What may be wrong?

[petrusbroder]

I just had a very busy week and have not had the time to look it up ... and I need some advice:

I have a computer (AMD Phenom II, no OC) with 3GByte RAM, on board GPU. The problem is it shuts itself down 1 - 2 seconds after I power it up. No beep signals.
I have had this problem before but when I tried to start the computer before, it started at the third or fourth try. Then it worked perfectly for weeks and weeks until I shut it down for maintenance (dust removal).
The CPU-fan works (it lights up and turns as it should), the PSU-fan does so too.
If I start the computer with one stick RAM, keyboard and nothing else, the same problem persists.
It is not the power switch, I get the same result when I use a screwdriver to short the appropriate pins.
For once I do not have any spare parts to test with and my multimeter is broken - so I can not measure the voltage of the PSU.

What should I get? A new PSU? A new motherboard? Is the CPU gone? I know that the RAM does not matter, I have tried different sticks with no change in the behavior.

 

[Markfw]

I would says its most likely motherboard. PSU is the second choice. CPU is the LAST choice.

Question, can you get into bios ?

 

[ZipSpeed]

Educating a guess but it's probably the PSU.

 

[petrusbroder]

I would says its most likely motherboard. PSU is the second choice. CPU is the LAST choice.

Question, can you get into bios ?

No, I can not. It won't even start the BIOS.

 

[Rudy Toody]

You have ruled out the polarity of the power switch, so the only thing that could give the same symptoms is the 12V line to the MOSFET.

Make sure the 12V next to the cpu on the mobo is connected. If it is already connected, then I would guess that it is the psu.

 

[Philippart]

my guess is the psu

 

[theAnimal]

What PSU model & how old is it?

 

[dajeepster]

unplug the power cord from the psu... wait a few minutes, and then plug the powercord back in and try powering up again.

sounds weird, but i had a machine act like this way back when... don't know were that machine is anymore.. but i think it had something to do with the motherboard... oh.. and i think it was a dell too.

 

[kb3edk]

Hi Peter -

What make/model motherboard? All other things aside I suspect this could be the infamous "140W Phenom II in a 95W motherboard" issue... some motherboards are known for falsely claiming they can support 140W Phenom IIs when they are really only built to the 95W specification.

The symptom you are having (no POST) is what others are seeing who have encountered this issue.

However we definitely can't rule out the PSU either.

It's probably not RAM as you have already tried several sticks, and I doubt it is CPU as the main symptom of all dying CPUs I have seen is that they boot into the OS and then hang up/blue screen a few minutes later.

So yeah, 99% it's the motherboard or PSU. Two times I have had this issue you report, and once it was the motherboard, and once it was the PSU...

Good luck,