Question PC powers up without pressing power button

[steveis2]

Hi,
The PC will power up as soon as I plug in the power socket but before I press the power switch on the PC. It doesn't always happen. Usually it happens after the PC has been on for a while then switched off but then the plug put back in the wall a little while later. If I leave the PC unplugged for about 10 minutes the power up when the plug is plugged in doesn't happen.
No other PC I have ever had has done this and I suspect it's a fault with the power supply although I could be completely wrong. Any ideas about what is happening would be appreciated.

Regards Steve

 

[stonecarver]

In bios make sure automatic restart after power failure is not checked as default.

 

[steveis2]

Hi
Thanks for the suggestion. However on looking through the BIOS and the manual of this old motherboard I can't find anything that specifically refers to a restart power failure. It's a GeForce6100PM-M2 motherboard combined with a sempron CPU, running windows xp. So it's very old.
I've been removing one by one the various front panel connectors but that doesn't make any difference.
Perhaps there's some sort of short circuit or even a cob web somewhere. I know the power supply is ok as I replaced the original one with a relatively new one that definitely has no problems.
Apart from a problem with the motherboard itself I can't think of anything that could be causing this. Although if there are any other possibilities I'd follow it up.

Steve

 

[stonecarver]

I could be just your power supply. I have computers on a KVM switch and if we have a power bleep three of the computers will stay off and one always reboots. Non are set to reboot on power failure.

Try this unplug computer from wall just after using it. With the computer unplugged hold down the power switch for 20/25 seconds. Than re plug in computer. Does it come right on again or wait till you hit the front panel power switch.

I just chalked it up to the caps in the computer hold charge just a tiny bit longer than my other computers.