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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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