation. The procedure for distortion testing                                                              the scale,and so that both waveformsare exactly the
follows:                                                                                                            same height.
 1. Apply the type of signalnormally encountered the
                                               in                                                               8 . Now set the MODE switch to the A-B position (if one
    amplifierundertest.                                                                                             waveform is inverted in relationshipto the other, use
                                                                                                                    the A+B position). Adjust the fine vertical sensitivity
 2. ConnectChannelA probe to the input of the amplifier
                                                                                                                    (CH B VARIABLE) slightly for the minimum re-
    and ChannelB probe to the output of the amplifier.
                                                     [t                                                             mainingwaveform.Any waveform that remains       equals
    is preferableif the two signalsare not inverted in
                                                                                                                    distortion; if the two waveformsare exactly the same
    relationship eachother, but invertedsignals can be
                                                                                                                    amplitude and there is no distortion, the waveforms
    us ed.
                                                                                                                    will canceland there will be only a straighthorizontal
 3. Set CH A and CH B DC-GND-AC       to
                               switches AC.                                                                         line remainingon the screen.

                     I       sranr - .,
                -    ENAELE

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        LINE                                                                                                    '-                                                                      [

                                             I     DATA(s ITS) I
                                                        B              I            D A T A( 8 B I I S )        I                                                                       I
                                         rrllll                                                                                                                                         I
                                             tll                                                                                                                                        I
                                             F-    SECUBIIY ----i      F    SECURITY           SECURITY I                                                                               I
                                         1         DATA 8IT 1              OATAEIT 2           DATA 8IT 3              ]                                                                I
                                                                    MESSAGE FRAME -''- -.'-                                                    LONG BLANK   PULSE _-,--__-----_.1
                                                                                                      __    oNE COMPLETE
                                                                                                            T R A N S M I S S I O NF R A M E

                                         ANY INDIVIDUAL ADDRESS OR FUNCTION
                                         DATA BIT MAY BE POSITIVE OR NEGATIVE
                                         DEPENDING UPON THE CODED INPUT

                                Fig. 12. Family of time-related       from typical digital circuit in Fig. 1l.

                                   A.B = DISTORTION


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                                                                                                             rtPr.rfrt0        Eutsl ( p(}uflly||ytRTt0]
                   AC    I          I   AC
                    A D J U S TS O B O T H                         +2
                    WAVEFORMS RE    A                              0
                    SAMEAMPLITUDE                                  -2
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             Fig. 13. Distortionmeasurement.                                      Fig. 14. Gatedringingcircuit and waveforms.

   The circuit and waveformsof Fig. 14 are shown to
demonstratethe type of circuit in which the dual-trace                                                                                          o(E---:-------l
oscilloscope effectiveboth in design
             is                      and troubleshooting
applications.The basic oscilloscopecontrol settings are           C H A NN E L                                                                  o61                @
                                                                            A                                                                        t\zzf-ii-                1pS/cm
identical to those of Fig. 8. WaveformA is the reference
waveform and is applied to Channel A input. All other
                                                                       P UL S E)
                                                                                                                                  o ['-l@ll
waveformsare sampledat ChannelB and comparedto the
reference waveform of Channel A. The frequency burst
signal can be examinedmore closely either by increasing
                                                                   (O U T P U T
                                                                                                                            __:,@                zL==*ll-
                                                                                                                                     _5sE S L O P E +

                                                                                                                            Lol-,o ?^"'ll
the sweeptime per centimeter .5 mSEC per centimeter
                               to                                   P UL S E }
or by pulling out on the <> POSITIONcontrol to obtain 5
times magnification. This control can then be rotated as
desiredto center the desiredwaveforminformation on the
oscilloscope screen.
   The dual-tracefeature of the oscilloscope     can also be
used to determine the delay times of transmissiontype                                                                           ULTRA SONIC
                                                                           PULSE                                                DELAY LINE
delay lines as well as ultrasonictype delay lines.The input                 GEN
                                                                                                                                  ( 5p Sec)
pulse can be used to trigger or synchronizethe ChannelA
display and the delay line output can be observedon                        5OOOPPS
ChannelB. A repetitivetype pulse will make it possible                     lpSec PULSE                                  WIDTH
synchronizethe displays.The interval between repetitive
pulsesshould be large compared to the delay time to be                                               Fig. 15. Delayline measurements.
investigated.In addition to determining delay time, the
pulse distortioninherentin the delayline can be determined       Typical input and output waveforms are shown on the
by examination of the delayed pulse observedon the               oscilloscopedisplay.Any pulsestretchingand ripple can be
ChannelB waveform display. Figure 15 demonstrates         the    observed and evaluated.The resultsof modifying the input
typical oscilloscope settingsas well as the basictest circuit.   and output terminationscan be observeddirectly.

   A common applicationof the delayline checksis found                       IMPROVING THE RATIO OF
in color televisi,on         Figure 16 shows the oscillo-                    DESIRED TO I.JNDESIRED      SIGNALS
*op. settingsand typical circuit connectionsto check the                         ln some applications,the desiredsignalmay b-eriding on
*y; drluy liie empl-oyed the video amplifiersection.The
                         in                                                   a large undeiired signal component such as 60 Hz. It is
input waveformutiOitt. output waveformare comparedfor                         possibleto minimize or for practicalpurposeseliminatethe             tL,
ariuy time, using the hbrizontal -qVn9 .pulse. of the                         undesiredcomponent.Fig. 17 indicatesthe oscilloscope
compositeuidro signalfor reference.  The indicateddelayis                     control settingi for such an application. The waveform
approximatelyone microsecond. addition to determining
                                In                                            display of Channel A indicatesthe desiredsignaland the
t|6 O.t.y chiracteristicsof the line, the output.waveform                     dofted line indicatesthe average  amplitude variation cor-
 reveals iny distortion that may be introduced from an                        responding an undesired
                                                                                         to              60Hz component.T!..Channel
impedance mismatch or a greatly attenuated output re-                         B display indicates a waveform of'equal amplitude and
 sultingfrom an open line.                                                    identibal-phase the average the ChannelI waveform.
                                                                                             to             of
                                                                              With the MODE switch set to A-B, and by adjusting CH
STEREOAMPLIFIER SERVICING                                                     B verticalattenuator controls,the 60 Hz component the
                                                         is                   Channel  A signalcan be cancelled the ChannelB.inpu-t
   Another convenientuse for dual-channel   oscilloscopes                                                               without the 60
                                                                              and the desiredwaveformcan be observed
in troubleshooting  stereo amplifiers. If identical channel
                                                                              H z component.
amplifiersute ured and the ou_tput one is weak, distorted
or btherwise abnormal, the dual trace oscilloscope becan                      AMPLIFIER PHASESHIFT MEASUREMENTS
efficiently used to localize the defective state. With an                        In the single-trace   application section of this manual
identical'signalapplied to the inputs of both amplifiers, a                   phaseshift measurements     using a singletrace aredescribed.
iide-by-sidi compirison of both units can be made by                          in addition, in the square  wavetestingsection,square  wave
progressivelysampling -identical signal points in both                        distortion is explainedin terms of phaseshift of the signal
i*ftifirtr. When the defectiveor malfunctioningstagehas                       components    which comprisethe square     wave.Thesephase
 been located. the effects of whatevertroubleshooting  and                    shifti can be verified directly by providinga sinewaveinput
 repairmethodsare employed     can be observed analyzed
                                              and                             signal to the amplifier and observing the phase of the
 immediately.                                                                 output signal  with respect the input signal.

                   1 r rS D E L A Y

          C HA ( I N P U T )
                                                                    o                                1pS/cm

        CHB (OUTPUT)                                                @


                                                 @fl@                                                   TO H O R IZ O N T A L A M P L IF I E R .
                                                                                                        N O T E : N O E L E C T R I C A LC O N -
                                                                                                        N E C T I O N ; P L A C E L I PO N
                                                          A&B                                           INSULATIONOF PLATE CAP
                                                                                                        L E A D O R I N C L O S EP R O X .
                                                         .2Y lcm*                                       I M I T Y O F H O R I Z O N T A LA M P -
                                                          CAL                                           L I F I E RT U B E .

                                               S E T B O T H P R O B E SF O R
                                                                                                                           T O V ID E O
                                                 1 O : 1A T T E N U A T I O N
              VIDEO                                                                                                       A M P LF IE R
            A M P L IF I E R
                                                    DELAY L INE

                                                    * N O T E : - S E T T I N GO F V E R T I C A L
                                                      A T T E N U A T O R SS H O U L D B E T H E
                                                      S A M E ,B U T M A Y V A R Y W ID E L Y ,
                                                      D E P E N D I N G N C I R C U I TT Y P E .

                                      Fig. 16. checking "Y" delayline in color televisionreceivers.

                                                                      on 8 cm horizontally. A waveform height of 2 cm is used.
           C H A N N E LA           ADJUST FOR ONE                    The 8 cm display represents 3600 at the pisplayed
                                    C O M P L E T EC Y C L E          frequency and each centimeter represents45o of the
             C H A N N E LB               AT 60Hz                     waveform. The signal developedacrossthe output of the
                                                                      audio amplifier is applied to the Channel B INPUT jack.
                                                                      The verticalattenuatorcontrolsof ChannelB are adjusted
                                                                      as requiredto producea peak-to-peak  waveformof 2 cm as
                                                                      show ni n Fi g. l 88.
                               o                    1mS/cm               The CH B POSITIONcontrol is then adjustedso that the
                                                                      Channel B waveform is displayedon the same horizontal
                               o                    AUTO
                                                                      axis as the ChannelA waveformasshownin Fig. l88. The
                                                                      distancebetween corresponding  points on the horizontal
                               o                                      axis for the two waveformsthen represents phaseshift
                                                                      betweenthe two waveforms. this case, zerocrossover
                               @                                      points of the two waveforms compared. is shownthat
                                                                                                 are             It
                                                    CHA               a difference I centimeter
                                                                                   of            exists.This is then interpreted

                 @fi@                                                 asa phaseshift of 45o.

                                                                      TELEVISION SERVICING
                                                                         Many of the television servicingprocedurescan be
                                                                      performedusing single-trace    operation. Theseare outlined
                                          60 Hz
                                                                      later in the applicationssectioncovering   single-traceopera-
                      START WITH
                         A&B                                          tion. One of theseprocedures,    viewing the VITS (vertical
                      CHANGETO                                        interval test signal), can be accomplishedmuch more
                         A_B                                          effectivelyusing a dual-trace                 As
                                                                                                      oscilloscope. outlined in
                                                                      the single-traceapplications section  and asshownin Fig. 25
                                                                      and 26, the information on the Field #l and Field #2
                                        signal ratio.
   Fig 17. Improving desired-to-undesired                             vertical blanking interval pulseis different.This is shownin
                                                                      detail in Fig. 25. Also, because   the oscilloscope  sweepis
    In all amplifiers,a phaseshift is alwaysassociated with a         synchronizedto the vertical blanking interval waveform,
changein amplituderesponse.      For example,at the -3 dB             the Field #l and Field #2 waveformsare superimposed
responsepoints, a phase shift of 45" occurs. Fig. 18                  onto each other as shown in Fig. 27A. With dual-trace
illustrates a method of determiningamplifier phaseshift               operation,the signalinformation on each blanking pulse
directly.In this particular case, nteasurements being
                                 the                 are              can be viewed separatelywithout overlapping.          Fig. 19
made at approximately 5000 Hz. The input signal to the                indicatesthe oscilloscope   control settingfor viewing the
audio amplifier is used as a reference   and is appliedto the         alternate VITS.
CH A INPUT jack.
                                                                        1. The color television receiver on which the VITS
   The VARIABLE control is adjusted as required to                         information is to be viewed must be set to a station
provide a completecycle of the input waveform displayed                    transmittinga color broadcast.

           A                                                    A D J U S TA S R E O U I R E D
                                                                F O R C O M P L E T EC Y C L E
                                                                            lN Bcm
       C H A N NE L

                        e^3@+@!                                                                  l<-

                                                                  C H A N N E LA                      \   \            /   /
                                                                   C H A N N E LB
                                                                                          /               \       \   a/

                                       AUDIO                   OUTPUT
                                     AMPLI FIER                 LOAD

                                            Fig. 18. Measuringamplifier phaseshift..

2. The control settingsof Fig. 19 are those requiredto                   display to either of the two iields which comprisea
   obtain a 2-fieldverticaldisplayon ChannelA.                           .o*pltt. vertical frame,it cannotbe predicted.which
                                                                         field displaywill appearon the ChannelA or Channel
3. With the oscilloscope and television       operating,
                                       receiver                          B display.
   connectthe ChannelA probe(set at l0: l) to the video
4. Set the SYNC switch as follows:                                    10. Pull the <) POS control outward to obtain an addi-
                                                                          tional 5X magnification. Rotate the control in a
   A. If the sync and blanking pulsesof th-e-    observed                 counterclockwiie direction moving the traces to the
        video signal are positive; use the TV+ switch                     left until the expandedVITS information appears  as
        position.                                                         shownin Fig. 20.
   B. If the sync and blanking pulsesare negative,    use                                       NOTE
        the TV- switch Position'                                          Becauseof the low repetition rate and the high
                                                                          sweepspeedcombinatibn, the b-rightness level of
5. Adjust the sweeptime VARIABLE control so that 2
                                                   screen.                the signaldisplayswill be reduced.
   veriical fields are displayedon the oscilloscope
6 . Connec t he Ch a n n eB p ro b e(s e tto 1 0 :1 )to th e vi deo
                          l                                                                                           havebeen
    detectortestPoint.                                                11. once the channel A and channelB displays
                                                                           identified as being either Field #1 or Field #2 vlTS
7. Set the MODE switch to the A & B position.ldentical                     information,the probe corresponding the waveform
    waveform displays should now be obtained on                            displaywhich is to be used ior signal-tracing     and
    Channels and B.
              A                                                            troubieshooting be used'and the remaining
                                                                                            can                            probe
8. Place the sweeptime VARIABLE control in the CAL                         shouldbe left at the videodetectortest point to insure
    position.                                                              that the sync signal is not interrupted.If -the sync
                                                                           signal is interrupted, the waveform displays may
g. Set the SWEEPTIME/CM control to the .1mS/CM                             re-versebecause. previouslyexplained'there is no
    position. This expands the display by increasing            the        provisionin the oscilloscope identify either of the
    i*.tp speed.  The VITS information will ?Ppear         toward                                            a
                                                                            iwo verticalfieldswhich comprise complete  frame'
    the iight hand portion of the expanded waveform
                                                                          Fig. 20 showsthe dual-trace presentation the Field #1
    displays.The waveforminformation on eachtracemay
    apfeai as shown in the drawing of Fig. 26'..Because               and Field #2 VITS information.The Field #1 information
    th6re is no provisionfor synchronizing oscilloscope
                                                the                   is displayed the trace'


                                                                                      @               START WITH
                                                                                 @      t-o             ( S e et e x t )


                                                                                         o            TV+ or TV-
                                                                                                       ( S e et e x t )


            VERTICAL       VERTICAL
              SYNC         BLANKING

                                                                               VI DEO             PICTURE
                                           VI DEO
                                                                                AMP                TUBE

                            TELEVISION SET

                                    Fig. 19. Set-upfor viewingfields I and 2 of vITS information.

                                                                             presenceof normal signals. This method (signal-tracing)
                                                                             may be usedto tracea signal measuring
                                                                                                       by          severalpointsin
                                                                             the signalpath. As measurementsproceedalongthe signal
                                                                             path, a point may be found where the signaldisappears.
                                                                             When this happens, sourceof troublehasbeenlocated.
                                                                                However,the oscilloscope    shows much more than the
                                                                             mere presence absence signal.It provides peak-to-
                                                                                             or          of                  a
                                                                             peak voltagemeasurement the signal.
                                                                                                         of           The cause poor
                                                                             performance   can often be locatedby makingsuchpeak-to-
                                                                             peak voltage measurements.      The schematicdiagram or
                                                                             accompanying    service dataon the equipment beingserviced
                                                                             usually inciudes waveform pictures. These waveform
                                                                             picturesinclude the requiredsweeptime and the normal
                                                                             peak-to-peak   voltage. Compare the peak-to-peak   voltage
                                                                             readingson the oscilloscope     with those shown on the
                                                                             waveforrn pictures. Any abnormal readingsshould be
                                                                             followed by additional readings the suspected
                                                                                                                in              circuits
    Fig. 20. Oscilloscope presentationof fields I and 2                      until the trouble is isolatedto as smallan areaas possible.
             of VITS information.                                            The procedures maki ngpeak-to-peakolt age easur e-
                                                                                              for                      v      m
                                                                             ments are givenearlierin the CALIBRATED VOLTAGE
                                                                             MEASUREMENT        paragraph.
           SINGLE-TRACE             APPLICATION S
                                                                             COMPOSITEVIDEO WAVEFORM ANALYSIS
                                                                                Probably the most important waveform in television
    In addition to the dual-traceapplicationspreviously                      servicing the composite
                                                                                      is               waveformconsisting the video
outlined,there are, of course,        many service         and laboratory    signal,the blanking pedestalsand the sync pulses. Fig. 2l
applications where only single-trace                 operation of the        and 22 show typical oscilloscope  traceswhen observing
oscilloscope requrred.After gainingexperience
              is                                                 with the    compositevideo signals synchronized with horizontalsync
oscilloscope. userwill be abie to makethe judgmentas
               the                                                           pulses and verticalblankingpulses.
                                                                                                              Composite  videosignals
to whether a job cdn be performed more efficiently by                        can be observed variousstages the television
                                                                                              at             of               receiver
usingthe single-trace the dual-trace
                          or                     methodof operation.         to determine whether circuits are performing normally.
The following are applications which single-trace
                                        in                          opera-   Knowledge of waveform makeup, the appearance a      of
t ion is adeq u a teIn s e v e rac a s e si.t w i l l b e found that an
                                    l                                        normal waveform, and the causesof various abnormal
alt er nat e e th o du s i n gth e d u a i -tra c a p p l icati on been
                                                  e              has         waveformshelp the technicianlocate and correct many
described   for the sameapplication.For all the following                    problems. The technician shouldstudy suchwaveforms a in
applications most flexible operationwill be achieved
              the                                                       iT   televisionreceiverknown 'to be in good operatingcon-
the ChannelB vertical amplifier is used with the MODE                        dition, noting the waveformat variouspoints in thc video
switch in the CH B position. This arrangement                     provides   amplifier.
complete triggered     sweepas well asfree runningoperation
of the oscilloscope,    and, in addition,by placingthe MODE                    To set up the oscilloscope viewingtelevisioncom-
switch in the A-B position (with the CH A DC-GND-AC                          positevideowaveforms, the followingprocedure:
switch in the GND position), whatever waveform is                             1. Tune the television to a localchannel.
obtained can be inverted in polarity if desiredby the
operator.                                                                     2. Set the MODE switchto the CH B position.
                                                                              3. Set the SWEEPTIME/CM switch to the l0 uS/cm
                                                                                 position for observing horizontallines or to the 2
                                                                                 mS/cmpositionfor observing verticalframes.
   A triggered sweep oscilloscope is advantageousin
                                                                              4. Set the SYNCswitchto the TV+ position.
servicingand aligningtelevisionreceivers.
                                        This oscilloscope
also includes severalfeaturesthat were incorporatedto                         5. Set the SOURCEswitchto the CH B position.
make television servicingeasierand more comprehensive.
                                                                              6. Pull the TRIGGERING LEVEL control for automatic
Thesefeaturesinclude :
   o SWEEP TIME/CM control automatically selects
                                                                              7. Set the CH B DC-GND-ACswitch to the AC position.
     verticalsync at sweepspeeds          for
                                appropriate viewing
     frames and horizontal sync at sweep speedsap-                            8. Connect a probe cable to the CH B INPUT jack.
     propriatefor viewinglines.                                                  Connectthe ground clip of the probe to the television
   o Vector overlayfor color demodulator                                         set chassis.With the probe set for 10:I attenuation,
                                                                                 connect the tip of the probe to the video detector
   o Wide bandwidth for high resolutionvideo and pulse                           output of the television
                                                                              9. Set the CH B VOLTS/CMswitchfor the largest
                                                                                                  without goingoff-scale.
VOLTAGE READINGS                                                             10. tf necessary,rotate the TRIGGERINGLEVEL control
   For generaltroubleshooting                                                    to a positionthat provides synchronized
                                                                                                           a           display.
                               and isolationof troublesin
television        (or
          receivers almost any other electronic    equip-                    I l. Adjust the sweeptime VARIABLE control for two
ment for that matter), the oscilloscope an indispensable
                                       is                                         horizontal lines or two vertical framesof composite
instrument. It provides a visual display of absenceor                             videodisplay.

     BURST                       VIDEO

                                                                                                     1 O p rS / c m

                                                                                  I    o

                                                                                      ,El'-          TV-



                                                                 VI DEO               P IC T U R E
                                                                  AMP                    TUBE


                     Fig. 21. Set-up viewinghorizontai
                                    for                               videosignal.
                                                     fieldsof composite

                                                                             oG                      2mS/cm


                      B L A N K IN G

                                                  VI DEO                          P IC T U R E
                                                   AMP                               TUBE

                  T E L E V I S I O NS E T

                         Fig.22. Set-upfor viewingverticalfieldsof compositevideo signal.

t 2 . If the sync and blanking pulsesof the displayedvideo
      signalsare positive, set the SYNC switch to the TV+
      position; if the sync and blanking pulsesare negative,
      usethe TV- position.
13. Pushin the TRIGGERINGLEVEL control and rotate                                                           SYNC PULSE
    to a position that providesa well*ynchronizeddisplay.

14. Adjust the INTENSITY and FOCUS controls for the
    desired         and best focus.
15. To view a specificportion of the waveform,suchasthe
    color burst,pull outwardon the <) POSITIONcontrol
    for 5X magnification.Rotate the samecontrol left or                                                   SYNC PULSE
    right to selectthe desiredportion of the waveform to                                                  COMPRESSION
    be viewed.                                                                                             CAUSED      BY
                                                                                                            L I MI T I N G
16. Compositevideo waveformsmay be checkedat other
    points on the video circuitsby moving the probe tip to
    those points and changing the VOLTS/CM control
    settingas requiredto keep the displaywithin the limits
    of the scale, and by readjustingthe TRIGGERING
    LEVEL control to maintain stabilization. The polarity
    of the observed waveform may be reversedwhen
    moving from one monitoring point to another;there-                                                         ,,WHITE,'
    fore, it may be necessary reverse polarity of the
                              to       the
    SYNC.                                                                                                  SATURATION
                                                                                                           CAUSED      BY
SYNC PULSE ANALYSIS                                                                                         L I MI T I N G
  The IF amplifier response a television
                             of                   can be
evaluated to some extent by careful observationof the
horizontal sync pulse waveform. The appearance theof
sync pulse waveform is affected by the IF amplifier                                                               Fig.24. Syncpulsewaveforms.
bandpass                 Sometypical waveformsymptoms
and their relation to IF amplifier response indicatedin                                         The VITS is transmitted during the vertical blanking
Fig. 23. Sync pulse waveform distortions produced by                                         interval. On the televisionset, it can be seen as a bright
positive or negativelimiting in IF overloadconditions are                                    white line above the top of the picture, when the vertical
showninFig.24.                                                                               iinearity or height is adjustedto view the vertical blanking
                                                                                             interval(on TV setswith internalretraceblankingcircuits,
         qrcUIT             froRtzoilTAL
         O€FECT                PULSE
                                                                     EFFECT N
                                                                      PICTURE                the blankingcircuit must be disabled seethe VITS).

 Normal Crrcutt                                                 Plcture Normal
                                                                                                The transmittedVITS is a precisionsequence specific

                                              .1                                             frequency,amplitude, and waveshape shown in Fig. 25
                                                                                             and 26. The television
                                                                                                                   networksusethe precisionsignals
                                                                                             adjustment and checking of network transmission
                                                                                             ment, but the techniciancan usethem to evaluate television
 Loss ol hrgh frequency                                         Loss ot prcture detarl
 respon$                                                                                     set performance.The first frame of the VITS (line 17)
                                                                                             beginswith a "flag" of white video, followed by sinewave
                                              \                                              frequenci es 0.5 MH z, 1.5MH z, 2MH z,3 MHz, 3. 6 M Hz,
 Excessive hrgh frequency                                       Frne vertrcal black and

 response, non-lrnear                                           whrte stlatrons tollowrrg
 phase shilt                                                    a sharp change In prcture                 I + II T T F L A G
                                                                shadrng                                                                              :ttrt -sQrARt0 RltSt
                                                                                                                               I'5       1.0 ''.2
                                                        A-                                                        I
                                                                                                                  I 0 . , | , . nI l . eI
                                                                                                                                                    (rrAY 8t INTtRCHAXGt0)

                                                                                                                  lT ll lil                               .vlN00u       PuL\t

 Loss of low frequercy                                          Change rn shadrng of large
 respons                                                        prcture areas, smeared
                                                                prcl ure                                                                                                I
                                                                                                                                                                                |    ,,,o, *

                                                                                                                  'l-                                               \
                                                                                                                                                                            H O RI 1 S L A i ( I T i G
                                                                                                                                                                                 P TO t S T A L

             Fig. 23. Analysisof sync pulsedistortion.
   Most network television signalscontain a built-in test                                                                            \
signal (the VITS) that can be a very valuable tool in                                           FttL0 2
troubleshooting and servicingtelevisionsets.This VITS can
localizetrouble to the antenna,tuner, IF or video sections
and showswhen realignment   may be required.The follow-
ing proceduresshow how to analyze    and interpret oscillo-
scopedisplays the VITS.
              of                                                                                                 Fig. 25. VITS signal,fields I and 2.

                                          w r N D O w U t E-
                                                    P S                                  The brightness      level of the signaldisplaywill be
                                     srNE SO,AREO   Or.* -----l
                                                                                         reducedbecause, thoughthe repeti ti onrat e r s
          - r oF r E                            l::l;r ?:::l- -i i' l,i i -t:&3;,
          - ,Jiu                                                           Prcrul
                                                wxr trrac                                o n l v 6 0 H z ( a 1 6 . 0 0 0 S E C p e r i o d tt h e w r i t r n g
                                                                ll   il   vrDEO                                       (.1
                                                                                         speed 20 trrSEC/crn mSECicmmagnified                          fivc.
  a               FIELDIf
                                                                                         ti mes).
                                                                                      8. The waveformshouldbe sirnilarto that shownin Fic.
                                                                                         21. For the osci l l oscope spl ay.each vert icaisvnc
                                                                                         pul sestartsa new sw eep. s causes ne l 7 anil ir ne
                                                                                                                    Thi          li
                                                                                         279 (mul ti -burst) be superi mposed. ar e iines lt
                                                                                                           to                       as
                                                                                         and 280. The rl ul ti -burstsi gnal s i dentr cal.
                                                                                                                             are           whr cli
                                                                                         reinforces trace.However,
                                                                                                   the                   lines 18 and 280 arenot
                                                                                         identicaland both signals superimposed
                                                                                                                     are               over each
              I PUuSES        sYNC
              ]                          PULSES
                                          T -

                            VERTICAL   ELANXING      INTERVAL

     Fig.26. Vertical blanking interval, showing VITS
             inf or m a ti o n .
(3J8 MHz) and 4.2 MHz. This sequence frequencies        of                  is
called the "multi-burst". The first frame of Field #2 (line                                                                                                       I
2 7 9) als oc ont ains n i d e n ti c am u l ti -b u rs t. h i s m ul ti -burst
                      a                  l               T
p o r t ion of t he V IT S i s th e p o rti o n th a t c a n be most
valuableto the technician.         The secondframe of the VITS
(l i nes l8 and 280 ), w h i c h c o n ta i n s e s i n e -s q uared se.
                                                th                      oul
wi n dow puls e an d th e s ta i rc a s e f 3 .5 8 M H z bursts at
p ro gr es s iv ely
                 lighte rs h a d i n ga re v a l u a b l e th e netw ork.
                                       ,                  to
but have less value to the technician.As seen on the
te lev is ion c r een. e l d # l i s i n te rl a c e d i th F i e l d #2 so
             s       Fi                               w
that line l7 is followed by line 219 and line 18 is followed
b y line 280. T he e n ti reVIT S a p p e a rs t th e b o tto m of the
                                                  a                                      Fig.27. Oscilloscope presentation of                             VITS
vertical blanking pulse and just before the first line of                                        information, single- e operation.
vi deo.
   Each of the multi-burst frequencies transmittedat
                                       is                                             9. The presentation the preceding
                                                                                                           of             paragraphs (Fig. 27)
equal strength.By observing the comparativestrengths
                                                   of                                    is the limit of observationpossiblewith a single-trace
thesefrequenciesafter the signalis processed
                                           throughthe                                    oscilloscopy. With the Model 1472C oscilloscope,
teievisionreceiver,the frequency response the set is
                                          of                                             however, a single-field VITS presentation can be
ch e c k ed.                                                                             obtained by placing the MODE switch in the A & B
                                                                                         position. This causesthe ChannelB information to be
     Set up the oscilloscope follows to view the VITS:
                           as                                                            displayedon alternatesweeps, are the Field #1 and
 1 . C o n n e c t h e C H B p r o b e( s e ta t 1 0 : 1 )t o t h e o u t p u to f       Field #2 VITS. Becausethere is no provision for
     t he v ideo det e c to ro r o th e r d e s i re d s t p o i nt i n the
                                                        te                                            the
                                                                                         preselecting Field #1 or Field 1*2rnformation, either
     videosection the television
                       of                    set.                                        Field #l or Field #2 (Fig. 22) will appear. The
                                                                                         multi-burst information in the VITS is the most
 2. If the televisionset has a vertical retraceblankine                                  valuable for troubleshootingtelevision receiversand,
    circuit,bypassthis circuit duringthe measurement.                                    because is presenton both Field #l and Field #2
 3 . S ett he M O DE s w i tc hto C H B .                                                                                           and
                                                                                         VITS, eithercan be usedfor troubleshooting signal
 4. Set up the oscilloscope TV verticaicomposite
                            for                video
    waveformanalysis previously
                       as       described.Two vertical                                  Now to analyze the waveform. All frequencies the
    frames will be visible.                                                          multi-burst are transmittedat the samelevel,but should
 5. Placethe sweeptime VARIABLE control in the CAL                                   not be equally coupled through the receiverdue to its
    position.                                                                        response  curve. Fig. 28 showsthe desiredresponse afor
                                                                                     goodcolor television         identifyingeachfrequency
                                                                                                          receiver,                         of
 6 . Reduc es weep me to .l m i l l i s e c o n d p e re n timeter
                   ti                                c           (.1                 the multi-burst and showing the allowable amount of
     ms/CM) with the SWEEP TIME/CM switch. This                                      attenuation each.Remember
                                                                                                 for                 that -6 dB equals
                                                                                                                                     half the
     glpands the displayby increasing sweepthe            speed.The                  reference voltage(the 2.0 MHz modulationshouldbe used
     VITS information will appear to the right on the                                for reference).
     expanded waveformdisplay.
                                                                                        To localizetrouble, start by observing VITS at the
 7. Further expand the sweepwith the 5X magnification                                video detector.This will localizetrouble to a point either
    (pull outward on the {} POSITION control). Rotate                                beforeor after the detector.[f the multi-burstis normalat
    the {} POSITIONcontrol in a counterclockwise    direc-                           the detector,check the VITS on other channels. some
    tion, moving the traceto the left, until the expanded                            channels look okay but othersdo not, you probablyhave
    VITS appears.                                                                    tuner or antenna-system    troubles. Don't overlook the

                                                                    450   P I CT U R E                                   G RATI CULE            BEZEL
                                                                     I    CARRIE    R

                            '*       {l l
                        -i           -      2o-MH
                                                          - M Io

                   -T!  )              luoJ"o'
                   {i                Lro-nri                    O'5-MHz -i
                   il                         O
                                       MODULATI N              MODULATION

                             l    _ _ 36 - M H z
                                      .                                                  \                                          VECTOR
                                 M O D U LA T I O N                                                                                OVERLAY

                                                                                             \             Fig.29. Installation vectoroverlay.
ct                               MOOULATION
                                                                                                 3 . Adjust the televisionset'shue and brilliancecontrolsto
z                                                                                                    mid-range.
$oo                                                                                              4 . Set SWEEP   TIME/CM control to the CH B position.
                                                                                                 5 , Connectprobe cablesto the CH A and CH B INPUT
                                                                                                     iacks.Chinnel A is the verticalinput and Channel is
                                                                                                     ihe horizontalinput. Connectboth probe tips to the
                                                                                                     driven elementof the red gun, usuallythe grid. If the
                                                                                                     cathode is the driven element,then connect to the
                                                                                                     cathode.(The driveneiementis the elementto which
                                                                                                      the output signal the color amplifieris applied.)
                                                                                                 6 . Adiust the CH A (verticalgain) and CH B (horizontal
                                            43            44                                         gaiir)VOI-TS/CMand VARIABLE controlsro obtaina
                                                                                                     io*or.rt.d 45o pattern that approximatelyfills the
                                                                                                     vector overlay. The oscilloscope now set up tor
            Fig. 28. Color TV IF amplifierresponse                                                   vectorscope  operation.
                                                                                                     For vector presentation,    merely move the horizontal
     chance of the antenna system causing "holes" or tilted                                          orobe to the drivenelementof the blue gun.The color
     response some channels. the VITS is abnormalat the
                on                  If                                                               vector pattern is the same type as given by the
     vid^eo detector on all channels,the trouble is probably in                                      television set manufacturer.Fig 31 shows typical
     the tF amplifier stages.                                                                        displaysobtainedfor setsusing l05o systems      and 90o
         As anotherexample, us assume
                               let            that we havea set on                                    sysiems with either grid drive or cathodedrive.
     the bench with a veiy poor picture.our oscilloscope    shows
     the VITS at the video detectorto be about normal except
     that the burst at 2.0 MHz is low compared the burstson
     either side. This suggests iF trap is detuned_into
                           -out    an                         the
                                                                                                         If the picturetube usescathodedrive,the burst
     passband,   chopping        frequencies  about 2 MHz below
                                                           channel                                    will appearon the right side of the screen'Just
     ihe picture carilei frequency.Switch to                                                          rotate the vectoroverlay180" so the BURSTlabel
     carryingVITS. If the same                  then our reasoning
                                   thing is seen,
                                                                                                      is on the right side.The color bars will then align
     ,s ,igtrtl and the IF amplifier requiresrealignment.If the                                       with the vectoroverlaY.
     poor- responseat 2 MHz is not seen on other channels,
     maybeari ptVttrap at the tuner input is misadjusted,  causing                                       The vector display provides a very quick
      a bite on only one channel.Other traps at the input of the                                      measurement the functionsof the demodulators
      set could similarlybe misadjusted faulty.
                                          or                                                          in a color TV set. The serviceman   should famil-
                                                                                                      tarrze himself with the effect on the pattern
         If the VITS response the detector output is normal
                                 at                                                                                                  He
                                                                                                      producedby the color controls. shouldobserve
      for all channels, th-etrouble will be in the video amplifier.                                   ihat the color amplitudecontrol will vary the size
      L,ook for open peaking coils, off-value resistors,solder                                        of the petals but not their position. The hue
      bridges across patterns,
                     foil          etc.
                                                                                                      control changes positionof the petalsbut not
                                                                                                      their amplitude.Lastly, l05o sets will havea more
     VECTORSCOPEOPERATION                                                                             elliptical pattern than 90o sets.The table below
                                                                                                      listssomecommontroubles     and their effect on the
        Performance  testingand adjustmentof the color circuits                                       pattern.
     in color television receiversis simplified by using thg
     vectorscope  operationof the oscilloscope.    The additional                                         The vector display can be used to check the
     equipment needed is a color bar generator' The                                                    rangeof the color set'shue control. It shouldbe
     B'&^K-Precision  color bar generators ideallysuitedfor
                                            are                                                        possible rotate the R-Y petal about the vertical
     this.                                                                                             axis. At the center of the hue control the R-Y
                                                                                                       petal should be vertical. If it is not, locate the
        First the horizontal and verticai gain of the oscilloscope                                     CHROMA referenceoscillator.[n most setsthis
      must be equalized(seeFig. 30).                                                                   oscillator transformer-coupled the demodula-
                                                                                                                 is                     to
       1. Attach vector overlay to scope.Pull off bezcl, insert
          overlay, re-attach bezel- (Refer to MAINTENANCE                                                 A slight touch-up of this transformer all that
          AND CnftgRATION section for graticuleremoval')                                               is necesiaryto bring the R-Y petal to a vertical
       2. Connectthe color bar generator the television
                                             to             set                                        position. Do not attempt to make any
                                                                                                       ments on the chroma bandpass       amplifiers'This
          and tune in the color bar Pattern.


                                                                             o             @

                                                                             o             I
                                                                             @             l@,


                                                                  ADJUST A

                  BAR                CHASSIS
               GENERATOR                                           GREEN

                      Fig. 30. Equalizinghorizontal and verticalgain for Vectorscope

amplifier is aligned by a sweep generatorand                                     NOTES
c-annotin generalbe aligned by just a vector
   If the sethasadjusteddemodulators, vector
display can also be used for demodulatoralisn-
ment. Follow the manufacturer's   alignmentpio-
cedure to locate the proper coils and insteadof
countingbars simply adjust for the correctangle
between  R-Y and B-Y.

       G R ID                                              CATHODE
       D R IV E                                             D R IV E                                            --------Rt

                                                                                                                ffilllil ['-l e
      R-Y F=\

                                          ,"=Rvr                                                                         o
                                             \ 6/U\
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                                                                                                                fflu Ol^t
    V E C T O R D I S P L A Y F O R 9 0 " P I C T U R ET U B E                                     ": /A\
       G RI D                                             CATHODE                                   I                                                         U
       DRIVE                                               DRIVE

      R-Y,*-_-                                             NA|         ,/1
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                                                   4{                      \
                                                           " [,)\
  V E C T O R D I S P L A Y SF O R 1 0 5 "P I C T U R ET U B I

                                      COLOR                                                                                     BLUE                PICTURE
                                       BAR                                      CHASSIS                                                              TUBE
                                    GENERATOR                                                                                 G REEN

TROUBLE                                                      E F F E C TO N P A T T E R N                                     EFFECT ON T.V. PICTURE

L o s so f c o l o r s y n c                                 P e t a l so f p a t t e r n w i l l r o t a t e                 V a r y i n gc o l o r s
O v e r l o a d i n g f c o l o r a m p l i fi e r s
                     o                                       P e t a l sa r e c r u s h e do r f l a t t e n e d              Color distortion
C o l o r a m p l i fi e r su n b a l a n c e d r
                                               o             F l o w e r p a t t e r nv e r y e l l i p t i c a l             Color distortion
L a c k o f r a n g eo f h u e c o n t r o l                 R-Y petal cannot be madeto be                                    Hue control won't adjust
                                                               vertical                                                         fleshtones
D e m o d u l a t o ro u t o f a l i g n m e n t             Angle between R-Y petaland B-Y                                   Wrong colors
                                                               petal not to manufacturer's
                                                               specifcation (90" or 105'
                                                                        S     f
                                                               General peciication .)

                                             Fig. 31. Vectorscope
                                                                operationand patterns.


                                              TELEVISION    ALIGNMENT

INTRODUCTION                                                                           NOTE
                                                                 For a comprehensive    analysisof televisionalign-
   Alignment of tuners, the video IF strip, and chroma
circuits in television receiversrequires a high quality
                                                                 ment, we recommendthe instruction manual for
                                                                 the B & K Model 415 Sweep/Marker        Generator.
oscilloscope,suchas this instrument.The additional pieces
of test equipmentrequiredare sweepgenerators video
                                               for               This "handbook of televisionalignment" includes
sweep, sweepand RF sweep,
       IF                       markergenerators, bias
                                                 DC              not only the procedures using the instrument,
                                                                 but all the how and why answers     about television
supplies and a VTVM. The sweep generatormethod ,of
                                                                 alignmentin general.  Even if you use other sweep
aligrment displaysa bandpass  responsecurveon the screen
                                                                 generators,this comprehensive     manual provides
of the oscilloscopeof the type always shown in theory
                                                                 valuable procedures,insights and tips that will
books and in the televisionset manufacturer'salignment
                                                                 make alignmenteasierand more professional.     The
instructions(typical responsecurvesare shown in Fig. 32).
                                                                 many.illustrationsand easy-to-understand    step-by-
                                                                 step approach qualify it as the "how to align"
                                                                 textbook. Copies are available from your
       f5   74   75   7?   70   69                               B & K-Precision distributor or the factory.
       38   39   40   4r   4l   44

                                                             IMPORTANCE OF SWEEPALIGNMENT
                                                               The most rapid way to determinethe overall condition
                                                            of the tuner, IF and chroma portions of the television
                                        A M P LI T U O €    receiver is to provide a constant-amplitude  signal which
                                        R_F SWEEP
                                                            sweepsthrough the entire bandwidth of a given television
                                                            channelat a controlled,repetitiverate. As this signalis
                                                            processed  through the tuned portionsof the receiver, is
                                                            shaped the gain and bandpass
                                                                   by                         properties the various
                                                            sections.Because signalis channeled
                                                                              the                  from one series   of
                                        OV€RALL TUN€R       tuned circuits to anotherit is important that eachsection
                                                            has the proper characteristics. fhe signalis demodulated
                                                            at certain points and the envelopeobserved,   the gain and
                                                            bandwidth propertiesup to that point can be determined.

                                                               Fig. 32 shows the sweep signal with basic response
                                                            curves of the tuner, IF amplifiers and chroma bandpass
                                                            circuits below it. The bandwidthsshownare approximately         -
                                        CXROYA TAXE_OFF
                                                            to scale.Theseoutlines are similarto the curvesthat would       -
                                        COIL RESPONSE       be obtainedif the outputs of the varioussections the TV
                                                            receiverwere demodulatedand the curye observedon an
                                                            oscilloscope.Because the relativebandwidths,the tuner
                                       OVERALL CINOilA
                                                            response leastcritical.
                                                               Some referencefrequencies     are identified to show the
                                                            importance of proper alignment.Notice that the chroma
                                                            frequencies on the slopeof the IF response
                                                                        are                                   curve.This
                                                            area is the most critical because  improper IF alignmentin
                                                            this areawill affect the amplitudeand shapeof the chroma
                                                            response  curveand this in turn affectscolor picture quality.
                                                               Notice that the chroma information is located on a
                                                            constant-amplitudeportion of the transmitted television
     Fig. 32. TV response curves obtained by sweep-         spectrum.  Notice that the relativeamplitudes the chroma
              frequencytechnique.                           information are modified by passingthrough the tuned
                                                            circuits of the televisionreceivertuner and IF amplifiers.
                                                            This is shownby reference the overallIF response
                                                                                        to                        curve.
   The ideal instrumentsfor televisionalignment are this    Notice that the signalinformation at the uppei end of the
oscilloscope and the B & K-Precision Sweep/Marker           chroma frequency range (4.08 MHz) is reduced in
Generator.  The B & K-Precision Sweep/Marker Generator      amplitudewith respectto the signallevel at the lower end
providesall necessarysweepranges,markers and DC bias        of the chromafrequencyrange(3.08 MHz). To compensate
voltages, from one instrument.The simplifiedoperating
         all                                                for this frequency-versus-amplitude    characteristicof the
procedureand calibratedaccuracy the instrumentresults
                                 of                         overall IF responsecurve, a chroma takeoff coil is used
in precisionalignment.                                      between the IF output and the bandpass     amplifier of the
                                                            chroma portion of the receiver.   The chroma takeoff coil is
   For complete alignment instructions of each particular   tuned to the upper end of the chroma frequency range,
televisionset, follow the manufacturer's            How-
                                                            yryally 4.08 MHz and providesa response shownin Fig.
ever,the following general set-upinstructionsdemonstrates   32. This compensates    for the amplitude-versus-frequency
useof the oscilloscope sweep-frequency     alignment.       characteristicof the chroma portion of the overall If;
   In this manual,only the proper useof the oscilloscope
                                                       in             curve. The resultof combiningthe response the
televisionis emphasized. Proper use of the sweepgenerator
                                                            IF curve and the response the chroma takeoff coil is to
                                                                                        of                                  !
and other equipment required for alignment should be        produce g q4 overall response the chroma frequency
provided in the instruction manualsfor those instruments.   range(3.08 MHz to 4.08 MHz). The resultantsignalis their

applied to the bandpassamplifier which has the response             givenfor the link circuitsby somemanufacturers.
indicated the overallchromaresponse  curve.                            Once the deficient portion of the receiver determined,
   Alignment of the chroma takeoff coil is sometimes                an alignmentcheck of that sectioncan be performed.The
specifiedas a separatestep in manufacturer's  test pro-             aiignment procedures vary with manufacturers. Some
;edures.[n other procedures, adjustmentof the chroma                suggest signalcombinationsat the tuner antennaterminals
iakeoff coil is performedtogetherwith the adjustment of             which can generateIF and video sweepfrequencies the  in
the bandpass  transformer.                                          receiverso that overall alignmentcan be done by selecting
                                                                    the right combination of input signals. One way of doing
SWEEP   AI,IGNMENT METHODS                                          this is to tirst connect an RF sweep generatorfor IF
   The best methodof checking alignment  and determining            alignment. After this is compiete, the picture carrier
*'hich stages require alignmentis to inject an RF sweep             frequencyfor the channelbeing used is selected   and this is
irequencysignalat the tuner antennaterminals.  The AGC              modulated by a video sweep signal(this is the VSM, or
bias line must be clamped by application of bias or                 video sweep modulation method). This video sweep
grounding  the AGC line.The outputsof the [F and chroma             modulationis demodulated the videodetectorof the TV
circuitsaie then observed an oscilloscope compared
                          on               and                      receiverand appliedt'o the chromabandpass   circuitsfor the
to the manufacturer'srecommended   response curye.                  alignmentof thesestages.
   The techniciancan then decide which portions of the                 Other manufacturers recommend [F sweepfrequency
receiver requirealignment.For example, the [F response
                                       if                           injectedat the mixer grid (or base,if transistorized) IF
rs satisfactorybut the chroma responseis not. then the              alignment. The [F picture carrierfrequency (45.75MHz) is
problem is between the video detectoroutput of the IF               then modulatedwith a video sweep   voltage(VSM again).As
strip and the output of the bandpass amplifier" if the IF           before this is detectedat the video detector of the TV
response  and the chroma response poor then it is most
                                 are                                receiverand the recoveredsweepvoltage is used for the
likely that the IF requires touch-up, particularly if the           chromacircuit alignment
response poor on the slopeaffectingchromaresponse.
          is                                                           Another method is to first video-sweep align the chroma
   The RF portion of the tuner seldom createsan align-              circuits directly. The IF is then alignedand video sweep
ment problem because passband so much greaterthan
                      the          is                               modulationof the IF pix frequency   (45.75 MHz) is usedto
that of the IF section;however,the mixer output circuit,            check the combined effect on the chroma response IF   of
which is locatedon the tuner, may requireattention.This is          alignmentand chromaalignment.Usuallya touch-upof the
part of the tuned matchingnetwork betweenthe tuner and                                             to
                                                                    chroma circuits is necessary obtain the desired final
the first IF stage.A separate  pre-alignment procedureis            overallchromaresDonse.


                                                                                        o6            @        CHB

                                                                                        o l*=lq
                            SWEEP/MA R KE R                                             @             lO,
                             GENERATO R

                             RF     SWEEF
                            OUT   VOLTAGE

            TERMINALS                         M IXER
                                                                       .01V/cm     ADJUST
             SELECTO R       !
               <r62          I

             "V.5t '
               ere                 TELEVISION ET

                                            Fig. 33. Typical tuner alignmentset-up.

   In conjunction with If alignment,practicallyall manu-               sweepgeneratorat low level to avoid overloading the
facturersrecommendpre-tuningIF traps by injecting spot                 television receiver,which would distort the response
frequenciesinto the IF (usually at a specifiedtuner test               curveand providean erroneous picture of alignmenton
point). Other proceduresoutline a prealignment of all                  the oscilloscopescreen.
tuned circuits in the IF before sweepalignmentprocedures.
                                                                     5. The oscilloscope sweepand sweep generatormust be in
   In all cases manufacturer's
               the               method is the best for his             exact synchronizationand phasewith each other for
particular receiverand the manufacturer's                               proper presentation. the response
                                                                                            of           curve.This is easily
preferred for alignment. SAMS PHOTOFACT procedures                      accomplishedfor sinusoidal or sawtooth sweep by
are alsoreliableand in most casesrepeatthe manufacturer's               lgtltlg the oscilloscope external horizontal input
procedure. If complete realignment of an apparently                     (SWEEP TIME/CM to CH B,position)and connectlng
deficient receiver does not restore the requirediesponse,               the horizontal sweepvoltagefrom the sweep  generator
the technicianmust then considerthat a componentiailure                 to the Channel B input terminalon the oscilloscope.
has occurred and must employ standardtroubleshooting                 6. Select the marker generatorfrequenciesrequired to
procedures.                                                             measure upper and lower response the tuner.
                                                                                the                      of
TLJNERALIGNMENT (Refer to Fig. 33)                               7. The tuner responsecurve is now displayed on the
                                                                                See the manufacturer'sinstructions for
 1. Connect the output of the sweep generatorto the                 the responsecurve specificationsand the necessary
    antenna terminals of the television set. Adjust the             adjustments realignment.
    sweepgenerator sweepone of the TV channels.
 2. Tune the TV set to the samechannel.                          IF ALIGNMENT (Refer to Fig. 34)
 3. Connect the ground clip of the oscilloscope    probe             l. Connect the output of the sweepgeneratorto the
    directly to the tuner shield to minimize hum pickup.                signalinjection point of the mixer. Adjust the sweep
    Connect the Channel A (Vertical) probe (set to                      generator to sweep the tF frequency band. (If the
    DIRECT) to the tuner test point. The tuner test point               tuner has been properly aligned, RF sweep may be
    is_normally the grid of the mixer tube or equivalent,               appliedat the antennaterminals)
    wherea demodulated   signalis present.
                                                                 2. Synchronize the oscilloscopesweep with the sweep
4. Set the vertical controls (CH A VOLTS/CM and                     generator as previously described in the TUNER
   VARIABLE) for maxirhum sensitivityand operatethe                 ALIGNMENT procedure.

                                                                                     OA                  CHB
                                                                                     o           t

                    RF          SWEI
                    OUT        VOLTI

                                                                       .01V/cm     ADJUST


                                                                       VI DEO


                                        Fig. 34. Typical IF alignmentset-up.

       Connect the ground clip of the oscilloscope             4. Use a demodulator probe for the vertical input
       probeto the television chassis.                             (ChannelA) to the oscilloscope. Measure  the response
                                                                   curveat the input to the demodulators.
t-     Connectthe verticalprobe of the oscilloscope the
       v ideodet e c to r u tp u t.
                        o                                                                                         (CH
                                                               5 . Set the verticalgaincontrolsof the oscilloscope A
                                                                   VOLTS/CM and VARIABLE) for a convenient       viewing
        Set the vertical gain controls(CH A VOLTS/CM and           sizeon the screen.
        VARIABLE) for suitable viewing of the response
        c ur v e.                                              6 . A responsecurve similar to that shown in Fig. 37
                                                                   shouldbe seen.Select  the markergenerator
 (-r    Keep the sweepgenerator   output levellow to prevent                                                      for
                                                                              Refer to the manufacturer's
                                                                   of interest.
        overloading. Follow the manufacturer's  recommenda-        bandpass               and
                                                                            specifications alignment  procedure.
        tions on disablingAGC.
 1 . Select the marker generatorfrequencies  required to
     checkthe critical frequencies interest(seeFig. 35).
     A sweepand markergenerator   capable displaying
                                          of         all
     the markers simultaneously, such as the                                                        _    3.58 MHZ
     B & K-PrecisionModel415, is a big advantage.
 x                              instructionsfor evaluating
        Follow the manufacturer's
                                                                     3 . O BM H Z - l
                   curveand making the alignment.
        the response
                                                                                                                    4 . O 8M H Z

                                                                                        I                    I

                                                                 9e/" *lo"/"


         5o"/"                                                                              t-_  VALLEY
                          I                                                                                          i
                                                                                                t5"/" MAX
           -^/ I                                                                              TI L T I O T OM A X
                                                                                                    4 so MHz---]

         souND       I         I
         .?5 MHZ -----)

                                                                 Fig. 37. Typical chroma responsecurve, showing
           42.t7 MHZ           I                                                  ranges response
                                                                          tolerance    of        levels.

       Fig. 35. Typical IF responsecurve,showingtolerance                                     NOTES
                ranges response
                      of         levels.

CHROMA ALIGNMENT (Refer to Fig. 36)
   The IF alignment must be satisfactorily completed
before startingthis chroma alignment procedure. direct
urjectionof video sweepis used rather than the IF sweep
injection specified herein, the responsecurve is altered
drastically.Follow the manufacturer'sprocedureexplicitly
for such direct injection of video sweep for chroma
 l. lrave the sweep/marker   generator and AGC bias
    connected for IF alignment. the sweep
              as               Set           generator
    to sweep approximately the 4l to 44 MHz band of
    frequencies.Use the sametF injection level that was
    usedfor IF alignment.
 2. Apply the proper DC bias to the color killer to enable
    the color amplifiers(bandpassamplifiers).Refer to the
    manufacturer's instructionsfor the correct bias level.
 3. Synchronize the oscilloscope sweep as previously
    described tuner alignment.


                                                 @G             @
                                                      t                CHB

                                                 o l=-lg  LE=-@,

                              0          !                !U
                              U            U

      GENERATOR                           ADJUST
                               VERTICAL HORIZONTAL
                                 SIZE      SIZE
            VO LTAG E


                           VIDE,O      VI DEO   DEMODULATOR
                         DETECTOR       AMP        PROBE

                                  FI RST         COLOR AMP
                               COLOR AMP         (BANDPASS          DEMOD

            TELEVISION                                KI LLER

            Fig. 36. Typical chromaaiignmentset-up.


                                                                                    -------- Ell
                                                                                  " liTftl f-LL
                                       -trR                                                                                            CHB
                                   /            \
                               f                    t

                                                                                  llfi-i :rYrrll
                           I                            \                         \\4t

                                                                                                                       U       @

                                                                                                 VERTICAL   HORIZONTAL
                      MARKER                                                                       SIZE        SIZE
                                              MARKER               RF    SWEEP
                                               I NPUT             OUT   VOLTAGE

                                                                                                                     DI RECT
                                                    MIXER                           DEMODULATOR

                                                        FM    RECEIVER

                                                            Fig. 38. TypicalFM receiver

                FM RECEIVER ALIGNMENT                                                             should appear exactly in the center (seeFig. 38B).
                           Refer to Fig. 38                                                       Adjust the demodulator according to the manu-
                                                                                                  faciurer's instructions so the marker moves equal
    P r oc edur e:                                                                                distances from center as the marker frequency is
                                                                                                  increased and decreased  equalamountsfrom the 10.7
     1. Connect a sweepgeneratorto the mixer input of the                                         MFIzcenterfrequency.
        FM receiver.Set the sweepgenerator a 10.7 MHz
     2. Connect the sweep voltage output of the sweep                                                       PHASEMEASUREMENT
        generatorto the Channel B input jack of the oscillo-
        scope and set the oscilloscopecontrcls for external                                     Phase measurements be made with an oscilloscope.
                        (SWEEP  TIME/CM to CH B).                                            Typical applications                           producea
                                                                                                                 are in circuits desigrred,to
     .)                                                                                      spetific phase shift, and measurementof phase shift
          Connect the vertical input probe to the demodulator                                distortion in audio amplifiers or other audio networks.
          input of the FM receiver.                                                          Dstortion due to non-linear amplificationis alsodisplayed
     4 . Adjust the oscilloscopevertical and horizontal gain                                                   waveform.
                                                                                             in the oscilloscope
         controls for display similar to that shownin Fig. 38A.                                 A sine wave input is applied to the audio circuit being
                                                                                             tested. The samesine wave input is applied to the vertical
     5. Set the marker generatorpreciselyto 10.7 MHz. The
                                                                                             input of the oscilloscope,   and the output of the tested
        marker "pip" shouldbe in the centerof the bandpass.                                  circuit is appliedto the horizontalinput of the oscilloscope.

t    6. Align the IF amplifiersaccording the manufacturer's

     7. Move the probe to the demodulator   output. The "S"
                                                                                             The amount of phase differencebetween the two signals
                                                                                             canbe calculated   from the resultingwaveform.
                                                                                                                         use the following pro-
                                                                                               To make phase measurements,
        curve should be displayed.  and the 10.7 MHz "pip"                                   cedure(Refer to Fig. 39).

                         S IG N A L
                                                                                                         @                     CHB

                                                                  ffi                                      [.
                                                                  ffi                               o      I
                                                                                                              cr'    I

                                                                           VERTICAL HORIZONTAL
                                                                             SIZE      SIZE

                                                          N E T W O RK
                                                       B E I N GT E S T E D

                                      Fig. 39. Typical phasemeasurement

l . Using an audio signalgenerator
                                 with a pure sinusoidal
     signal,apply a sine wave test signalat the desiredtest
     frequencyto the audio network beingtested.
2 . Set the signal generator output for the normal
                                                                        N O A M P L I T U D ED I S T O R T I O N    AMPLITUDE DISTORTION
     operatinglevel of the circuit being tested.If desired,                  NO PHASE SHIFT                           NO PHASE SHIFT
                  output may be observed the oscillo-
     the circuit'sr                         on
     scope.If the test circuit is overdriven,the sine wave
     display on the oscilloscope clipped and the signal
     levelmust be reduced.
3 . Connectthe ChannelB probeto the output of the test
4. Set the SWEEP TIME/CM control to CH B.
                                                                                                                    NO AMPLITUDE ISTORTION
5 . Connect the Channel A INPUT probe to the input of                         ISoO oUT OF PHASE
                                                                                                                          P H A S ES H I F T
     the test circuit.(The input and output test connections
     to the vertical and horizontal oscilloscope inputs may
     be reversed.)
6 . Adjust the ChannelA and B gaincontrolsfor a suitable
7 . Some typical results are shown in Fig. 40. If the two
     signals in phase,the oscilloscope
           are                           trace is a straight
     diagonal line. If the vertical and horizontal gain are              A M P L I T U O EO I S T O R T I O N
                                                                                                                         90" oUT oF PHASE
     properlyadjusted, line is at a 45" angle.
                        this                                                   P H A S E S H IF T
     A                                                                  Fig.40. Typical phase measurement oscilloscope
       .90o phase shift produces a circular oscilloscope
     pattern.                                                                   displays.

         Phase shift of less (or more) than 90o produces an
     elliptical oscilloscope
                           pattern. The amount of phaseshift                           UNKNOWNEqUENCY
                                                                                                   FR                             R A TO O F
     can be calculatedfrom the oscilloscope trace as shown in
     F i g .4 1 .                                                                                I
                                                                                       T O V E R TC A L I N P U T ,               UNKNOWN
                                                                                       STANDARD EqUENCY                               TO
                                                                                       T O H O RZ O N T A LN P U T
                                                                                               I           I                      STANDARD

                                                                                      sEE-"'((                                       ,-r: I
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                                                                                      sEE                                            l:1

                                                                                                                                    lta:   I

                                             6 _A                                                                                    6:l
                                    RE       il   = PHASE NGLE
                                                                                      N O T E : A N Y O N E F T H E S EF I G U R E S E P E N D I N G
                                                                                                          O                         D
                                                                                                U P O NP H A S E E L A T I O N S H I P
                      Fig.4l. Phase
                                  shift calculation.
                                                                                     Fig.42. Lissajous waveforms used for frequency

                                                                                      As statedbefore,a square                   a
                                                                                                                 wavecontains largenumber
     Procedure:                                                                                       By
                                                                                  of odd harmonics. injectinga 500 Hz sinewaveinto an
                                                                                  amplifier, we can evaluateamplifier response 500 Hz at
       1. Connectthe sinewaveof known frequencyto the CH                          only, but by injectinga square   waveof the samefrequency
          B INPUT jack of the oscilloscope set the SWEEP
                                         and                                      we can determine how the amplifier would respond to
          TIME/CM control to CH B. This provides external                                        from 500 H z up to the l 5th or 2 lst har m onic.
                                                                                  i nput si gnal s
                                                                                     The need for square waveevaluationbecomes   apparent
      2. Connectthe verticalinput probe(CH A INPUT) to the                        if we realizethat some audio amplifierswill be required
         unknown frequency.                                                       during normal use to pass
                                                                                                          simultaneously largenum6erof
      3. Adjust the Channel A and B size controls for a                           different frequencies.With a square wave, we have a
                   easy-to-read of display.
                              size                                                controlledsignalwith which we can evaluate input and
                                                                                  output quality of a signal of many frequencies(the
      4. The resulting pattern,calleda Lissajous
                                               pattern,shows                      harmonics the square
                                                                                             of          wave)which is what the amplifier
         the ratio between two frequencies. Fig.42.
                           the                See                                 sees when amplifying complex waveforms of musical

                                                                                  instruments voices.

                                                                                     The square  waveoutput of the signalgenerator  must be
                                                                                  extremely flat so that it does not contribute to any
                                                                                  distortion that may be observed when evaluating  amplifier
                                                                                  response. The oscilloscope verticalinput should be set to
     INTRODUCTION                                                                 DC asit will introducethe leastdistortion,especially low
         A squarewave generatorand a low-distortion oscillo-                      frequencies. When checking amplifier response,    the fre-
     scope, such as this instrument, can be used to display                       quency of the squarewave input shouldbe variedfrom the
     varioustypesof distortionpresentin electroniccircuits.A                                                       up
                                                                                  low end of the amplifierbandpass towardthe upperend
     squarewave of a given frequencycontainsa largenumber                         of the bandpass; however, because the harmoniccontent
     of odd harmonicsof that frequency. If a 500 Hz square                        of the square  wave,distortionwill occur before the upper
     wave in injected into a circuit, frequency componentsof                                                   is
                                                                                  end of the amplifierbandpass reached.
      1. 5 k Hz , 2. 5k H 2 ,3 .5 k H z , a l s oa rep ro v i d e dS i nce
                                                                   .     vacuum      It shouldbe noted that the actual responsecheckof an
     tubes and transistors non-linear, is difficult to amplify
                                are                  it                           amplifiershould be made using a sinewavesignal.    This is
     and reproducea square          wavewhich is identicalto the input            especiallyimportant in limited bandwidthamplifiers  (voice
     signal.Interelectrode        capacitances,       junction capacitances,      amplifiers).The squarewave signalprovidesa quick check
     stray capacitances well aslimited device
                             as                                 and transformer   of amplifier performanceand will give an estimate of
     responseare a few of the factors which prevent faithful                      overall amplifier quality. The squarewave also will reveal
     reproduction of a square wave signal. A well-designed                        some deficiencies  not readily apparentwhen using a sine
     amplifier can minimize the distortion caused by these                        wave signal.Whethera sine waveor square  waveis usedfor
     limitations. Poorly designedor defective amplifiers can                             the
                                                                                  testing amplifier,it is importantthat the manufacturer's
     introduce distortion to the point where their performance                                  on
                                                                                  specifications the amplifierbe known in order to make a
     is unsatisfactory.                                                           betterjudgmentof its performance.

TESTING PROCEDURE(Refer to Fig. 43)                          maximum amplitude to zero amplitude at the l80o or
                                                             half-cycle point. Therefore, a theoretical reduction in
 1. Connect the output of the squarewave generator
                                                 to          amplitudealone of the high frequencycomponentsshould
    the input of the amplifier beingtested.                  producea rounding of the squarecornersat all four points
 2. Connectthe CH B testprobeof the oscilloscope the
    output of the amplifierbeingtested.
                                               to            of one squarewavecycle(SeeFig. ).                                 v
 3. tf the DC component of the circuit being testedis
    sufficiently low to allow both the AC and DC
    componentto be viewed,use the DC positionof the
    AC-GND-DCswitch. However,the AC position may be
    used without affectingthe resultsexcept at very low
    frequencies (below 5 Hz).
 4. Adjust the vertical gain controls for a convenient
 5. Adjust the sweeptime controlsfor one cycle of square
    wavedisplayon the screen.
 6. For a close-upview of a portion of the squarewave,
    usethe 5X magnification.

   The short rise time which occursat the beginning the
half-cycleis createdby the in-phasesum of all the medium
and high frequencysine wave components.    The sameholds            Fig.44. Squarewave response
                                                                                              with high frequency
true for the rapid drop at the end of the half-cyclefrom                    l oss.

                                                                               @                        A D J U S TS W E E P

                                                                               o                         S P E E DF O R 1

                  SQUARE WAVE                                                          rll-lr   I         SLOPE +
              o                   o                P^fr                U                            @


                                                                       A D J U S TV E R T
                                                                         GAIN FOR
                                                                       CONVENI NT

                                 l   INPUT
                                                 A M P L IF I E R
                                                BEING TESTED

                            Fig. 43. Equipmentset-upfor squarewavetestingof amplifiers.

                          into threedistinctcategories:
Distortioncan be classified

 t .   The first is frequency distortion and refers to the
       changefrom normal amplitudeof a componentof a
       c om plex a v e fo rm. o th e rw o rd s ,th e i n troducti onn
                 w          In
       an amplifier circuit of resonantnetworks or selective
       filters createdby combinationof reactive           components
       will createpeaksor dipsin an otherwise          flat frequency
       response  curve.
 2. The second is non-lineardistortion and refers to a                                tt,
       changein waveshape produced by applicationof the                               z
       waveshape non-linear
                 to                      or
                             components elements      such                            c
       as vacuum tubes,an iron core transformer, and in an                            ur
       extremecase,a deliberate non-linearcircuit suchas a                            a
 3. The third is delay or phase distortion, which is
    distortionproducedby a shift in phasebetweenone or
    more components a complexwaveform.
   in actualpractice,a reductionin amplitudeof a square
                                                                                      Fig. 45. Response  curve of amplifier with poor low
wavecomponent(sinusoidal   harmonic) usuallycaused
                                      is               by
                      network which includes capacity,                                         and high ends.
a frequency-selective
inductance both. The presence the C or L introduces
           or                  of                       a
differencein phase angle between components,      creating
phasedistortion or delay distortion.Therefore,in square
wavetestingof practicalcircuitry, we will usuallyfind that
the distorted square wave includes a combination of
amplitude and phasedistortionclues.
     ln a typical wide band amplifier,a squarewavecheck
accuratelyrevealsmany distortion characteristics the                       of
c ir c uit .T he r e s p o n s o f a n a m p l i fi e r s i n d i c atedn Fi g.45.
                               e                      i                i
revealingpoor low-frequency response                          along with over-
compensated        high-frequency        boost. A i00 Hz square              wave
appliedto the input of this amplifierwill appearas in Fig.
46A. This figure indicatessatisfactory                      medium frequency            t o 0H z                  I KHZ
response      (approximately1 kHz to 2 kHz) but showspoor
low frequency response.               Next, a 1000 Hz squarewave                      SOUARE
appliedto the input of this same                amplifierwill appear in       as                                  SOUARE
Fig. 468. This figure displaysgood frequencyresponse                             in    WAVE                        WAVE
the region of 1000 to 4000 Hz but clearly revealsthe
overcompensation the higher10 kHz regionby the sharp
riseat the top of the leadingedgeof the square                        wave.
   As a rule of thumb, it can be safelysaidthat a square
wavecan be usedto reveal    response phase
                                    and       relationships                           Fig.46. Resultant100 Hz and 1 kHz squarewaves
up to the 15th or 20th odd harmonicor up to approx-                                           from amplifier i n F i g . 4 5 .
imately40 timesthe fundamental the square
                                 of            wave.Using
this rule of thumb, it is seenthat wide-band  circuitry will
requireat least a two-frequencycheck to properly analyze
the completespectrum. the case
                         [n         illustrated Fig. 45, a
100 Hz squarewave will encompass        componentsup to
about 4000 Hz. To analyzeabove 4000 Hz and beyond
10,000Hz, a 1000 Hz squarewaveshouldbe satisfactory.

   Now, the regionbetween100 Hz and 4000 Hz in Fig. 45
shows a rise from poor low-frequency responseto a
flatteningout from beyond 1000 and 4000 Hz. Therefore,
we can expectthat the higherfrequencycomponents the
100 Hz square  wavewill be relativelynormal in amplitude
and phase but that the lower frequencycomponents this
same square wave will be strongly modified by the poor
low-frequency response this amplifier.SeeFig. 46A.
   If the combinationof elementsin this amplifierwere
such as to only depress low frequencycomponents
                      the                          in
the squarewave, a curve similar to Fig. 47 would be
obtained. However, reduction in amplitude to a com-
ponent, as alreadynoted, is usually caused a reactive                                 Fig 47. Reduction of square wave fundamental
element,causing, turn, a phaseshift of the component,
                 in                                                                           frequencycomponentin a tuned circuit.

                                                         producin$ the strong tilt of Fig. 46A. Fig. 48 revealsa
                                                         graphical development a similarlytilted square
                                                                                of                      wave.The
                                                         tilt is seen to be causedby the strong influence of the
                                                         phase-shifted  3rd harmonic. It also becomesevident that
                                                         very slight shifts in phaseare quickly shown up by tilt in
                                                         the square wave.
                                                            Fig. 49 indicatesthe tilt in squarewaveshape  produced
                                                         by a 10" phase shift of a low frequencyelementin a leading
                                                         direction, Fig. 50 indicates a 10o phase shift in a low
                                                         frequency component in a laggingdirection. The tilts are
                                                         opposite in the two casesbecauseof the difference in
                                                         polarity of the phase angle in the two casesas can be
                                                         checkedthroughalgebraic     addition of components.
                                                            Fig. 51 indicateslow frequencycomponentswhich have
                                                         been reducedin amplitudeand shifted in phase.It will be
                                                         noted that theseexamplesof low frequencydistortion are
                                                         characterized changein shapeof the flat top portion of
                                                         the square wave.
                                                            Fig. 468, previouslydiscussed, revealedhigh-frequency
 Fig.48. Squarewavetilt resultingfrom 3rd harmonic       overshoot produced by rising amplifier responseat the
         phaseshift.                                     higher frequencies.It should again be noted that this
                                                         overshoot makes itself evident at the top of the leading
                                                         edge of the squarewave.This characteristic relationshipis
                                                         explained by rememberingthat in a normal well-shaped
                                                         squarewave,the sharpriseof the leadingedgeis createdby
                                                         the summationof a practicallyinfinite number of harmonic
                                                         components. If an abnormal rise in amplifier response
                                                         occursat high frequencies, high frequencycomponents
                                                         in the squarewave will be amplified disproportionately
                                                         greater than other componentscreatinga higher algebraic
                                                         sum alongthe leadingedge.

     Fil A)T tr PHASE

     Fig.49. Tilt resulting from phase shift of funda-
             mental frequencyin a leodingdirection.
                                                            Fig. 51. Inw frequency component loss and phase


 Fig. 50. Tilt resulting from a phase shift of funda-
                                                           Fig. 52. Effect of high-frequency boost and poor
          mental frequencyin a laggingdirection.

   Fig. 52 indicateshigh frequency boost in an amplifier
accompanied a lightly damped "shock" transient.The
sinusoidaltype of diminishingoscillationalong the top of
the square wave indicates a transient oscillation in ^
relativelyhigh "Q" network in the amplifiercircuit. In this
case,the sudden transition in the squarewave potential
from a sharplyrising,relativelyhigh frequencyvoltage,to a
level valueof low frequencyvoltage,supplies energyfor
oscillationin the resonantnetwork. If this network in the
amplifier is reasonablyheavily damped,then a singlecycle
transient oscillationmay be produced as indicatedin Fig.
  Fig. 54 summarizesthe preceding explanationsand
serves a handy reference.

                                                                                Fig. 53. Effect of high-frequencyboost and good

    A.   Frequency distortion. (crmplitude     B.   Low  frequency   boost         (qccenlu-      C.   High frequency    loss-No    phcrse
         reduction ol low lrequenry   com-          oted Iundomentql).                                 shilt.
         ponent). No phose shilt.

    D.   Low   frequency   phose   shilt.      E.   Iow     lrequency    loss    ond   phose      F.   High lrequenry    loss qnd low   fre-
                                                     shilt.                                            quency phcse     shilt.

    G. High lrequency loss ond phose           H.   Domped     oscillotlon.                            Low frequency phose shilt (trqce
       shilt.                                                                                          thickend by hum-voltoge).

                            Fig. 54. Summaryof waveformanalysis squarewavetestingof amplifiers.

                                                                  CIRCUIT DESCRIPTION

    The block diagram,Fig. 55, outlinesthe circuit break-                               high which forward-biases  D106 and Dl07 and reverse-
 down of the oscilloscope.
                         Circuit detailsare obtainedby                                  biasesD105 and Dl08 prohibitingCH B signalfrom the
 reference the schematic
          to            diagram.                                                        main amplifier.For CH B, the reverse true. WhenA & B
                                                                                        is selected,
                                                                                                   both channels alternately
                                                                                                                are             switched ICl0l
 GENERAL                                                                                at a rate equal to the chopping oscillator frequency
   Basically, the oscilloscope consistsof two identical                                 (200kHz). For A + B and A           B, both channelsar-e
verticalpreamplifiers,eachhavingits own input attenuator                                simultaneouslyapplied to the main amplifier. When X-y
network. The outputs of the verticalpreamplifiers be
                                                  can                                   operation is selected, CH A is turned on and CH B is
switched,as desired, into the main verticalamplifier.The                                switchedto the horizontalamplifier.
type of switching of the CH A and CH B preamplifiers   is                               VERTICAL AMPLIFIER
determined by the position of the MODE switch and
MODE of OPERATION LOGIC. The main vertical                                                 The selected  signalfrom the preamplifiers then applied
amplifier feeds the VERTICAL OUTPUT AMPLIFIER,                                          to the vertical amplifier which consists Q I 23, Ql24 and
which drives verticaldeflection
            the                  platesof the CRT.                                      IC103- The signal level is increased drive the output
   Horizontal deflection is provided by the horizontal
amplifier. Drive to the horizontal amplifier is furnishedby                                The output amplifier consists transistors
                                                                                                                         of           Q301 thru
calibratedsweepspeed   circuitsor by the signalfrom the CH                              Q306 where the signalis amplifiedto the levelsrequiredto
B preamplifier when X-Y operation selected.
                                    is                                                  drivethe verticaldeflectionplatesof the CRT.
   All supply voltagesare fully regulatedand a DC-to-DC                                 TRIGGER CIRCUIT
converterprovides regulated
                  a           2kV accelerating
the CRT.                                                                                _ f!. triggersource,  either CH A or CH B, is selected   by
                                                                                        SW20l. SelectingCH A as the source enablestrigger
VERTICAL PREAMPLIFIERS                                                                  ampl i fi er^Ql 19 and Ql 20 and C H B enablest r igger
                                                                                        amplifierQl21 and Ql22.The triggeramplifierselected       is
   ChannelA and Channel preamplifiers
                          B             containidentical                                fed thru transistor switch Q219. Q2l9 is on in all positions
circuitryand circuit operation the same both.
                              is       for                                              of the SWEEP    TIME/CM switchexceptCH B.
    The vertical attenuator has two sections.The first
                                                                                        SYNC AMPLIFIER AND INVERTER
se c t ion of t he at t e n u a to rp ro v i d e sra ti o s o f l :1, l 0: l ,
1 0 0 : , 1 0 0 0 : 1 .T h e s e c o n d e c t i o n r o v i d e s a t i o s f 2 : l
      l                                s            p            r          o               Transistors
                                                                                                      Q201, Q202,Q203,and e204 areconnected
a n d 5: 1. T he c om b i n e de ffe c t o f th e tw o s e c ti onss to       i         as a differential amplifier. The trigger signalis applied to
providethe verticalattenuator            ratiosin a l-2-5 sequence.                     emitter follower Q201 and routed to the baseof-e202 or
                                                                                        q?gi _depending    upon the position of the SyNC switch,
      The vertical preamplifierconsistsof FET input tran-                               SW202,* or - respectively.    Emitter follower e2O4 addsa
 s i s t o r s 1 0 2 a n d Q l 0 3 a n d t r a n s i s t o rQ 1 0 4 t h r u Q 1 0 9 .
             Q                                              s                           DC level to the tligg_ersignaldepending   upon the position
 FET' s Q 102 and Ql 0 3 fo rm a b a l a n c e dd i fferenti al                         of the TRIGGER LEVEL control.
 amplifier pair with output signalsof opposite polarity.
                                                                                           When TV+ 61 TV- is selected,      the output of Q203 is
 VR 101 is t he f r on t p a n e lD C b a l a n c e o n tro l a n d V R l 12
                                                         c                              routed to the SYNC SEPARATOR circuii consistingof
 a n i nt er nalbalance o n tro l .T h e o u tp u t o f Ql 0 2 a nd Q103
 i s appliedt o em it t e rfo l l o w e rs 1 0 4 a n dQ 1 0 5 w h i chl ow er           Q205 and Q206. Q205 is biased     near cutoff. e205 is held
                                          Q                                             cutoff by_ the negative voltage developedacross e205
 the output impedance drive conventional
                                to                              amplifierstage          corresponding an_average
                                                                                                       to               value of the input signal.
 Q l 0 6 a n d Q 1 0 7 . V R 1 0 5 a n d V R l 0 6 a r eb a l a n c e o t s f o r
                                                                         p              Positive-goingpulsesdrive Q205 out of cutoff. ihe outout
 th e llZ and ll5 a tte n u a to rp o s i ti o n s . h e V AR IA B LE
                                                            T                           of. Q205 corresponds the sync tips of the compoiite
 co n t r ol adjus t s he g a i n o f Ql b 6 a n d Q 1 0 7 w h i l e V R 101
                       t                                                                video signal.
 provides a DC component to move the trace vertically
 acrossthe screen.         Amplifier gain is adjusted VRl07 in   by                        Whenin TVV positionsof time baseswitch(.lmS to .5
'th e em it t er c ir c ui t o f                                                        SEC), capacitorC207 is switchedin by Q206 to filter out
                                   Q 1 0 8 a n d Ql 0 9 to p ro vi de the
 correct deflection factor for accuratevoltase measure-                                 the horizontal syncpulses.
 me n t s .
                                                                                           The triggersignalpassesthru emitterfollowere207 and
   The triggeramplifierQ I l9 and Q 120 amplifies signal
                                                the                                     the SCHMITTTRIGGER circuit consisting two gates
                                                                                                                                  of        of
a the emitter of Q 108 and Q 109 and provides portion of
                                              a                                         IC20I. The output pulses from lC20I ptN g clock the
tne signal the triggercircuits.
          to                                                                            SWEEP  CONTROL flip-flop 1C202. the negative
                                                                                                                         On             edgeof
                                                                                        the clock waveform,the Q output goeslow, turninf off
   The only differencebetween CH A and CH B pre-
amplifiers that the MODE switch reverses polarity of
          is                            the                                             Q213 to initiateto sweep.
the CH B signal
              when in the A-B position.                                                    Transistors Q216 and Q2l6 and the timing capacitors
                                                                                        and resistorsselected the SWEEP
                                                                                                              by          TIME/CM iwltch form
MODE LOGIC                                                                              a MILLER INTEGRATING circuit to providea linear ramp
                                                                                        voltage.The sweepramp from the collectorof ezIj is feb
    T he m odeof ope ra ti o n H A, C H B , A & B, A + B , A -
                                      (C                                                to the RS flip-flop consisting two gates
                                                                                                                     of         from IC201 thru
B ) i s c o n t r o l l e d y l C 1 0 l a n d I C 1 0 2a n d d i o d e s 1 0 l -
                          b                                            D                transistor
                                                                                                 Q211 andQ212.
D l 0 8 in eac hof t he c h a n n ep re a mp l i fi e rs .
                                                                                           As soon as the Q output of'lC2O2goeslow, the resetof
    WhenCH A is selected, output of IC 102 Pin 3 is low,
which reverse-biases
                       D102 and Dl03 and forward-biases
                                                                                        1C202is held low by Q21I to excludeany new clock pulses        U
                                                                                        until the sweepramp is terminated.Transistor
                                                                                                                                   e2l2 turns
D l 0 l and D104, al l o w i n gth e C H A s i g n a li n to the mai n                  on and setspin 13 of 1C202LOW which turnse213 on and
verticalamplifier.At the sametime ICl02 Pin 11 output is                                terminates sweep.


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   TransistorsQ208, Q209, and Q2l0 form the AUTO                           CH A AND CH B DC BALANCE
TRIGGER SENSEswitch. When the TRIG LEVEL control                                                                        trace( CH A or
                                                                            l . A dj ust control sto obtai na hori zontal
is adjustedso that the slopeis not triggered,transistorQ8                      cH B).
and Q9 produce pulses which keep Q2tO ON. The on
condition is applied to the RESET of lC2O2.A low on the                     2. A dj ustC H A or C H B P OS ITIONcontrolto cent ert he
reset of 1C202 allows a sweep to recirculate at a rate                         traceverticallyon the CRT.
determinedby the r.esistor   and capacitor selectedby the                   3. R otate the V A R IA B LE control from maxi mumCCW
TIME/CM switch.                                                                to maximumCW while observing trace.

   The sweep      ramp from the collectorof Q217 is appliedto               4. l f the trace movesverti cal l ymore than 5m m while
the input of the horizontal amplifier consisting Q218,                         performi ng TE P3, adj ustthe C H A or C H B DC BAL
Q 2 2 0 , Q 2 2 r- Q 2 2 5 .                                                   (front panel screwdriveradjustment) so that the
                                                                               verti calmovement the tracedoesnot exceed m
                                                                                                    of                        5m
   When in the CH B position of SWEEP       TIME/CM switch,                    while performing  STEP3.
mode, transistor Q2tg is turned off thru IC2O3and the CH'
B signal is applied to Q220 and to the horizontal amplifier.               I 12& I /5 ATTENUATOR BALANCE
Thetutput bi transistors     Q224 and Q225 is applied-tothe
horizontaldeflectionplatesof the CRT.                                       l . P osi ti on  traceto verti cal        centerof screen H A or CH C
                                                                                B , w i th V A TTE N U A TORi n .01 V /C U and input at
           CALIBRATION ADJUSTMENTS                                          2 . S w i t c h t o . 0 1 V / C M a n d a d j u s tV R l 0 5 ( C H A ) o r
                                                                                V R l 0 8 ( C H B ) u n t i l t r a c e s a t v e r t i c ac e n t e r .
                                                                                                                       i                   l
   The calibration adjustmentsoutlined here are those
which can be performedwith a minimum of specialized  test                   3 . S w i t c h t o , 0 5 V / C M a n d a d j u s tV R l 0 6 ( C H A ) o r
equipment. Additional internal adjustmentsof frequency                                                                                      l
                                                                                V R l 0 9 ( C H B ) u n t t l t r a c e s a t v e r t i c ac e n t e r .
compensation  and horizontal sweeplinearity shouldnot be
attempted without complete service information and
specified test equipment. Requestsfor complete service
                                shouldbe addressed
information for this oscilloscope                 to:                      VERTICAL GAIN ADJUSTMENT
                                                                                                     shouldbe attemptedonly if a
                                                                             The following adjustments
                   Seraice Departrnent                                     square wave generatorwith l% or better amplitude ac-
               B & K-Precision Product Group                               curacyis available.
               DYNASCAN CORPORATION                                          Procedure:
                 2815 West lrving Park Road                                 l. Set CH A and CH B VOLTS/CM switches      to.0IV/CM
                  Chicago, Illinois 60618                                       and set CH A and CH B VARIABLE controls to CAL
                                                                               (fully clockwise).
                                                                            2. Apply 1 kHz squarewave of 50 mV peak-to-peak    into
   lnt er nal adjustm e n ts u tl i n e d i n th e c a l i b rati on
                           o                                        pro-
                                                                                CH A input connector.Set mode switch to CH A.
ce dur e anbe loc a te d y re fe re n c to F i g .5 6 a n d 57.
        c              b                  e
                                                                            3. Adjust VRl07 for exactly 5 CM of deflectionon CRT.
HOUSING REMOVAL                                                             4. Repeatsteps2 and 3 for CH B and adjustVRI l0 for 5
                                                                               CM deflection.
 1. Remove6 screws,2 on left side, 2 on right side,and 2
    on top.                                                                HORIZONTAL PO$TION ADJUSTMENT
                                                                            l. Set <> POSITIONcontrol mechanical
                                                                            2. Set SWEEPTIME/CM switch to EXT.
 1. Removehousingfrom scope.
                                                                            3. Adjust VR206 so that the spot on the scope is
                        plug (seeFig. 58).
 2. Removevoltageselector                                                      horizontally centered CRT.
    3. Rotate plug l80o and re-insert                                                   <> POSITIONcontrol full CW and CCW.The
                                                                            4. Turn the
 4. Replace0.7A fuse with 0.3A fuse.                                           amount of deflection in both directions should be a
 5. Replacehousing.                                                            minimum of 4 CM.

 l. Grasp bezel with both handsat top and bottom. Pull
    bezel uniformly forward to unlock mounting legsfrom
    front panel. Caution should be used to keep bezel
    parallel to front panel when removing, avoid break-
    ageof mounting legs.

 2. Lift off graticulefrom bezel.

 3. Reinsertgraticuleon bezel and snap bezel into front
    panelmounting holes.

                                                                          @ u ^ 1 1 4 ,c R T c E N TA D J .

     VR11O                                                                            ( :o
                                                                                      \ /
    GAINADJ.                                                                                      GAIN ADJ.
                                                                                      rP l o2
            @                                                                                          @

                                             DC BAL.ADJ.
            @    HrGH                                                                        HrcH @
        TC114FREO                                                                            F R E O T C 1 13
             ADJ.                                                                            ADJ.


                                                                    @ tJot 6
                                                                   TC103             rtr os

                                                               TC104 TC102           TCl06

                                           F R O N T P A N E L ( B A C KV I E W )

                          Fig. 56. Calibration

                                      @                                                               vR 212
                                     vR 2o4

PANEL   i                                  @
                                         vR21o                      @
                                                                   r YJ
                                                         P o s r ro Nh
                                                            ADJ-                   @     @
                                                                                  VR2O8 VR2O9

                         Fig. 57. Calibrationdiagram,

                                                     POWER UPPLY OARD

                                                                                                     VR 3O5

     R O T A T E L U GT O

             240 VAC

             12 0 V A C

                                   F U S E o . 7A - 1 2 0 V A C
                                           0.3A- 240 VAC

                                                                  T C 3 0 1- M I D F R E O U N C Y
                                                                  VR 305-HIGH FREOUENCY
                                                                  V R 3 0 6 - 1 9 K VA D J
                                                                  V R 3 O 7- I N T E N I T YA D J
                                                                  VR 3OB-Y DEFLECTION
                                                                  V R 3 O 9 - 19 5 V A D J .

                            Fig. 58. Calibration diagram,power supply board.


l. Refer to the MAINTENANCE sectionof your B & K-Precision
   adjustments that may be applicable.

2. Defective parts removed from units which are within the One Year Limited Warrantv
   period.should be sent PREPAID to the ServiceDepartmentlisted below. Be sure to
   state the model and serialnumber of the unit from which the parts were removedand
   date the unit was purchased. Theseparts will be exchanged no charge,under the
   termsof the Warranty.

3. If the above-mentioned   procedures not correct the problem you are experiencing
   with your unit, pack it securely(preferablyin the original carton or double-packed).
   Enclosea letter describing problem and includeyour nameand address.
                              the                                            Deliverto,
   or ship PREPAID (UPS preferred) to the nearestB & K-Precision      authorizedservice
   agency (seelist enclosedwith unit).

If your list of authorized B & K-Precision  serviceagencies been misplaced,
                                                          has             contact
your local distributor for the nameof your nearestservice
                                                        agency, write to:

                                Service Deportment
                           B & K-Precision ProductGroup
                           DYNASCAN CORPORATION
                            2815 WestIrving Park Road
                              Chicago,Illinois 60618

                               ONE YEAR LIMITED WARRANTY
            DYNASCAN warrantsthat each product manufactured it will be free from defectsin
     material and workmanshipunder conditions of normal use and-service a p_eriod one (l)
                                                                             for         of
     year from the date of puichasefrom an authorizedDYNASCAN distributor. DYNASCAN will,.
     it its option, repair of replaceany product or component not- conforming with- the foregoing
     warranty and which is returned,traniportation prepaid,to our factory or our authorizedservice
     contracior. DYNASCAN shall not                  be linble for any damages,consequentialor
     otherwise.DYNASCAN makesno other expresswarranties.          Any implied vwrranties(including
     any worranty of merchantability) ore limiied in duration to (1) one year-fro.m the date of
     pirchase. This ivarranty does not apply to (i) damageresulting.from unauthorizedalterations
     and repairs,misuse,negligencyor aiCident; or (ii) damage   resultingtq1-qqp^tgper installation,
     conneition' or adjustment otherwise than in accordancewith DYNASCAN's authorized
     Instruction Manuai. This warranty is void if the serial number has been altered, defaced or
     removed. DYNASCAN reservesthe right to discontinue any model at any time or change
     specificationsor desiAnwithout notice-and without incurring any obligation. To registerthis
     warranty,t}e encloseiiDYNASCAN warranty registrationcard shouldbe completedand mailed
     to DYNASCAN CORP., 6460 W. Cortland Street,Chicago,Illinois 60635, within ten (10) days
     after date of purchase.

                                                                           @ 7 4 5 2 p R I N T E D N J A p A N B 5 o - 2 8 2 3 - o o( c )




        :   J




                6460 W. Cortlond Street
                Chicogo, lllinois 60635


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