PC does not post then cuts out and starts again

[andyf2003]

Hi i am new to this forum

My PC has in the last 48 hours has developed a problem.
No hardware changes have taken place in months.

On booting the PC up it fails to post then looses power(as if it is rebooting) then starts up again.
The pc continues to do this over and over again.

Eventually i managed to get the pc booted up but then crashed as soon as i moved the mouse. (windows XP Build)

Does this sound like a motherboard or a PSU problem?

Andy

 

[Nitestick]

possibly neither. no beep codes? does your motherboard have diagnostic lights and if it does could you please list their activity during this cycle. i would try and get another psu to test on the motherboard first. if it seems stable with that run memtest86 to check your ram. if not try to get it to at least run memtest as you said with persistence it did boot.

 

[andyf2003]

Hi thanks for your reply

i dont think it does have diag lights.
I have forgotten the model and number of my mobo.

I will update the topic later when i get home

 

[andyf2003]

ok so av replacement the PSU and still the same.
PC boots then b4 it posts it shuts itself down

My mobo is a: Asus A7N8X Deluxe
Memory is: 2x Corsair Pro Series XMS 3200 512MB Chipps

I ave also tried some generic 512MB memory from a dell machine

Are there any idea's what component that might be failing with this powering itself off fault.

Regards

Andy

 

[Nitestick]

for a post to fail like that it would be either motherboard, memory, cpu or psu. you've seemingly ruled out memory and psu therefore leaving cpu and motherboard. it is probably more likely that the motherboard is fried

 

[Blueman]

Sounds like your power switch is stuck in. this would cause your system to start up and turn off, then cycle the power again.

Otherwise you could have a bad PSU or MTB, or a short somewhere along the power switch circuit.

 

[Nitestick]

thats also a possibility. check that.

 

[andyf2003]

Ok i have done a few more tests.

My PSU on my own pc the PSU fan will not run.

When i place MY PSU fan in a pc from work where the mobo has a square 4 pin adapter this then gives power to the PSU fan and the work pc will boot up.

I do not have one of these square 4 pin adapters on my mobo.
Yet i have had this pc running for over 18 months.

Does the PSU fan require powering on its own to enable the PC to run?

Andy