On Sat, 2008-08-23 at 11:41 -0500, Mark Rages wrote: > On Sat, Aug 23, 2008 at 12:52 AM, Dave N6NZ <[EMAIL PROTECTED]> wrote: > > Eric Brombaugh wrote: > >> > >> What sort of shorts are you seeing? I'm assuming that on a 2-layer > >> board they would ordinarily be pretty easy to correct by appropriate > >> use of an knife. Or are they internal/inaccessible? Is that even > >> possible on a 2-layers? > > > > You'd think they'd be easy to find. On the board I blindly assembled, > > there was a short to the ground plane somewhere. I spent more time than > > it was worth looking for it, and scraped away at a couple of suspicious > > spots with an X-acto knife. Never did isolate it. On the second > > shorted board, it was another short to the power plane somewhere. After > > I confirmed it, I just marked the board and threw it in the NFG pile. > > > > 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. > > Regards, Mark > [EMAIL PROTECTED]
Way back when I used to fix 16K pdp dram cards, Atari STs, Commodores, & 4MHz motherboards, :) I used the same technique to 'remove' a shorted component from the 5V rail. Most times it would be a tantalum or a ceramic bypass cap. A dab with a good 5V supply would coax the errant part to 'let its smoke out' & expose itself. If it was a TTL or memory chip, the case temp would climb after about 1 sec. Easily detected with a quick hand wipe-over. -- Greg Cunningham <[EMAIL PROTECTED]> _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
