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Old Fluke Multimeters

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e-doc:
Can you help me please to fix offset error on an old Fluke 8060A?

On shorted input the display shows following offsets:

--- Code: ---range     offset
200mVDC  -0.14
2VDC     -0.0002
20VDC    -0.18
200VDC   -0.14
1000VDC  -0.14

200mVAC   0.15
2VAC      0.0051
20VAC     0.14
200VAC    0.14
1000VAC   0.14

200Ohm   -0.14
2kOhm    -0.013
20kOhm   -0.11
200kOhm  -0.11
MOhm     -0.07

--- End code ---



I found a leaked electrolytic capacitor (C12, 10uF, 16V) and the socket of the MAC contaminated with electrolyte.
I replaced C12 and the socket with new ones, cleaned the area arround the MAC and C12 using brush and isopropyl.
I also cleaned the PCB around the input connectors with IPA, because the former owner of the DMM resoldered all the input bushings and left some flux residue.

Result: same as before... :-//
I also checked power supply voltage +5.2V, -5.1V, 3.15V, bandgap 1.24V - looking good so far.

lowimpedance:
Just a thought, what about the MAC chip itself needing a IPA clean if its original socket was contaminated!. (you did IPA the area where the leaking cap was too ?).

e-doc:

--- Quote ---what about the MAC chip itself needing a IPA clean if its original socket was contaminated!
--- End quote ---
The gold plated pins looked OK, no visable contamination at the MAC at all.
Only one contact spring of the socket was colored darker than the remaining ones.
Maybe I should bath the MAC completely (?). I just don't want to take it out of the socket, because it was tight to insert the gold plated precision socket.

--- Quote ---(you did IPA the area where the leaking cap was too ?).
--- End quote ---
Of course. I found some green "copper rust" at the PCB under the leaked cap.
After removing the dirt mechanically and by IPA, I resoldered the PCB tracks around the spot to remake their tin-coating. Then I IPA-brushed the whole area (MAC and C12) again.
After replacing the socket and C12 I IPA-brushed it twice.

krivx:
My 8060A's MAC needed a couple of IPA soak-and-drying runs before the residual readings decreased to zero.

e-doc:
Can I sink the whole PCB (including switches and buzzer) in IPA without damage?
What about the grease on the switch contacts?
I can use an ultrasonic bath too.

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