Electronics > Repair
Keithley 2002 repair help
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Kleinstein:
If the burnt part is only on one side of the board, one may not need a full hole in this area. If can be enough to remove the two burned layers for the one side. One could use something like a Dremel tool, or just scraping by hand with a knife.

It looks like there are 3 lines from below in the burned area, and nothing to the right. Likely there are good quality pictures on the xdevs site so one could get an idea where those lines are heading.
TiN:
Best pic I had of that area is this one. Didn't take more photos of analog section, as there was nothing wrong on my second 2002 in there.

Also suggest not to take shortcuts and desolder all SMD parts in affected by electrolyte leak area (and replace cheap ones with brand new stuff), instead of thinking that little IPA and brush is enough.
nikonoid:
This is a great photo. Thank you, TiN. I can clearly see here layer 2 and what connects to what. Big help.


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nikonoid:
Today I found a second contributing factor to condition of the meter. Someone installed a 2 amp mains fuse instead of 1/2 amp. So one short happened due to electrolyte leak, it kept burning the board.

I started cleanup of the PCB burn. Made a decision against using dremel. I decided that any power tool throwing tiny conductive particles all over analog board is not a good thing  >:(. Arming myself with a wooden toothpick and 40x microscope, I removed as much of charred PCB as possible, periodically cleaning fine debris with IPA and Q-tips. After that came 1/16 drill bit in a Pin Vise (driven by hand) where some damage was drilled through and some scraped. Then I finished with an exacto knife. I am still debating with myself if I will remove more material.

I am potentially looking at making 5-7 bodge connections using thin transformer wire. Many of them will be soldered to tiny vias connecting 2nd and 3rd layers, showing on the surface only as a tiny dot. Is this an Ok thing to do or should I opt for much longer budge wire so I can solder it to more reliable spots?

Looking at the board under microscope proved that you guys are right again. I can clearly see electrolyte damage on some chips and traces. I will have to remove at least 7 ICs. Last time when I decided to cut legs of a microchip it worked,  but less than perfectly. I am considering a using a soldering fan, covering nearby areas with either kapton film or aluminum foil for heat protection. Are there reasons not to do this and use some other technique?



Meanwhile here is more high res photos. This is the initial stage:


And this is after removing leaked capacitors and rectifier and a bit of cleaning:


I am still working on 4 layer PCB diagram on this section. I will post it soon. To create this diagram I took few photos on the PCB with light shining through it to help me see internal traces.


TheSteve:
I wouldn't be cutting the legs of SOIC packages to remove them - IMHO that is a pretty bad way to do it. I much prefer to put a bunch of solder down the pins on one side, then lift it a little with a sharp knife. Then add some solder to the other side, grab the part with some tweezers and touch both sides back and forth and it should lift right off. With a little experience it is very quick. You can use the soldering iron to wick away most of the left over solder and then finish the cleaning with some wick, then alcohol.
Keithley PCB's aren't top quality but they aren't terrible either.
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