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Old December 28th 15, 11:17 PM posted to sci.electronics.repair
Bob Engelhardt Bob Engelhardt is offline
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First recorded activity by DIYBanter: Jul 2006
Posts: 2,443
Default Baffled by cordless tool problem

I have a Milwaukee 12v cordless jig saw. It was working fine then
stopped, dead. Then started again, with no symptoms. It did this back
& forth a few times, then stayed dead. It never stopped while being
used - it just wouldn't start at all.

I took it apart to diagnose & as soon as I put it on the battery, it was
OK! I reassembled it and periodically tested it over a week. Always
OK. Today I put the base/shoe back on & it was dead!

As I took it apart again, I kept checking it, but it didn't come back.
And then, sitting there, it did come back, spontaneously.

It has a small PCB for speed control. The PCB also controls an LED
"work light", which comes on when the battery is connected. Except when
it's dead - making the LED a good go, no-go indicator. And showing that
the problem is more basic than speed-control circuitry.

The PCB has a number of wires soldered in through holes. I have checked
all of them. I have stressed the board with mild twisting; I've cleaned
it with carbon tet; and have warmed it with a hair dryer. Nothing had
any effect.

The board is SMT (with a 48 pin chip!), except for the wires, 1 cap, and
the output FETs, which are TH.

Is there anything else that I can try?

Thanks,
Bob