Keithley 1920 Instruction Manual page 22

Maintenance
Model 1920
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TABLE 3-6
Model 1920 Troubleshooting (cont.)
STEP
10
11
12
13
14
ITEM/COMPONENT
REQUIRED CONDITION
Select 2ov range
a,j apply 1OV AC at 1kHZ
Select 2oov ranye ard
apply 100 V AC at 1kHZ
Select 700V range ard
apply 350V AC at 1kHZ
Select AC + DC function
ard the 2V rarqe. Apply
1v DC
Select AC apply IV DC
KEIlAKKS
(virtual ground)
If display overranges
check (1406 an3 Q407
for gate drive ard
signal
If
display met-ranges
check Q404 ard Q405
for gate drive anl
signal
If display wet-ranges
check Q402 arrl Q403
for gate drive drd
signal
Check display for 1V
if not, check (1401 an3
K401
Oisplay approx. OV
if not, check Q401
K401, c401
NOTE
If the 1OOV 1OUkHz adjustment cannot be brought into specification,
check the spaciny between C4Ul and K403. If these components have
been bent toward or away from each other, C413 may not have adequate
calibration ranye. Moviny C401 and K403 closer toyether increases the
1OOkHz response on all ranges.
Check and adjust, if necessary.
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