Computer won't start

[PassnThru]

I'm typing this on a perfectly functioning computer. However, if I shut it down right now it will not restart. When I press the power button absolutely nothing happens. Fans don't spin, leds don't come on - nothing. If I turn off the power supply and turn it back on it will boot right up. This is consistent - every time.
Now, a few months ago, the opposite was happening. When I shut it down it would keep running. Windows would shut down but it was obvious that some power was leaking to the motherboard. The fans would continue to spin slowly (sometimes jerking) and the hard drive lights would be dim - the DIMM LED on the MB would actually blink. I finally determined that the power supply was the most likely culprit so I replaced it with an Antec SmartPower 2.0 (400W) and everything was back to normal.
Until now. The MB is an Epox 9NPA+ with a 3500+ Athlon 64 in an Antec SLK-3700BQE case. Anybody seen anything like this before? I'm partial to blaming the MB at this point but realize that you can have two bad power supplies in a row.

[kljucd123]

Hi,
I just had the exact same problem, and it turned out it was the power button causing the problem. I would have to repeatedly press the power button, which would usually work after a while, but then I had to use the power switch at the back of the psu and shut it down completely. Once I switched to another box, this problem ceased immediately.

[PassnThru]

I pulled the power switch lead and use a volt ohm meter to check it - when pressed the continuity is good. I don't suspect the switch at this point - I can always start the computer the first try as long as I turn off the power supply first. Since that always holds true and turning off the power supply does not affect the power switch then I don't consider them related.

Oh - and you are right about turning it off. When I had the previous problem turning off the power supply was the only way to get it to shut down completely. But those problems went away with the new power supply only to be replaced later by this. You basically did the same thing by swapping your case - new case, new power supply unless the used the old one. And currently mine shuts down just fine - just won't start back up.

[PassnThru]

Discovered this morning that the DIMM LED lights up and stays on after the first attempt to power up the computer. Not sure how relevant that is but it tells me that the power button is doing something - the power supply and MB seems to be trying to start up but just not quite getting there. I did try shorting the pins where the power switch hooks up to the MB - nothing happened. Doesn't the MB always have voltage to it from the power supply? If so, which pin is it on the main power connector?

[aroraharmeet]

I know its been a while but were you able to figure out the problem with PC? I seem to be having the same issue.
DIMM LED lights up and stays on after the first attempt to power up the computer.
Have Epox 9NPA+ and Antec SmartPower