"robb" wrote in message
...
i have a micro-controller board with 3 big 40DIP ICs, 10 or so
16
DIP support ICs. with 32v/8v/5v transformer supply

i believe the 32v shorted with 5V line

So....where does one start to diagnose such a *big* problem ?


I can only work on this in short segments of time and am usually
tired ... so i am moving backwards.

Anyway the revisit.

The last diagnostic consensus was to remove voltage regulators
and inject a good 5v power into the 5v lines and look for
warming components to get a fix on problems to repair.

Since my 5.2V *aged* lantern battery power supply did not impress
many i cobbled a simple 5v power supply from a 18 VAC/2.5A wall
wart, a 100V/1.5A bridge and 7805 5V regulator plus some
resitors and a 6V bulb to test.

I connected the 5v (through 450 Ohm) to the PCB 5v and 0v lines.
i measured ~60 mA curent nothing warmed ...i idecremented the
resistance by 100 for each iteration of testing the measured
currernt increased slightly until i made it to (100 Ohms) and
then the current spiked to ~+ 1.5A and the 7805 fried ?

but still no heat on the board anywhere, no trace no component no
IC ?

do i need to do something different with power supply test ?
thanks for any help,
robb