Pc turning on via motherboard but switching off via front power switch :(

Ok this evening my PC decided it had enough with the world and turned itself off.

The specs are Antec p90 case, Tagan 600W dual-engine PSU, i7 920, Asus P6T MB, 6GB Corsair XMS (3 sticks), H50 Corsair cooler & GTX260 Geoforce. Yes not bleeding edge but has done well for me over the past 18-22 months.

I've tried a few things to narrow down the issue & I'm now at the point where the only stuff in the case is the PSU, CPU and CPU HSF. The front power switch will only bring the machine on for something like a second tops then it all powers down. If I use the switch on the MB the MB does seem to power up along with the HSF (I can hear the pump and sloshing water noise).

Where now? If it had been a sticking power button then it would have been more than 1 second. I'm beginning to think I have a failed CPU here (even though I've not been heavily OC'ing). Anyone any ideas where to go next? I have a 480 Watt PSU in another case in the house that I could try next hopefully. Any ideas why the MB is powering up but the front panel isn't?

Thanks :(

Try the other PSU first, its the more likely culprit anyway.

Ok just tried another PSU and it doing the same....

As the MB seems to be turning on could this be a CPU failure?

Tried paper clip on power supply with loading to single fan - all ok. Confirms that PSU is ok. Also I've found that if I hold the case power switch button down for a second the power supply will power on and the H50 starts. No boot though and Inserted the grpahics card to see if I got any post message. Nothing.

I've made no recent changes - So I'm guessing I've either got a broken MB or CPU. Any usggestions how I isolate or any way to check?

Well, if it's not the PSU, I would suspect the mobo, if it was CPU I would expect some kind of power-up, if only with a lot of beeping from the PC speaker.....but no real way to know for sure without swapping parts.

Yup thanks you've kinda confirmed my thought process was just wanting to make sure I hadn't missed anything obvious. New 1366 board it is then! :(

Cheers.

try shorting the two pins for the front panel switch using a screwdriver or similar, just to check whether it's the switch itself

Hi - should have posted to say that it was in fact the MB but I also replaced the PSU as I'm guessing the underpowered unit may have caused the MB to go in the first place!

Cheers.

did u try the mobo ou of the case but with some parts attached to see if the board was touching the case and shorting it out ? have read some other threads with similar issues and the fault disappeard when the mobo the was out of the case