Desktop not starting

[shrapers]

Hi all,

New to the web site which looks pretty good and I was hoping one of you could give me some advice.

When I start my computer I can hear the graphics card fan (loudest one) start up and the front panel power led comes on. After about a second the fan cuts out then instantly restarts and the power led turns off then on. This process keeps repeating. The monitor does not power on and there are no bios beeps. These are the things I have tried:

CMOS reset
Disconnect all drives, fans, usb card, sound card, graphics card fan, cpu fan. Basically every thing bar the graphics card itself.
Checked the psu voltages with everything unplugged by linking the
PSU on pin to ground. These were all within 0.1v. (my rubbish multimeter maybe to blame for this discrepancy).
Checked the 5v supply while the computer was trying to start and found the voltage was dropping to about 4v everytime the system was cutting out.

My thoughts at the moment are 1. The PSU is breaking down under load. 2. There is some kind of problem with the motherboard.

Any thoughts on this would be gratefully received.

windows 7 64
Asus p5b motherboard
Intel Core 2 Duo E6600
3gb corsair ddr2 800mhz
casecom 500w atx psu
zotac 9800gtx 512mb graphics card.

Cheers

Shrapers

 

[Quickpaw]

Plug everything internal back in, unplug the power cable on the back. While touching the case remove all your RAM, then hold the power button for 20 seconds. Reinstall RAM 1 stick at a time to test for defective RAM and try to power on with each stick

Check that the back of your mobo isnt touching the case at all and causing a short

If that fails, test with different psu, test with onboard video or different gpu if you can in case this defective one is causing issues.

That will basically tell you where your machine is having trouble.

 

[shrapers]

Thank you for your quick reply.

I have just tried testing the ram as you suggested with no change.

I doubt the motherboard is touching as its been working for over 6months without me opening or moving the case. However I will double check later.

I have no spare graphics card but I do have a couple of 250w PSUs from old computers. Do you think one of these would be enough to power my system? If not, could I power the hard drive and fans etc from one and the mb from the other for testing purposes?