[sdiy] thermal antagonists

[NSSINC]

	Seems we are always working on thermally intermittent stuff at work.
It's too hot, this does not work. It's too cold that does not work.

	Had a control board for a 750vdc > 400vac inverter that would fail when
hot. Took sending the board back and forth between the US and Czech
Republic 3 or 4 times to get it fixed. Kept coming back "no defect
found". Had to point out the square inch on the board to look at and the
temp it failed at before they finally found- an LED that would open up
when hot...

Anything with little wires can give you problems (IC, trans, etc)


-Al

		



mark verbos wrote:
> Until this year, I have not had many repairs for problems that came and
> went with heat, but I just worked on my third one this year. I find
> these issues very frustrating as they seem to be fixed and then come
> back after the module has been powered up for an hour. Anyway, the
> Buchla 227 that is on my bench right now was killing output from the
> master when it got hot. Using a heat gun, I traced it down to card 4
> when the quad mix buss with 4 vactrols ( one on each of the quad
> channels) controlling the level. Ultimately, replacing the 30 year old
> vactrols solved the problem, but this raises my question...
> 
> What parts can be temperature sensitive? I assumed a problem that came
> and went with heat had to be a trace or connector that was shorting or
> opening when the metal expanded. Is it possible that the vactrols were
> at fault or did I fix a solder related problem whilst throwing away $20
> in Vactrols?
> 
> thanks,
> 
> Mark
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