power problem to PC

[shiatsu]

I recently aquired an old PC from a friend (P2/233) and carried out a few minor modifications to it. Everything was working fine until I switched it on this morning and there was no power. Just
dead.

My first reaction was that that the PSU (which is about 4 years old) had finally gone down. I have a new PSU and fitted this unit but the machine still appeared to be dead. However I noticed that when the power-on button on the front panel of the case was pressed a little spurt of power would apparently go through to the fans and they would turn a few times before stopping. I changed the PSU back to the old unit and the samre thing happened again! In fact if I keep on pressing the on-button I can get the CPU fan to keep spinning! But still no power to anything else.

Does anyone know what is the cause of this problem?

Maybe the power-on switch is worn out or defective. If so will I have to get another case?

Thanks, Alan

 

[PCdabbler]

Sounds like a short forcing the PSU to shut down. Try unplugging power from peripherals first (HD,Floppy,CDROM) and see if it will power up. The floppy power conncetor on the floppy pcb is my favourite. Come across it several times. It can short to the outer flat plate shielding on the drive as its not very well supported.:huh:

 

[Jmtyra]

Also check the power connector on the mobo. Make sure there are no pins bent or any debris around the pins. Had a loose piece of wire do that to me once.

Good luck!

 

[shiatsu]

Thanks for your reply

I tried unplugging power to the Floppy CD-ROM and HD but it made no difference. Regardless of whether or not the power is connected to the peripherals the PSU / CPU fans will spin a few times when the power-on button is pressed. But beyond that nothing will happen.

Do you think the M/B is dead?

Obviously that can happen but yesterday it was working perfectly!

Regard, Alan

 

[PCdabbler]

Have you had the motherboard out, making your modifications ? Try removing it from the case and reconnect the power cable and system on button to it and see if it will power up. Sometimes the stand offs that support the motherboard can be in the wrong position and short things out underneath.

 

[shiatsu]

Thanks again,

I'll try that but will probably have to leave it till the weekend.

Alan