BleepingComputer.com: PC turns on and then off again after 4 secs

Hi there, I am trying to repair a Packard Bell Imedia 2215. It's got an ECS MCP73VT Motherboard and Intel Celeron Dualcore processor. All it's doing is turning on and then off about 4 seconds later and there is never any monitor activity no matter how much i rattle the keyboard (pressing lots of keys). I have tried a few other things so far which include:
removing all hard drive power and SATA cables.
Then i tried taking out the RAM and powering up with just the power lead attached but still it does the same.
I have removed the battery and shorted the CMOS reset pins.
i've re-seated the CPU and re-applied heatsink paste.
removed motherboard and checked for shorts and burnt tracks but found nothing untoward
Testing the PSU with a tester
Tried a known good working PSU

nothing has worked

So i am thinking obviously something's broken but can anyone tell me whether it's the CPU or Motherboard ..

Just giving a shot at it.

I had once a similar problem and it turned out that one of the usb ports were broken and the metals were touching and shorted the comp. I only figured it out after disconnected the front usb from the mobo...

Otherwise I haven't much more I can add.

Good Luck!

Hi thanks for a quick response.

That's an interesting theory and one i hadn't thought about. It was worth a try but the USB ports look OK and i have tried the mobo without the front leads connecting.

So far my biggest theory is that the mobo is functioning OKish but is not happy with something connected to it, normally if no memory is plugged in it would beep almost as soon as it's turned on but it doesn't seem to be getting as far as checking that which leads me to think that it's the processor

I wonder if anyone else can tell me whether their machine has behaved something like this after some over the top overclocking or something

"Then i tried taking out the RAM and powering up with just the power lead attached but still it does the same."

When you remove all the ram from the system do you get any beep codes?
The system should check for ram on post and complain that there isnt any.

My thinking is that if it does not do so you may have a bad motherboard.

Well this is the thing, there is no beep at all from the motherboard no matter what is plugged in or unplugged so i too thought it was the motherboard but then would a broken motherboard function enough to shut down?

With the 4 pin CPU power supply disconnected it stays on and the fan continues to run at full speed so what if it's trying to initialise the processor and getting stuck there?

Also can anyone who has ever owned a PC with this type of mobo tell me if there is power from the USB port when the machine is powered off? That will give me a big clue. Some of my older PCs worked that way

This post has been edited by misspiggysdad: 25 May 2011 - 02:07 PM

i had a similar problem with a HP model and i reset the BIOS via the jumpers on the MOBO and it worked for me, just something to try.

Thanks for that suggestion but I have tried resetting the bios by shorting the the one jumper on the board that is available, it hasn't worked.

I wonder if anyone can tell me if there is a certain combination of keys that i can press at switch on that will invoke some sort of BIOS recovery? I revived an old PC by pressing Ctrl + Home and that worked (didn't work on this one)

Did you try replacing the CMOS battery with a new one?

Batteries don't last forever...at least, the ones I buy don't.

Louis

Well i'd like to think that a computer will not refuse to power on (and stay on) just because of a flat CMOS battery that would seem like a pretty big design flaw, but i'll try anything once no matter how unlikely it is to work! So i did replace it with a brand new one ... no joy, I've even tried it with no CMOS battery at all but no joy there either.

If there was just some way i could work out whether it's the processor or the mobo, unfortunately i don't have another socket 775 based unit and i'm not in touch with the owner so i don't know what he last did on it before it packed up

This post has been edited by misspiggysdad: 26 May 2011 - 04:18 PM