Electronics > Repair
Keithley 2002 repair help
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nikonoid:
Another update on repair process. I removed all components affected by the spill. They were easy to identify under microscope. This is a full resolution image of the board after the cleanup. For general areas I used canned air with zero oils in it (MG Chemicals super duster 134). Areas with the spill damage were cleaned multiple times with 99% IPA. IPA was not able to remove all the board discoloration. Some corroded pads were scratched a bit with solder wick and re tinned.

I left some dirt around R319, as I was not comfortable desoldering these components, esspecialy precision resistance network. I might try to clean around them with IPA later.



Remarkably only 3 traces were compromised by the burn. Additionally several traces around C116 were eaten away completely.


I took several pictures of copper and component side of analog board. I used light painting technique described by TiN and lit the board from behind to see internal traces. Two images below had been aligned, and flipped in Photoshop to closely correspond to one another. This way you can see traces, including most internal traces, and switch from copper to component side without loosing what you are tracing, but just hiding/un hiding layers. Maybe these will be useful for someone.




Finally on following two images I colored traces important for my repair. Red is the Component layer, blue and yellow and following internal layers and yellow is the copper layer.



I already started repairs and faced few challenges. My original plan was to solder copper transformer wires to micro vias to fix broken connections. All of my attempts to solder to micro via failed. I even tried to excavate the via a bit by removing a bit of PCB material around it under microscope. So far around capacitor C116 I had to reconnect vias to traces missing .3mm to 1mm of copper. The only way I was able to reconnect them was by forming a "solder bridge" between them. Testing showed them electronically connected and mechanically sound. Any attempt to use copper wire for that failed. While solder bridge solution is far from ideal I would like to hear some opinions.

Any advice on how to solder to micro vias? If I cannot solder to micro vias, 3 traces that were broken will have to be repaired by wires stretching half the way though entire board. Thanks.
WastelandTek:
First things first; great work!  The effort you have put in really shows.

As far as getting the transformer wire to bond; what are you using for flux?  Are you able to tin the wire first?  It seems odd that it is refusing to bond.
TheSteve:
Is the solder not sticking to the via or the wire? The enamel on the wire can be a pain.

And I agree with WastelandTek - great work so far, I really appreciate the post detail. I have no doubt someone else will be helped by it in the future.
nikonoid:
I scraped and tinned the transformer wire first. I used Kester 951 low solids flux pen.
I used same flux on the via.

Via might be corroded with electrolyte or maybe it is just too small and surrounded by solder mask that repels solder. Maybe the gauge of the wire is too big for the via? I just know that I had been trying for a while without good results.
WastelandTek:
You might try some no-joke RA flux, I use MG chems 835, pretty aggressive stuff.

PM me your zip, if you're local I have a litre of it...lol
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