HP 3400A Operating And Service Manual page 30

Model 3400A
CHECK
@
Investigate
and V504.
check.
Figure 5-9 for waveform.
for details.
@
Investigate Q603 and associated circuit.
@
Increase the level
Vdc. Measure the ac signal at the base of Q60 1.
Refer to Figure 5-12 for waveform.
CHECK
@
Investigate Q60I and associated circuit.
@
Investigate V501. V502. C601. C602 and R601.
See Paragraph 5-39 for photochopper check.
Check chopper neon voltage.
for waveform. See check number
@
Measure the ac signal at the output of impedance
converter
should be approximately 0. 96 m V rms.
@
Measure the
A4 }X>sitive side of C402.
approximately 0. 96 m V rms.
@
Measure the ac signal at the base of Q404.
reading should be approximately 155 mV rms.
01768-3
Table 5-6. Troubleshooting Procedure (Cont'd)
PROCEDURE
'
Q604. C605. (and demodulator) . V503
See Paragl"aph 5-39 for photochopper
Check chopper neon voltage.
See check number
of
tbe inserted signal to +0.·2
Fignre 5-12. Base of Q601 (feedback loop open)
Table 5-6. Troubleshooting Procedure (Cont'd)
PROCEDURE
Refer to Figure 5-9
A2 of
(negative side C205).
ac
signal at the input to video amplifier
The reading should be
@
Refer to
PASSES:
FAILS:
BASE OF Q601
+ .
resistor to pin 1 3 on A6
Sweep
vertical
AC coupled
no probe required
@
for details.
PASSE S:
The reading
FAlLS:
PASSES:
FAlLS:
The
PASSES:
FAlLS:
ACTION
@ @
Proceed to
Proceed to 18
2Vslgnal through 499 k!1
= 5 rns/em
5 mY/em
=
ACTION
@
@
Proceed to
Proceed to 23
@
@
Proceed to
Proceed to
@ @
Proceed to
Proceed to 25
Section V
5-13