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Computer wont power up

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March 20, 2009 11:32:20 PM

Hi everyone,

For the last week or so my computer has been nasically lifeless and I'm starting to turn prematurely white trying to work out what the problem is.

To start with here's a bit of background, about a week leading up to the current issue when I went to turn on my computer in the morning I'd get a brief light up on the front then nothing. If I switched the comps power off on the psu then turned it back on after a little while I could usually get the computer to start up properly and everything would run fine until the next day when I'd have the same problem. About a week ago this no longer proved effective though and now if I turn the comp on and off at the psu then try turning it on at the front I'll get the brief flicker of lights then nothing.

I've been looking at troubleshooting pages for the last week trying to determine what my issue is and I believe that I've pinned it down to either the psu or the cpu but I lack the technical ability to really be sure and before spending the money to replace the part/s I'd like to get some advice from the community.

Some of the tests I've run;
1. unplugged all unneccessary hardware/no difference
2. cycled through all 3 ram cards using different slots/no difference
3. tested psu by shorting green to black wire with pin/no difference BUT if I don't have the 12v cable connected to the slot which my motherboard guide tells me is for the cpu I'm able to short green/black wires and get the comp to start up, hard drives spin, ram lights up and fans turn on.

This last test seems to indicate to me that the issue is to do with either the cpu or the psu. I tried removing the cpu and leaving the cpu power connected to see if I could get a startup via the short method but had no luck. Now one thing I've noticed as I've been tinkering is that the thermal seal between the cpu and its fan seems to have deteriorated/possibly no longer exists. I'll be picking up some thermal paste to replace the seal later today, will a computer boot without the seal present? All tests using the short method were done without the cpu fan being plugged in so if this does make a difference please let me know.

I know I've probably already typed too much but I'm not sure what is and isn't relavant. Parts wise my cpu is a pentium 4, I've got a foxconn 955x7aa motherboard (which doesn't have any leds for troubleshooting) and my pwoer supply is a 450w antec unit.

I'd really appreciate any help forum members can provide as I really am out of my depth with this.

Thanks for any replies,

Owen

More about : computer wont power

March 22, 2009 4:28:16 PM

try to replace motherboard battery. It looks like a giant watch battery.
March 22, 2009 9:20:57 PM

Thanks for the reply meliana,

I'm dropping by the local electronics store today to pick up some thermal paste and had decided to replace the lithium battery at the same time as a matter of course. My understanding was that if the battery was causing the issue my computer should be able to start up at least far enough to give me an error. I'll replace it and reapply the thermal seal on the cpu later today and see what happens. Am I right in thinking that if this doesn't fix the issue then I probably need to replace the cpu? Are there any more tests I can/should run before doing so?

The computer fair in my city is this saturday so I'm hoping to pin point the problem before then so I know which parts to buy.
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March 23, 2009 3:48:57 AM

Pipcked up the replacement lithium cell and applied a new coat of thermal paste today. Result = same situation I was in before minus $8. At this point I'm assuming that it's my cpu that is causing the issue but I'm really just not in the position to make an informed decision. Any advice that the community can offer would be very much appreciated.
March 25, 2009 5:46:36 AM

Any more suggestions at all? My hair is turning white over this whole ordeal.
a c 122 B Homebuilt system
March 25, 2009 12:43:32 PM

CPU's really do not fail that often. Of the two components that you mention, it's more likely the PSU.

When you ask for help, you need to post complete specifications of your system.
March 26, 2009 9:46:47 AM

sorry I wasn't sure which specs were relevant .

specs are,

PSU: 450w Antec PSU

RAM: 2*512mb sticks of corsair DDr2 XMS2-5400
1*1024mb stick of something else

Motherboard: foxconn 955x7aa-8EKRS2 LGA775 P4 i955x board

Graphics card: Viewpower GeForce 7800GT 256mb PCIx 16 video card

CPU: Intel Pentium 4 640 3.2 GHz processor LGA775

HD: 2*250Gb Samsung 7200rpm SATA300 HD

cd/dvd: LG 4167 dvd/cd R/RW

Also have a 3 cooling fans which all seem to be working.

I've been advised by a friend that the motherboard appears to be the most liekly culprit rather than the cpu/psu. I'm finding it quite difficult working out a replacement motherboard that supports the rest of the existing hardware (originally looked for the same model but there don't appear to be many floating around). Assuming that the motherboard is indeed the culprit could anyone suggest a good replacement for my foxconn one? I'd rather not downgrade the motherboard but I don't need something fancy either, the closer to the existing board the better (and the cheaper the better as well the way my savings are going).

Monthly computer fair is on in 2 days, as always I'd love any suggestions board members can give me.
a b B Homebuilt system
March 26, 2009 2:49:01 PM

I agree the PSU is a more likely culprit than the CPU. CPU's rarely just wear out from age. But it's a relatively common story for capacitors in the PSU to deteriorate slowly until they get so bad they cause problems. But just be aware that the same issue can affect the mobo, since it has a lot of capacitors and resistors involved in voltage regulation for on-board components. That's why your friend suggested the mobo as a possible trouble source.

If you can, try to borrow a PSU from someone and swap that into your machine. If it solves the problem, you know what to buy. Just be sure it has enough power for you - testing with a too-small PSU still might not work, and you would not know why. If the only loaner available is marginally small, you could try anyway and just disconnect a few unnecessary peripherals like a second HHD, your DVD drives, etc. to lighten the electrical load temporarily.
May 6, 2011 7:54:44 PM

I've got the same issue going on as this person. I've replaced my PSU, so I know its not the PSU anymore, not to mention, I attempted the 'paperclip test' that was mentioned in another forum and both the new and old PSU's continued to run as long as I held the paperclip to the green and black wires in the 24-pin connector while it was plugged in. With MOBO completely stripped down to nothing, everything reseated, and nothing but the CPU w/fan, I get the few seconds of brief power and then nothing. Now, I can ONLY get this to happen if I switch the power supply off for a few seconds and then back on. Thus, I have narrowed it down to my MOBO or the CPU. Given that all the capacitors on my MOBO look just fine, I am leaning towards the CPU since the brief power up happens whether or not the CPU is in the mother board slot. And for the record:

MOBO: MSI 785GTM-E45
CPU: AMD Athlon (AD750WCJ2BGH)

Everything was bought as part of kit about a year ago.
July 29, 2011 8:18:22 PM

I have the same problem with mine, just stopped working one day.

Has anybody found out what's wrong with the motherboard?

Cant find a direct replacement wither so might have to upgrade the lot!
!