Electronics > Repair
Fluke 343A repair
<< < (3/12) > >>
Rax:
In undertaking the recapping job, a word of warning is paying attention to the conformal coating. Not a thick or really hard to pierce/melt polyurethane coating - I wore a mask half way through and had the door wide open for ventilation - but it can mess with the desoldering tips and require constant cleaning and retinning. I clogged one tip, which is very frustrating,  given the cost of a Pace tip.
Rax:
Well, I wasn't aware of this, but these "small current" fuses have not negligible resistance. So my continuity test was likely not a proper test. I got replacement fuses, and both the replacements and the original fuse measure around 80 ohms... So I guess my issue is not the HV fuse having gone open. Live and learn.

So I'm back to the drawing board and head scratching. I may decide to continue my recapping job - my money's still on caps having failed during my "bake out" ("-in...?") initial run - or just take a closer look at the SM and see what my next troubleshooting steps should be.
Rax:
I decided to start over more slowly and methodically. I've redone the 4-39 tests, and got slightly different results. One thing I did differently this time is to bridge the OUTPUT and SENSE terminals, and that answered one of my prior questions (see below).


* TP2: 2.78k
* TP3: 5.3k
* TP5: >160k
* TP6: 1.98k. Not compliant?
* TP7: 680k
* -SENSE: 57
The last on that list answered my own question: the OUTPUT-SENSE bridging is supposed to be in place for these tests. Hopefully, this helps others that may run into the same dilemma I did.
Rax:

--- Quote from: Rax on May 31, 2024, 12:22:13 am ---
* TP6: 1.98k. Not compliant?
--- End quote ---

The SM calls into question CR26, CR27 and lamps DS5, 6, or 7. But I diode-tested the CRs out of circuit and the DSs are lighting when switching voltage range. The resistance from TP6 to +SENSE doesn't change at all either when operating the range switch.
Rax:
I rechecked the voltages at the test points, and I'm not seeing any significant variations.

Due to the non-compliance of TP4 and TP5, I am becoming suspicious of SINK SUPPLY + CROWBAR DRIVER and maybe the HV POWER SUPPLY. I've diode-checked CR1, 2, 3, 4, 5, and they tested fine.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod