Re: gEDA-user: sparkfun 4 layer boards

[Eric Brombaugh <ebrombaugh1@xxxxxxx>]

Mark Rages wrote:
> 
> I've had moderate success clearing blind shorts with the 5V bus of a
> high-power computer power supply.  (This can be hazardous to other
> parts on an assembled board)  Otherwise, use a current-limited power
> supply to put a few amps into the stuck node.  Use a millivolt meter
> to measure different places on it.  Lower voltage means closer to the
> short.

An IR camera to look for the hotspot would probably be a handy way to do 
this too. Who's got an IR camera though?

FWIW, strange shorts can happen on high-end board mfg. lines too. I 
recently had a fairly large board used in my day job start smoking after 
several hours of use. Tracked it down to a power via that internally 
shorted to a ground layer. Destroyed the via, carbonized the board and 
de-laminated the top layer in the vicinity, but after I drilled it out, 
removed debris and sealed with solder-mask touchup the board is usable 
again (one-off prototype with several hundred dollars worth of fast 
ADCs, so we preferred not to junk it).

Eric


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