[sdiy] strange PCB faults, was:OTA question

Paul Perry pfperry at melbpc.org.au
Sat Sep 18 03:43:27 CEST 2010


I was once asked to fix a stereo that allegedly had
"got a little water on it from being next to an open window".
Well, it didn't take much sniffing to realise it was cat pee..
and suprisingly conductive..

I've had a buried conducting short in stripboard as well - again like Harry,
only the once - but 'once is enough'.

And yes, corroded leaking electrolytics can spread over an area,
given time and cycling humidity.

paul perry Melbourne Australia


----- Original Message ----- 
From: "Ingo Debus"
> Am 17.09.2010 um 14:51 schrieb Harry Bissell:
>
>> seriously, was it a copper clad perfboard ?  Sometimes there are
>> faults in copper-clad
>> where there are subterranian short circuits (contamination in the
>> laminate that can
>> join unknown circuit points).
>
> Recently I tried (in vain) to fix a stereo amp, whose PCB in some
> places obviously was soaked with something conductive. The stains
> were visible, and when I placed the test leads of my ohmmeter on the
> PCB it showed a few megohms. Cleaning didn't help much.
> Could this come from a leaking electrolytic? Do lytics leak that much?
>
> This amp was oscillating, and I couldn't fix it. Probably unwanted
> feedback paths all over the place.
>
> Ingo




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