Hi All,
Thought i'd share a hairy one with ya's
I've seen this problem a few times over the decades, but i *might* catch someone else one day....
Scenario:
Measuring the +5v supply on a chip (pin), typically most people would put the POS probe on the 5v pin, and the NEG multimeter probes on the Ground pin (GND).
The problem was that there was no 5v to be seen, but when i measured a nearby chip there was 5v!
I looked everywhere for a crack in the 5v track, but no luck.....how can this be?
The problem was the chip i was measuring had an open-circuit ground (GND) track - you can't measure 5v if you have no Ground
I guess it comes form habit, we spend so many years always looking for "volts", we always ASSUME ground (GND) will be there.
So, if you see this kind of problem, you might want to put you POS probe on a known 5v pin somewhere, and put the NEG probe on various ground (GND) pins around the board to be sure you have power getting to all pins.
OR clip your NEG onto a known ground point, like the volt regulator mounting-tab etc.
Hope this helps.
Marty.
