Automatic Output Leveling; Adjustment; Modulation Meter Calibration Test; Pattern On 140 Oscilloscope At 50% Modulation - HP 608E Operating And Service Manual

Section V
Model 60BE!F
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140AlI4ZQ;\/I4QLA
OSCILLOSCOPE
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c. Adjust line voltage to 115 (or 230) volts. Adjust
RI06 for zero indication on PERCENT MODULATION
meter.
5-37. CALIBRATION OF PERCENT MODULATION
METER.
5-38. Recalibration of the PERCENT MODULATION
meter may
be
necessary following a repair of the
modulation measuring circuits (VI8-V21) or after
replacement of the meter itself.
NOTE
Be
sure the mechanical and electrical
zero is adjusted properly; re fe r to
paragraph 5-34.
Figure 5-14. Modulation Meter Calibration
Test Setup
a. Connect 608EjF and oscilloscope as shown in
Figure 5-14.
b. Set the MODUALTION selector to CWo
FREQUENCY RANGE . . . . . . . . . • • . . A band
l\'1EGACYCLES dial .••.•••.•••..• 10
MHz
MOD. SELECTOR. • • . . • • . . . . . • .. 1000'"
AMP. TRIMMER ... Adjust for maximum output
RF OUTPUT••.. ATTENUATOR CALIBRATED
MODULATION . . . . . . . . . . . . . . . • Fully CCW
c. Set the 140/1420/1402 oscilloscope as follows:
a. Return the MODULATION control to a meter
reading of 50%.
b. Turn the MO@. SELECTOR switch to 400'\,.
Meter should read
"±5%
of that obtained in step a.
5-41. 'AUTOMATIC OUTPUT LEVELING
ADJUSTMENT.
a. COIUlect dc voltmeter (50-volt range) to junction
of CR26-R235 (Figure 5-16) and ground.
b. Set RF OUTPUT control fully counterclockwise
and MODULATION selector to CWo
)
VERT. SENS •..•... . .. 0.2 V /cm
HOR. SWEEP TIME. . • . . • • . . •. 0.2 ms/cm
TRIGGER SOURCE •.••..•..
+
!NT or - !NT
d. Adjust vertical position to place pattern at
center of screen.
e. Set MODULATION selector to 1000< Adjust
608E/F Attenuator for
a
4 cm pattern on screen.
c. Adjust R204 (Figure 5-14) to point where dc
voltmeter shows no f u rt he r voltage increase witi,l
adjustment of R204.
d. DC voltmeter should indicate greater than
30 volts.
e. Set MODULATION selector
to
400 "", 1000 "",
and AM position; dc voltmeter should indicate greater
than 30 volts at each switch position.
5-39. ADJUSTMENTS.
a. Increase MODULATION control until sine wave
pattern appears on oscilloscope. Adjust trigger level
for stable pattern.
f.
Set MODULATION selector to PULSE/SET RF
OUT PUT; vol
t
met e r should indicate greater than
14 volts.
b. Increase MODULATION control until peak-to-
peak pattern is 6 cm high, as shown
in
Figure 5-15.
Adjust R104 (METER CAL on rear panel) for a read-
ing of 50% on the PERCENT MODULATION meter.
c. Increase MODULATION control until the peak-
to-peak pattern is 8 cm high. Adjust trigger level as
necessary to keep s tab
I
e pattern. The PERCENT
MODULATION meter should read approximately 100%.
5-40. This c he c k will determine if the modulation
meter circuitry (VIB-V21) is frequency sensitive. It
will also check the relative output of the Modulation
Oscillator (V2).
5-14
Figure 5-15. Pattern on 140 Oscilloscope
at 50% Modulation
)