Electronics > Repair
Please help, FLUKE 8920A Multimeter Repair
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Harry_22:
Dear Daisizhou. With grounding the background noise has noticeably decreased.
It seems that your well-heated soldering iron scared off our malfunction and now it may not appear soon.
You can go another way. You remove C18 and measure its resistance with a multimeter. It is up to you.
daisizhou:
OK。I plan to do it in 2 steps.
The first step is to buy a brand new 50V 1UF tantalum capacitor.
The second step is waiting for transportation,Since shipping takes a few days until new capacitors are received, I perform one last test to see if the fault can be reproduced and measure the resistance of the old capacitors.

Because it won't be a waste of time
daisizhou:
Tested again today, the good news is that the fault reappeared, the bad news is that I haven't tested the heated C18 yet, the fault disappeared again, I took part of the video。
I seem to have discovered a pattern,That is, the longer the power outage lasts, the longer the failure will last.
It seems that it is not that the capacitance of C18 is reduced, but that there is a possibility of C18 leakage current.


Sometimes the fault of closing the shielding shell can be maintained forever,When you open the shielding cover or connect the TP1 test point, the fault will disappear automatically. It’s more serious on rainy days.Watch the video below.
daisizhou:
I received the 50V 1UF capacitor and tested it for LCR.
Next I am going to disassemble C18 and replace it with a new 50v 1UF one
daisizhou:
I replaced the C18 capacitor.
and measured the old C18 and it looked like it was normal
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