strange automatic powering down issue...

[xirokx]

Hi there,

I replaced a like for like mobo in my friends system.

When I turn it on, the pc posts then when after the post screen the system just automatically switches itself off.

I have checked all connections, reseated RAM, reset CMOS, everything I can think off, I have even tried a diff psu...

I am running out of things to check, can someone please help?

thanks in advance..

[Ulti]

Is there anyway you can check the BIOS boot code?

Seeing as it gets to the post screen I'm guessing there's no problem with the actual motherboard, is the CPU cooler mounted properly and the fan plugged in? Usually the pc automatically switches off if the CPU cooler is not mounted properly or the fan is not plugged in. Don't think it is to do with RAM or HDD or graphics card if it automatically switches off.

I really think it is a CPU/cooler problem.

[xirokx]

i double checked the cpu and the hsf...

i noted whilst the topside of the cpu had paste on it the hsf did not, does that suggest to you it is not making contact?

hsf is plugged in correctly as the fan spins

[Jay]

I think it needs new thermal paste, sounds like an overheat cut off.

[Ulti]

Either there's not enough or you didn't mount it properly if there's none at all on the heatsink.

[xirokx]

the hsf is one of those old skt 775 ones which you screw into the mobo with 4 screws...

i have checked it and there is only one way to insert it but if its not touching the cpu then i must be doing something wrong..

hmmmm

[TS || Slick]

from experience the 775 coolers are always a bit iffy especially the push through ones, the processor needs a thin layer of thermal paste dont slap it on thick thatll counter act what your trying to do. The cooler needs to be touching the CPU paste with a good firm contact, it does sound like a thermal throttling problem (a built in feature of all modern cpus) the easiest way to check is if you can get into the bios there should be a pc health status section go into that and check the cpu temp, if its at anything above 30C ish and starts rising fast youve got a problem.

You dont realise how fast CPUs get hot, just the other day i was testing a P4 in work without a HSF got to the bios and yeah it was working switched straight off, literally on for a couple of seconds, tried pulling it out and i burnt my hand.

[k4p84]

If you find it difficult to mount a cooler in situ take the board out of the case and install it.

This way you can bench the rig to see if you have got it sorted.

I know it is more difficult to subsequently mount the board in the case but if it fixes the issue......

I will agree that it sounds like you are hitting t-max.

A simple test for contact with the cpu is to put your paste on, screw down the cooler then remove it. you can see where the cooler is making good contact.

Remember with TIM less is more, really small amounts spread across the die is best.

Regards

Ed