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Old Fluke Multimeters

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retiredcaps:

--- Quote from: imaradiostar on April 28, 2019, 01:05:38 am ---Is it fair to assume there is still junk on the board or MAC somewhere causing the incorrect scaling?

--- End quote ---
It might take several applications of IPA and cleaning? See

http://mrmodemhead.com/blog/fluke-8060a-repair/

imaradiostar:
You're probably right. It's been a while since I read that blog post. Even though the meter was supposedly refurbished, it's silly not to dig in a clean it again, and possibly swap the MAC with a meter that functions correctly to see if the problem follows.

Knowing myself and the likelyhood that any older 8060a would have bad caps and related problems, I sortof regret buying one that's "refurbished" for decent money when I already have the charge pump and machine pin sockets on hand, and the caps are cheap. I have no doubt that I can put it right, only I have little time right now to do it.

I have three 8050a's, an 8060a, and a modern Owon B41t+ apart on my bench, and I just purchased a used Fluke 187 for use at work without knowing if it functions correctly. I have the IBM 8060a and an additional 8050a apart at work. Too many projects! I enjoy the distraction, though. Somehow messing with multimeters scratches some sort of OCD itch and I find it satisfying.

oh yeah, I have an HP 3478a apart, too. Needs a power transformer. Neat meter, though. Oh, and an 8920a that reads off by about 20%. Found some caps with high ESR, but no smoking gun yet.

Yeah, it's a sickness. I think there is a thread for that.

Jamie

GregDunn:
The "addiction" continues...  I found a nice clean 8600A at the Dayton hamfest yesterday for $20.  Using my 10V standard, MC-7 precision resistor set and HP 6920B it measures very close on all functions and ranges.  I always take these apart to make sure there's nothing questionable going on inside, and this time I see that a previous owner replaced some components (U4-5 seem to have been the target) because there is a lot of flux residue. 

U4 is supposed to be a LH0042C so I could check to see whether the sub is appropriate, but U5 is listed only as Fluke PN 385450 which is generally referenced to an AD40323.  Both are of course selected for (I assume) leakage or offset; but right now U4 is an AD40291 and U5 is an AD40420 and I can't find any data for any of them so far.

I suppose I shouldn't worry about it - the meter is rock stable after about 5 minutes of warmup and seems to be well within spec.  But I'd really rather have some more info because if one of these goes bad on another meter... well.

bob91343:
Do you want to foist that 3478A on someone who might try to repair it?  That would be a fun project for me.

imaradiostar:
Sorry, it's a company asset, can't sell it!

JT

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