Franc Zabkar wrote in message
...
On Sun, 26 Jul 2009 15:59:23 +0100, "N_Cook" put
finger to keyboard and composed:

was intermittently failing to power up , now no power up.
mohmeter reads 0.13 ohm +/- 0.01, loading the 5V rail to ground on the
main
board, HD etc disconnected.

It would seem to me that such accuracy would allow you to narrow down
the general location of the short ... unless the PCB has large power
and ground planes.

Not any of the 10 electrolytics or a power 3
lead SM device. What to try next , monitoring the 0.13 ohm while flexing
the
board. ?

Is there a TVS (transient voltage suppression) diode?

Powering with a current limited bench power supply set at 5V ? oh
for an IR camera for a piece of test gear.
If the big BGA chip gets hot, then a chuckit job.

I would think that most of the larger chips would be powered from 3.3V
or less.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

I suppose solder a good thick lead to the groundplane, for mohmeter, is the
way to go there.
Would a SM transient suppressor have a distinctive package./ overlay
designation?
I assumed the SM 3+1 lead device was a 3.3V regulator "shorted" between 0
and 5V, logo looks like DN in a circle