Gday peeps, I have a p4 3.2gig, I was having trouble with the pc shutting down, so through a process of elimination, I have just about rebuilt the PC.

I have even got to the stage where all I have connected is the power supply which is new. New ddr2 ram 1 gig of it. New motherboard and the cpu is new as well.

So bare bones just to power it up. If the 12v cable isn't connected there is no problem with the pc staying powered up and it doesn't shut down, but obviously it is unuseable, having to have the 12v 4pin cable connected is needed for the pc to function correctly. As soon as you plug in the 12v cable, it stays powered up for around 5 to 10 seconds maximum and then shuts down. Anyone have this before? I thought it was due to a power black out as this happened not long after that, but like I said I have now replaced all parts and it is pretty much a new pc. I am at a loss with this one, as I have been building and repairing PC's for years and never ever come across this before. :idunno:

Thanks for you help.

Is the orientation of the 12V plug correct? Most have clips that make this unavoidable but just thought I'd ask.

I can find a few similar threads on other forums but they suggest either a bad PSU or bad mobo.

Can you test whether indeed you are getting 12V down that line?

Do you have another PSU to try on this board or another board to try this PSU on?

Yep orientation is fine. I have tried 4 other power supplies, with the same result on the new motherboard, surely the new motherboard wouldn't be causing the same issue that made me get a new one?

BTW I got a different brand motherboard just in case it was an issue with the brand. I did that just to eliminate any possible thing.


Can you test whether indeed you are getting 12V down that line?
How can this be done. I dont know how to use a metre if that is what you are suggesting.

Hope I can get this sorted out as it is making me age every minute of the day lol.

Regards Malcolm

Yes I was suggesting a multimeter:

Turn the dial to the 20V DCV setting. Touch the black probe to ground and red probe to orange, red or yellow to test +3.3, +5 and +12.

But if multiple PSUs give the same result then that makes the board more suspicious.

Have you tried to run it out of the case? Just trying to eliminate all variables.

Yeah I have done that, and even bought a new case. :-(

When I had it outside the case, I only had one and then two sticks of ram, have tried both ddr and ddr2, the power supply connected to the motherboard, and the CPU and fan. Still when the 12v line isnt plugged in, the power stays on, once the 12v is connected it then shuts down anywhere between 5 and 10 seconds.

Regards Malcolm

Mysterious. Will keep looking about and pondering with you.

Will post back any findings. :takecall: