Electronics > Repair
Keithley 2002 repair help
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TheSteve:
Sounds like you're making great progress.
FYI I've had a power supply from an HP network analyzer before with caps that leaked. No amount of alcohol would remove the contamination film on the PCB. I couldn't see the film, but an ohm meter could measure it. I had to scrub with water etc and then finish with lots of alcohol to bring it back to life. And the power supply was likely nowhere near as sensitive to contamination etc compared to your K2002.
Kleinstein:
The critical of the max326 used in the ohms section is U223 according to the plans (TiNs and the last one below) shown.

If even the rather large amount of leakage in the amps range seems to have been due to leakage, chances are the the ohms part leakage is also due to contamination.  So my suggestion would be a little more cleaning, especially around U223 and the 75 K ref resistors. Even if the first try on cleaning would not solve the problem, any significant change would give an indication that contamination is the culprit.
nikonoid:
Thank you very much, Guys.

Today I did a bit of DI cleaning followed by IPA and now it is time for some baking  8)  at 130F   (see attachment)

Should 2 hours be enough?


floobydust:
That's great news. It was a lot of work.
After an IPA wash, a hour in heat should be fine. It's just the water (if not 100% IPA) needs time to evaporate underneath IC's.

I've never seen leakage on a PCB like you were observing.
Unless they used the incorrect flux/wash, or creep corrosion is occurring. Not to be confused with tin whiskers.
Creep corrosion is usually blackened copper in dendrite-like patterns.


I have Keithley 2001,2001 service manuals but they contain no schematics, just long flow chart of parts to replace, kind of gross.
Zucca:

--- Quote from: floobydust on October 11, 2017, 03:58:38 am ---I have Keithley 2001,2001 service manuals but they contain no schematics, just long flow chart of parts to replace, kind of gross.

--- End quote ---

Here the schematics K2001 and tons of info about the K2001

https://xdevs.com/fix/kei2001/#fix_2001

Back to the K2002 repair, nikonoid go on like this... you will win for sure!
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