power down problem

[smorreale]

Built an AMD socket am2 system. Ran fine for 3 days. Tried to turn it
on day 4 and it will not turn on. When I hit the case switch - all
fans spin (cpu, case, power supply) for 1 second and then system powers
off. There is no time for beeps, post, screen text, etc. If you
immediately hit the switch again, fans spin for 1/2 second and then
system powers off. Hit it again and fans barely move. Hit it again
and nothing at all. If I pull the plug from the power supply and plug
it back in, I can start the cycle over again - I get 1 second of fan
time again.

I bought a power supply tester and it tests OK. I bought a new
motherboard (exact model as old) and system acts exactly the same. I
patched in the case power switch and reset switch from an old case and
still no difference.

This may be coincidental, but the last action I performed on the
working system was copying data from a corrupt IDE hard drive. The
boot drive is a brand new SATA.

any ideas? - should I buy a new power supply (does tester really test
everything?) - could it be CPU or RAM or HD. What can cause instant
power down????

 

[JAD]

PSU regardless of the 'ok' test.
If you used the plug in tester it really doesn't 'load' the supply.