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