[volt-nuts] Fluke 845A mystery
frank.stellmach at freenet.de
Sat Feb 4 16:28:18 UTC 2012
Following your description, any output deflection seems to load the
+/-15V supply abnormally.
After having a look at the buffer caps C117/118, I would suspect the
transistor pairs Q113/114, Q203/204, or Q111/112 for having a strong
mismatch of current gain, or a simple malfunction.
(For the refs.: I own the old schematics from the 60's only)
Btw.: As your unit is of younger vintage, does it still have the optical
choppers with neon bulbs, or has this been replaced by a MOSFET chopper,
as in the 332/335 calibrators?
If the latter is the case: Do you have a schematic and would it be
possible to get a copy, please?
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