175A - HP Archive

Section V
Paragraphs 5-47 to 5-50
Figure 5-6. Attenuator Compensation
(Top: undercompensated, Middle: compensated,
Bottom: overcompensated)
s. Disconnect 600-ohm Square- Wave Generator
output from foam-covered wire and connect Generator
to HORIZ INPUT. Adjust output amplitude for 8 cm
deflection and frequency to 4 kc.
t. Adjust Attenuator Compensation C203 for round
dots with no tails (see figure 5-6).
u. Disconnect Square- Wave Generator and jumper
from vertical INPUT and sweep-generator printed-
circuit board. Connect foam-covered wire to sweep-
generator printed-circuit board.
5-47. SWEEP GENERATOR.
5-48. Refer to figure 5-3 for locationof adjustments.
5-49. PRESET.
a. Set:
HORIZONTAL DISPLAY ......... XI
SWEEP TIME ......... lOpSEC/CM
b. Connect DC Voltmeter to pin 3 of V109. This
voltage will be approximately -40 volts.
c. Rotate SWEEP MODE slowly clockwise while
watching Voltmeter. Meter pointer will jump when
sweep generator free runs.
. d. Note voltage at which sweep generator free runs
(maximum negative reading obtained on Voltmeter).
e. Set:
SWEEP MODE. ........... PRESET
f. Adjust Preset Adj R170 for meter reading of
2.5 volts less negative than voltage noted in step d.
5-10
g. Disconnect Voltmeter.
Model 175A
5-50. TRIGGER SENSITIVITY AND SYMMETRY.
a. Set:
SWEEP MODE ........... PRESET
TRIGGER SLOPE ............. (-)
TRIGGER SOURCE ......... EXT AC
HORIZONTAL DISPLAY ......... X1
SWEEP TIME. ......... 1MSEC/CM
Vertical SENSITIVITY. .. 0.05 VOLT/CM
Vertical AC-DC ............. AC
b. Connect Model 10003A (AC-21M) Probe from
vertical INPUT to case of tunnel diode CR102 on
sweep-generator circuit board (see figure 5-3).
CAUTION: +110 VOLTS present at this point.
c. Connect Calibration Generator to TRIG INPUT
and adjust output for 0.05 volt rms.
d. Mechanically center Trigger Symmetry R116,
and turn Trigger Sensitivity R120 fully clockwise.
e. Rotate TRIGGER LEVEL to obtain a free run-
ning display approximately 0.5 volt in amplitude (see
figure 5-7).
Figure 5-7. Trigger Sensitivity
(Top: Synchronized, Bottom: Free Running)
f. Using TRIGGER LEVEL to maintain a presen-
tation adjust Trigger Sensitivity R120 counterclock-
wise until a stable, synchronized, symmetrical
square wave approximately 0.35 volt in amplitude is
obtained (see figure 5-7).
g. Set Calibration Generator output to 0.03 volt rms.
h. The trigger circuit should not trigger solidly.
Counterclockwise adjustment of Trigger Sensitivity
RH0 may be necessary to prevent solid triggering.
Rotate TRIGGER LEVEL when checking for solid
triggering.
i. Set Calibration Generator output to 0.05 volt rms.
j. The trigger circuit should again trigger solidly.
Adjust TRIGGER LEVEL if necessary. Repeat steps
f, g, h, and i until circuit triggers solidly with a
0.05-volt rms input and does not trigger solidly with
a 0.03-volt rms input.
01526-1