Desktop PC Powering itself off after 3 seconds

Holeypockets

Good evening chaps,

My other PC - a desktop has suddenly reverted to powering itself off after just 3 seconds. It is not beeping so no clues there. I have checked inside for dust bunnies - nope - clean as a whistle. I have removed the memory and tried again - same thing. I have disconnected the HD and tried again - same thing again.

I reckon it must be the power supply but have not seen this before - normally in my experience they just don't power up at all when they are stuffed. Does anyone have any other suggestions as what to try.

Thanks in advance.

ravenfire_2

It sounds like it could have a virus.

Holeypockets

Thanks for your reply, but I disagree. It isn't getting far enough for a virus to do it's nasty stuff.

The power supply supplies the motherboard at two places - one is the big white block plug (forgot the name) labelled P1 the other is the smaller squarer block (again no name). If I unplug the smaller block it does power up so I therefore think it must be the PSU.

vyseyboy

Have you tried re-seating the graphics card? Are you getting any graphical output at all?

Also, you could try resetting the BIOS - The motherboard manual should say how to do this, but if not, taking the button battery out for ten minutes usually does the trick.

Note that you might lose some settings doing this, but nothing that can't be re set-up later.

totalsolutions

It's the power on switch, could be faulty check the bios settings to shut down after 4secs

jpe20

Sounds like a graphics card to me as the power supply is probably (could still be a problem with a voltage rail failing) ok as some power seems to get through in the first place. Motherboard failure is another possibility which is hardest of all to diagnose as you have to rule out the memory, gfx card and they PSU.

I personally would try a new MOBO battery if it is 2-3+ yrs old, swap and test the gfx card from your other PC or friends PC or buy a cheap 17quid PCI gfx card , try overvolting the memory if you can get into the bios but by no more than 0.3V max for a short period. Also as a first I would try removing all memory modules bar one and just try that and swap and test each one etc with a utility like MEMTEST86 which you can download and burn onto a CD so that you can try and run a memory test.

Other final alternative b4 trying a new MOBO is to buy a cheap stick of 512MB which you know is compatible with the MOBO approved list.

I would try the memory/gfx stuff first as this is easiest to test initially.

Hope this guides you in the right direction as I am an amateur at this sort of thing.

Jools

John_Gray

If you don't feel confident in replacing the PSU yourself, perhaps try a local PC repair shop? They may well be amused at some of the suggestions in this thread!

Lord_Gardener

Don't want to depress you but we've recently had 2 desktops go down with the same problem! Turns out that PSU had gone on both machines and these had toasted both motherboards!

Holeypockets

Thanks for all the comments. To follow up...
I wiped some encrusted !!!! off a couple of the resistors on the motherboard - it looked like someone had been eating porridge off them. I was then able to power the machine up. It appears to be behaving like it is overheating - you have to let it cool down for 30 minutes to allow it to power up again. I am going to strip it completely and give it a good old blast of canned fresh air to see if that helps.

Thanks again for all the comments.