[sdiy] de-potting

Mike Pepper profpep at hotmail.com
Mon Sep 20 16:06:06 CEST 2010


>
> > I did my Gentle Electric potted module with a hammer and
> > screwdriver. OTOH I was able to discern the circuit from the
> > exposed PCB and did not need to remove ~all~ the epoxy
> >
> > H^) harry
>
> That's an approach I've been considering with some potted modules I have
> here.
> If I just expose the PCB foil, identify every component leg, then isolate
> each leg by cutting tracks, a combination of LCR meter and Atlas component
> analyser might get me a good part of the way through RE-ing the ciruit
> before I need to uncover any component bodies.
> This approach does require a working circuit to be sacrificed.
>
I used a similar approach, but used  a small Dremel type grinder/burr to
examine the content of blown motocross bike ignition trigger modules years
ago. A dust mask is essential! First unit I put on a linisher and ground
down until I could see the beginnings of the solder joints, then picked away
the remaining epoxy with a hard point tool. I was destroying failed units so
it wasn't a problem. As an OT aside, they made exotic synth modules seem
like excellent value: less than £5 worth of parts, retailing at about £150,
fragile to boot, and no guarantee since they were 'competition parts'. Did a
re-design using a tougher thyristor, cleaner triggering,  and some added
spike proofing. Potted mine in silicon rubber, just in case. My local
motocross shop sold a load of them, at half the maker's price, and we never
had one back. The shop told me the works team had bought some - which is
probably why the next years's model didn't have the problem.

||\/||ike

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