PC turning off during start up

[EazyB]

Hey guys i wasn't sure where to post this so i hope i picked the right place.

Last week i purchased a custom built PC. At first sometimes when i would turn it on first thing in the morning it would power off during start up. I thought that this may have been because i had been shutting the computer down but not flicking the power switch at the back off. So i would flick the switch off and on and start it up. All would be fine.

Now the problem is happening more then once. Ill turn my computer on in the morning and it will power off during start up. It powers off at different stages sometimes even reaching the desktop before it goes off. After powering off it will turn back on again after 1 or 2 seconds only to turn off again during start up.

After a while it will work but this isnt until like 12 and can be quite annoying.

I have tried different sockets and have compared the voltage in the BIOS and it all seems to be the same. one difference i noticed was the cpu rpm was slower.

I took it back to the shop but it ran fine there. But it wasn't really morning.

I hope that is enough information any help you could provide would be very helpful =D

[efus]

So, after 12 (am?) does the problem disapear? It sounds pretty random.
I would try using a different PSU.

[EazyB]

well the thing is i wouldn't say it is always 12. The time does seem to be quite random. After it starts working i can switch it on and off with out issue. Also i tried leaving it on overnight twice and it would be off when i woke up. Which is weird because it usually tries again shortly after. Maybe a safety feature stopped it re powering...

Trying a new PSU would be good but i don't want to buy a new one if it turns out to be another issue.

Hopefully someone cane shed some light on this strange problem

[EazyB]

Also im not sure if this matters but the voltage in bios was normal when there was a issue so that would mean that the PSU is doing its job wouldn't it?

[efus]

But the pc turning off at random could suggest that it didn't. :) as long as the psu works correctly the pc should stay running. Only when it fails it shuts down.
You could also try taking all hardware out of the machine. So only have the motherboard, cpu, ram and psu in. Turn it on and see if it shuts down. If it does not, then put one piece of hardware back in, turn it on again and see if that makes it shut down. Countinue until the pc is fully assambled or it starts shutting down again.

[JOSheaIV]

Check your BIOS! Some motherboards have timer functions on them. I know they can turn them on, maybe they turn them off.

Also check your CPU temp! I had a buddy make a custom build, he brings it to me telling me it keeps shutting down on start up. Well he used the cheap intel heatsink that came with his CPU. So first check your thermalpaste, then your heatsink, this can be the problem.