I have an old HP current probe that works well for this. Just make sure the little white dot is pointed in the direction that the trace is running in. I find that the probe works best with high-current pulses best, although it will trace a DC current. The little thumb-wheel pot on the side of the probe sets the sensitivity. I also (years ago) purchased something called a "Leak Seeker" that is specifically designed for this kind of trouble-shooting. It is essentially a high-resolution DC voltmeter that controls the pitch of a tone. Its really cool in that it auto-zeros itself as you progress along the trace(s) heading in the direction of the short. You don't need to watch a meter - just listen to the tone as you move the needle-point probe from place to place along the trace. The fine-tip needle easily penetrates the solder mask. Its actually worked really, really well the several times that I've used it. Do note that its designed to locate DC faults (as opposed to pulses). dwayne At 11:20 AM 3/23/2010, Harold Hallikainen wrote: >A tech just came to me with a problem on a board. A PIC is TRYING to drive >a line to 3.3V, but it's only getting to 1.9V. So, something somewhere is >holding it down. Has anyone had any luck with Hall effect current probes >in tracing where current is going on a board? What particular probe are >you using? > >THANKS! > >Harold -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist