Electronics > Repair

Fluke 343A repair

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Rax:
I've not yet taken any measurements to start diagnosing this, but one thing I'm sure is this is a new, or possibly intermittent issue. Differently put, the power supply work was necessary, and it brought TP4 and TP5 within spec.

But there's more work ahead.

bastl_r:
Hi
I am also very interested in the progress of the repair as I will soon be getting a 343 which is supposed to work.
If it works already I can also make comparative measurements for you.

Regards

70bytes:
Hi,
my 343A stopped working after running it for 5 hours. The limit LED went on and the needle wanted to go far below 0V.
After investigating the problem i found that the 63mA fuse has blown.  I replaced the fuse with a new one and turned it on. The limit LED turned off and immediate turned on again. This time the needle wanted to go to the other site over its max limit. I measured 200V+ at the outputs in the 10V range.
The cause of this problem in my unit was a dirty standby/On switch. After cleaning the switch the problem was solved.

I few moths ago i had a problem that it wouldn't tun on. No relay clicking sound. The cause of this problem was diode CR31.

Regards,
Maurice

Rax:

--- Quote from: 70bytes on June 14, 2024, 10:03:11 am ---I measured 200V+ at the outputs in the 10V range.
The cause of this problem in my unit was a dirty standby/On switch. After cleaning the switch the problem was solved.

Regards,
Maurice

--- End quote ---

Thank you, Maurice. This may be exactly what I have here.

One question I have is how does the cover masking the switch come off, if you recall. There's of course two, one on top, one on the bottom. They're attached with two screws, but they won't come off if I remove the screws. Does this need the handles to also come off, or something like that? The manual seems to indicate they should just come right off.

70bytes:
For the top one you need to pull op from the middle. It will fold a bit and come loose. It has slots on the sides.
The bottom one i think is the same.

I have a very early one. Serial# 183
I don't know if later units are build the same.

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