Re: Finding power - gnd shorts

On Jul 23, 3:17 am, Neil <NeilKu...@xxxxxxxxxxxxxxxx> wrote:
rickman wrote:
I have a small module that is shorted between the +12 volt plane and
ground. I am having a hard time finding where the short is so it can
be fixed.

The bare boards were supposed to be tested, so I don't suspect the
board itself. I have visually inspected everything I can including
looking under the chips as much as I can see and found no sign of a
problem.

My bench supply current limits (foldback actually) and I am seeing
about an Amp into the 12 volt rail. Probing with a volt meter I can
see 10 mV at the point where I connect the power to the board. This
drops to about 1 mV on the other edge of the board. But I can't find
a particular point where the voltage says "here it is"!

Any ideas on how to find and fix this short?

Rick

If it is a lot of board, and they are not too expensive, Try more
current. 1 amp is a lot. Something should be getting warm. If it is
not the board, that leaves wrong / bad components, backwards parts, and
a schematic error.

Many posts indicate that I should expect the something to be getting
warm from the 1 Amp of current. Yes, the power supply is getting
warm. The voltage on the board is only 5 mV max. That equates to 5
mW. I think it would take a very sensitive device to see the
temperature rise from 5 mW of power. Handing the board wearing gloves
would leave a larger thermal imprint than this.

But using a FLIR camera does sound like fun!

Rick
.

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