On Sat, 22 Jan 2005 04:36:30 GMT, Al wrote:

Thanks kindly for all of the replies to my previous question. I've read
twice through each reply - some will take another run-through tomorrow to
really absorb, since I do want to understand it all completely

But, I just did an experiment which tells me that the PS is probably not
the problem. I borrowed a Compaq and pulled its working ATX PS. The
resulting behavior was the same - power on for a moment only.

Does this pretty much say that the PS is not the problem here? What
should be my next step in diagnosis?

Are you plugging ALL the wires back into everything?

A) I would just have PSU into MOBO and remove everything else (except
the front panel switches / LEDS) then test again (even remove addon
cards).

You don't need yer voltmeter yet as there's little to see.

Keeping it simple.

1) Test the PSU on the bench and see if it runs (loop test etc, fan
spins etc). If it won't run on the bench it won't run in the PC.

2) If 1) is ok then test it again in the PC with just the wires as A)
above

3) If 2) is ok (PC passes POST etc) Then switch off and add things
one-at-a-time (FDD and Power cable and power on, if ok then HDD and
power cable etc). If you get the machine back up and working you might
have an intermittent fault or a bad plug / cable / bad device.

The above has worked for me for the last 20 years (from when PSU's
were 63 W) ;-)

All the best ..

T i m