View Full Version : comp turns on then off real quick

Q man
30-08-2010, 08:29 PM
Hi all

Just fixing a Mates computer
The problem is that when I turn it on all fans and lights turn on for about 3 secs then turns straight of again
The comp is an old 939 socket but has new what looks like a newish k8 gigabyte mobo and power supply
I have changed power supply and ram and reseated everything and tried onboard display and checked atx connection, and still the same thing.

Any ideas what to try next? it doesn't start anywhere near long enuf to post, I imagine its the CPU or mobo but I'm leaning towards the CPU but i don't even no anyone who has an old 939 socket and CPU to check

30-08-2010, 08:40 PM
CPUs very rarely fail. It is most likely the motherboard. Another option - have you tried unplugging everything except the motherboard from the power supply? Things like hard drives can have power faults that cause the power supply to cut off.

Q man
30-08-2010, 08:52 PM
I think I'll just tell him to update the mobo and CPU, I have tried it with nothing connected but sadly nothing, thanks for the help

30-08-2010, 09:27 PM
Could be overheating if the CPU has been taken out and thermal paste not re applied.

Can you get into the BIOS at all?

31-08-2010, 09:00 AM
Check all the caps on the mobo and make sure they're not bulging or leaking .... had a similar problem and caps were the problem.

31-08-2010, 12:12 PM
If the motherboard is new, perhaps it was installed badly?

Check for short-circuits under the board (standoffs) or I\O shield (some people manage to get tabs for the USB port stacks stuck IN the ports)

31-08-2010, 12:53 PM
It might pay first to check that the power switch is not sticking. The bios may be set to power down after 4 seconds of holding the power button in. Don't laugh, it has caught me out before..

31-08-2010, 12:54 PM
I would whip the board out of the case and put it on a non-conductive surface, (to rule out any shorts, and anything plugged into the board causing it to shut down) and only plug in the power supply and screen and use a screwdriver to short out the pins and see if it still happens.

Giggity goo.

31-08-2010, 01:09 PM
socket 939 , its OLD. Probhably bad caps or just faulty mb.

Also unplug any internal USB cables, these can go bad.
Actually unplug all cables is the best way(as the post above) & use another PSU & RAM to test