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Very strange and serious problem...unknown cause


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I'm having a serious problem and I'm not sure about the cause. Recently I began noticing my rig would suddenly power down for no reason...no windows shut down, just a sudden power kill. After much investigating i couldn't figure out the problem so i began to strip everything down (no optical drives, one memory stick, etc.). When I tried to reboot, I got one yellow LED and nothing else when powering up (connections are NOT the issue...I assure you). After doing some jostling around and moving cables, etc., I noticed that I would get the occasional power up, followed shortly thereafter by the power kill was experiencing before. I eventually took the mobo completely out of the case, and it worked fine, so my question is this:

 

Is it possible that my motherboard is shifting in my case, somehow causing the wrong part of the board to touch metal, thus causing the power outage, or is this not possible? From all the repetitive testing/moving/rearraging i've done, that seems to be the only option, unless my mobo has a short in it somewhere. I'm fine with upgrading the board if that's what's necessary, but I want to be sure something in my case isn't causing the problem (it's a cheap centurion 5 by coolermaster). Has anyone experienced/heard of anything like this before? I've done a brief search of the board and haven't found anything similar.

 

Other notes: When the mobo is in the case with no video card, either runs diagnostics up to the one red led, or it doesn't power up at all and just gives me the single yellow LED. With the video card in, I either get the single yellow LED and nothing else, or i get three reds and a flashing fourth red, or i get a single red led meaning there's no video card installed. Very strange...I think it's a mobo problem but any thoughts are GREATLY appreciated! (note: haven't tried the mobo outside of the case with a video card)

 

EDIT: loosening and tightening the mobo screws also seems to have an effect. I'm never tightening them very tight, but sometimes i have more success getting to POST with looser screws than with tighter ones, which furthers my belief that there's something going on with the motherboard and case touching each other that shouldn't happen. Also, my mobo is held in by only about 3 screws, spread apart.

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Put the PSU in another computer and see if the other computer exhibits the same issue. I was troubleshooting a similar problem at work and after all the headaches, totally forgot about the shoddy PSU that came with the case. You have a good PSU so it may be fine but it surely cannot hurt to try it...

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UPDATE:

 

I've taken the board completely out of the case so as to eliminate the possibility of metal-on-metal i was worried about before. Tried with two PSU's and two video cards. Here's what's happening:

 

I can POST up to one LED without a video card with my OCZ PSU, however, if I move the board any or move the main power cable, I get a sudden shutoff, indicating either a bad PSU (faulty wire for main power line) or bad power connector on the MOBO. I get nothing other than the yellow LEDS on the Antec PSU...no powerup at all.

 

With either video card (7900 GT or ATI x800xl) I get the same result with either card in either PCI slot - either it isn't recognized at all, or I get three LED's and a flashing fourth for a little while, followed later by the single red LED, indicating no video card is recognized.

 

Once again, I'm trying this with the bare minimum plugged into the motherboard.

 

So, I'm left to the conclusion that I have either a bad mobo or bad PSU, and possibly both. Any ideas/suggestions/comments are highly appreciated.

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Guest Spartacus

Pull out the mobo and make sure you do not have any extra stand-offs that do not match up with a hole in the mobo. If you have any of those you need to remove them.

 

The metal stand-offs should only touch the mobo at the mounting points. That provides ground paths and that's a good thing. The stand-offs touching anything else on the bottom of the mobo is very bad.

 

Also check to make sure the grounding fingers on the IO shield are touching the outside of the little tin towers that contain the PS/2, USB, and NIC connections. I have seen where those fingers can become jammed inside a USB port when mounting the mobo.

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Haven't noticed any bad solders and woudn't really know where to look. All wire connections have been checked numerous times. Where should I look for a bad solder?

 

Also Spartacus, I don't think I know what you mean by stand offs

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look at the metal pins on the mobo's main power "slot" and the main power connector from the PSU. also check the molex connector pins. Make sure they are making good metal to metal contact. I had one female pin on a molex connector that was too wide and would not make a proper connection to its male counter part, causing major problems. it sounds like your getting inconsistant power to the mobo/GPU or something due to a loose power connection.

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Another update...

 

I've hooked my OCZ PSU up to a power supply tester and it's not working...all I'm picking up is the +5VSB. I'm not sure exactly what this means but I'm assuming the PSU is defective, so I'm RMA'ing to Newegg, but I still have a problem. My Antec PSU, which works on the tester, still isn't making the mobo boot up any more. Same problems as described above when a video card is installed. Could the PSU have fried the motherboard as well?

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