Is it my motherboard ?

So you switch on and the system begins to operate and you hear a fan or fans running but then they stop running and it goes quiet and then the fan(s) run again after a short time...

My expertise is weak and limited but this is symptomatic of a defective power supply especially if you have not seen a Power OK led on the motherboard...

The electronics on the motherboard are waiting for the power to stabilise before doing anything significant - power OK from the PSU (I believe) is not being seen and after an interval the motherboard shuts the power supply down as a safety measure.

But the machine is still switched on so the whole thing starts over as they say in America.

If you do decide to change the PSU fit whatever size Wattage suits your pocket (or even borrow one from another machine as a dignostic aid) - PSUs are usually over rated to allow for future add on expansion. I recently replaced a 350W with a 300W with no problems - two disks - beefy Graphics - DVD/CD writer and Floppy.

Good luck...

P
October 2009

Now when I try to boot it , it starts up and then about 5 seconds later it turns it self off

Dave
October 2009

yes external HD has sinse been put away ! I forgot to mention last time, whether it matters or not but the fan keeps reving up every now and then ?

Dave
October 2009

So presumably the external Hard Drive was connected to the mian box and both were powered on at the time you put the cover on and caused the short to happen?

This may have sent stray voltages into the computer and caused one problem with the motherboard or multiple problems. In an ideal world none of this should have happened - putting the cover on should not have caused a short - but it did. I still suspect the computer power supply though and still feel that the motherboard should be showing a led light to indicate that the power is OK - Motherboards are much more expensive than power supplies - a ten minute fix.

You have permanently disconnected the external hard drive I presume.

Continuing good luck...

P
October 2009

Hi Peccavi , 1st of all thanks for replying, I had to put a new casing on the external HD cos the old 1 had broken. When I tried it out there was a brass/copper bit of the power supply of the external HD that had touched the outer casing , it sparked and then my trouble started. I have checked for a light on the motherboard when I tried to boot it but couldnt see it, I actually had a look if there was a light/diode but couldnt find 1 on it, the motherboard is a "GA-8TRC410MNF-RH if that helps, if it was the psu would the fan on the processor still work ? with taking the memory out and trying that, I didnt know what that would prove either , but tried it anyway.

Dave
October 2009

It was ok until...

"I had a external hard drive connected to my pc via usb which shorted out"

How do you know something "shorted out" ?

What was it that shorted?

If you run the machine with the cover off can you see a Power OK light on the motherboard (often a green LED) and does it remain lit? If it does stay on then the PSU is OK.

After an incident like something shorting out I would suspect the power supply first and the motherboard second - much will depend on what shorted to what.

I'm uncertain what impact taking the memory out will have - I can't imagine the memory having anything to do with your problem - or the graphics card.

Good luck...

Peccavi
October 2009