HEWLETT PACKARD (HP) 150AR
Service Manual

Sect. IV Page 19

a vertical deflection sensitivity of 1 volt per centimeter.
7) Connect test oscilloscope probe to junction of R65 and a r m of S2 TRIGGER SLOPE switch (use ac coupling). This point can be identified as the connector approximatelymidway between tubes V9 and V17 to which a greenwire from the TRIGGERSLOPE switch is connected. If high frequency oscillations a r e present, rotate R66 maximum counterclockwise.

No. 15OA-65 E, L or LR only. See Figure 4-7B.
a. Connect a dc VTVN between ground and pin 2 of V10. The voltmeter indication will swing between approximately -40 and -15 volts.
b. Adjust R88 to obtain -15 volts a t the end of the sweep. Ifunable to setR88, rotate R135 until R88 may be s e t properly. 4) Connect the dc VTVM between ground and pin 8 of V15. The violet wire terminated above V15 connects to pin 8. 5) The voltmeter indication will rise and fall with the sweep. Adjust R122 or R135 (see Figure 4-7) until the end of the sweep occurs between -110 and -115 volts. 6) Set the SWEEP TIME/CM t o . 1MICROSECONDS, SWEEP VERNIER to CAL. and HORIZ. SENSITIVITY to X1. Connect the test oscilloscope to pin 8 of V15 through a low capacity probe andobserve the sweep waveform, Adjust C40 for maximum undistorted amplitude. Undesirable distortion will appear at the most negative point on the waveform.

8) Refer to Figures 4-7 and 4-8. Adjust potentiometer R66 and R72 for pips vertically spaced exactly 1 volt apart on the displayed sine wave. In addition, the pips must be exactly 0.5 volt above and below the center of the wave. The upper pip must be on the positive slope portion of the sine wave and the lower on the negative slope. These two controls interact but pip vertical separation is primarily controlled by R66 and vertical position of both pips by R72. Repeated adjustments of both controls may be required,

c.

ADJUST SWEEP PRESET

1) Disconnect any external vertical input to oscilloscope. Set SWEEP TIME/CM switch to .1 MILLIS E C ONDS and SWEEP MODE control maximum counterclockwise to PRESET. Set SYNC. selector to INT.

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Figure 4-8. Sync Trigger Hysterisis Limits
I pips a r e not visible, set R66 as far clockvcl-je as possible without introducing oscillation and -then

2) Connect thedcvoltmeter +tween ground (+) and pin 2 (-) of-V10. Slowly adjust R103 until the sweep generamr begins to free-run. The voltmeter indi-

cation will increase, as R103 is rotated, to a maximum and ,then suddenly drop, when the sweep generator begins to free-run. Repeat this several times and note the average maximum voltmeter indication. The exact value of this voltage is not critical and will vary with individual crhahcteristics of tubes V10 and V11.
3) -Se1-R1'03 tb give a voltmeter indication exactly 1.5 volts less negarive than,the maximumnoted before the sweep began to free--'run. For example: if the maximum voltage noted was -37 volts, R103 should be set for -35.5 Volts. . '>

slowly rotate R72 until the pips appear.

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B. ADJUST START-STOP TRIGGER AND SWEEP AMPLITUDE
1) With no inpyt-ts the oscilloscope, set the SYNC selector to EXT. AC.

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2) Set the SWEEP TJME/CM tp 2 and rotate SWEEP 'MODE maximum clockwise to FREE RUN. , .-- ,: ,. '
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SECONDSLCM * .-.. b.' ADJUST .SWEEP CALIBRATION - , - ,.\ C .
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3) This step is for Sweep Generator Assemblies

Physical- location of the variable capacitors for Sweep Calibraiioi has varied with production. Compare the configurations shown in Figure 4-9 to find