Power supply doesnt turn on when p4 is connected

[matthewspj]

I was putting together a pc for my friend. We got all the components
connected properly on the motherboard. But when we turned it on the
computer wouldn't boot. The green light led on the motherboard is on
but it won't power up. So tired identifying what the problem was but
taking out everything and trying it all one at a time. So with just
the power cables plugged in, that is the 24 pin connector and the p4
cable molex connector plugged onto the board I tried starting it up
and it still did not work. I removed the p4 molex connector from the
socket on the board and the turned it on and the fans came on but the
it didn't display anything on the monitor obviously because the 12v
power to motherboard via the molex cable wasn't plugged in. I'm not
able to identify the problem please help.

 

[cmichael138]

Sounds like it could be a faulty power supply. What brand and wattage is the PSU?

 

[matthewspj]

its not the psu, i tried another working psu on the same motherboard and the same problem as before, 350w. i tried the same psu on an older board and it works fine.. i think it could be something on the motherboard