Re: Finding shorts on Pac boards???

70 ohms is NOT a short. 5 ohms is NOT a short. Under 1 ohm is probably
a short.

A measurement of the resistance with the board powered off doesn't
really tell you much, could be just a different brand of chip used
somewhere. Could be the regulator itself. Only sure way to tell is to
apply 5 volts directly to the logic and see if it works or not (or if
something gets hot or not).

Electronicamuse@aol.com wrote:

> I have a short stack of boards that I put aside for a rainy day (or a
> brainstorm). These all have some degree of +5/GND shorts. I have
> removed the socketed parts and verified that the problem isn't in the
> PS section. Also checked other easy things like solder-side bent
> pins, etc. So, are there any easy, common problems with these? I
> have repaired many other types of boards, and just don't see this
> happen on other platforms. Maybe with the onboard PS, when it dies
> harshly, it shorts a TTL badly or something. I know that with a good
> DMM, you should be able to better pinpoint the problem area by
> checking resistance, etc. Randy Fromm has written articles of using
> an external +5 source to find a shorted node, but I am not sure if
> that applies here. Ideas?
>
> So, to be clear of the situation on these boards, they all show a bad
> +5, although the PS section seems good. Resistance between +5 and GND
> is less than 70 Ohms, where on my DMM, the value is usually 180 or so.
>
> TIA
>
>
> Dave

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Received on Sun Jan 4 13:35:05 2004