Section
VIII
Model 34S5A
SERVICE GROUP E
8
E-1.
AID
CONVERTOR AND INGUARD LOGIC
TROUBLESHOOTING.
8 E-2. AID Convertor Servicing ISchemetic 6, 7).
8-E-3. Before troubleshooting the A/D circuits make sure
the
outguard
section of the 3455A is
operating correctly. Use the half-splitting method of paragraph
8-1
9S.
The following procedures may
be used to check the correct
operation of the A/D circuits.
a. Turn the 3455A off. and
disconnect the AlOWI Inguard/Outguard Cable assembly from the
outguard connector (A1J7).
b.
Remove
the analog test jumper
(from
A10U27
pin
10),
and connect test point A10TP9
to
ground.
c.
Apply
-10
V dc to the input terminals of the 34SSA and turn the instrument on.
d.
With
an oscilloscope measure the waveform at AlOTPl. The
waveform
should look
like
top
waveform
in Figure 8-E-l.
e. The correct
waveform at TPl generally indicates correct A/D operation. If,
however,
the A/D
waveform is good and the A/D circuit is still
inoperative,
go to
paragraph
8-E-7
for troubleshooting.
Figure
8 E-1.
A/0
Waveforms.
8-68
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