Procedures - HP 3400A Operating And Service Manual

OH
PASSES
Figure 5-6. Troubleshooting Tree
Figure 5-7. input to Demodulator
Cheek
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Procedure
Set the 3400A to the 1V range. Apply 1V 400Hz ac
signal to the input terminals. Measure the signa! at
junction of C413 and 415. The reading should be be-
tween 240mV and 280mvV RMS.
Measure the signal between TP2 and TP1 on the A6
assembly. The signal should look like the one in
Figure 5-7.
Troubleshoot and reparr oscillator circuitry.
Turn the 3400A off and piace the A6 board on an ex-
tender board {-hp- 5060-6038). Unsolder and litt one
end of R616 trom the board {the dc feedback is now
disconnected). Set the instrument to the 1V range and
apply a 1V, 400Hz RMS ac signal to the input terminals.
Using a Digital Multimeter (like the 3468A/B), measure
the voltage between TP3 and TP1 on the A6 assembly.
The voltage should be approximately 2mV to 2.5mV ac.
Check tor a defective TC401. TC401 may also be discon-
nected from the output of the video amplifier via
capacitors C413 and C415.
Turn the instrument off and replace and resolder
R616 on the A6 board. Make sure the 3400A is stit!
on the 1V range and the 1V, 400Hz signal is stil! applied.
Turn the instrument on and measure the voltage between
TP4 and TP1 on tne AG board. The voltage should ap-
proximately be -4V cc.
If the voltage ts positive, check for a shorted CR6O3. If
the voltage ts negative but other than -—4V, U602 or
TC401 may be cetective.
Check the voltage between TP5 and TP1 and make sure
itis ~.19V.
Troubleshoot the filter circuitry consisting of R617
through R619, and C606 through C608.
Check tne voitage between TP6 and TP1 and make sure
it is approximately — 1V.