Core i5 750+Gigabyte P55-UD4P rig boots for split second, shuts off *solved for now*

[cjbee]

Long story short...had my year-old overclocked i5 750 (3.0ghz on stock cooling) doing some video encoding the other night, and the machine shut off halfway through the process. Okay...fine...I figured it was getting too hot and maybe it just shut itself down to prevent damage. From here, the solution is simple...go into the BIOS upon restart and revert the OC...

...but it turns out I can't even get the thing to POST now.

I open up the case, and notice that when I hit the power switch, the four phase LED's on the mobo flick on for a split second and then turn off. Thing is...I can't repeat this without turning the PSU off, re-inserting the power cable, and flicking the PSU back on. Thinking it was a PSU problem, I did the paperclip test and tried it in another machine...it works fine.

Did a bench test with one stick of RAM + CPU + mobo only, then alternated with a different stick of RAM and then no RAM...problem persists. Reseated the CPU and HSF to no avail as well. Doesn't look like any of the CPU pins are burnt or charred...none of them are blackened or discoloured, anyways -- they look normal. No smells of burning coming from the mobo, either.

I've tried clearing the CMOS via jumper and that didn't do anything. I removed the CMOS battery about an hour ago and will replace it shortly to see if that does anything.

But a bizarre twist: I tried to power on the machine WITHOUT the 2x4 12v power connector and it stays on for about 2 seconds and flicks off and does this on an infinite loop until I switch the PSU off. Then as soon as I plug the 2x4 12v back into the mobo, it goes back to the original problem (on for a split second, and won't come back on unless I switch off the PSU and re-insert the power cord).

What's the deal? When the local computer shop opens up in a few hours, I'm going to bug them to see if I can borrow some components for a definitive diagnosis, but until then, I'd like to hear some input just to see what I'm in for here. I can provide more details if necessary.

Thanks.

edit: just replaced the CMOS battery. Nada.

edit 2: A solution...for now -- turns out it was a short...see post #3.

 

[nboy22]

Sounds like you've got a short to me.

I would start by removing EVERYTHING from the case and stripping everything down to the bare essentials. Place your motherboard on a wooden table or something of that sort, away from materials that carry static electricity. Have the CPU, 1 stick of RAM, and Video card installed, and all the power connectors from the PSU. Also, you'll need your case sitting right next to all of this, because you will need to hook up the power switch. If it turns on when everything is outside of the case, that means there was a wire or a contact of the motherboard that was making connection with a piece of metal from the case, or another ground point.

Second thing I can think of is that your PSU died.

 

[cjbee]

Sounds like you've got a short to me.

I would start by removing EVERYTHING from the case and stripping everything down to the bare essentials. Place your motherboard on a wooden table or something of that sort, away from materials that carry static electricity. Have the CPU, 1 stick of RAM, and Video card installed, and all the power connectors from the PSU. Also, you'll need your case sitting right next to all of this, because you will need to hook up the power switch. If it turns on when everything is outside of the case, that means there was a wire or a contact of the motherboard that was making connection with a piece of metal from the case, or another ground point.

Second thing I can think of is that your PSU died.

Thanks for the reply...and you were right...it was a short -- but not of the usual suspects.

After a whole day of messing around and swapping my parts in and out with my local computer store's stuff to no avail, I packed all my gear back into my case and wired it all back for the car ride home. Long story short...upon repacking, I noticed that the SATA cable coming from the front panel eSATA port was all bunched up and slightly tangled underneath my empty drive bays -- seemingly normal, considering I have never had this cable hooked up and thus have just kept it tucked away -- but I unraveled it and noticed that a tiny length of the plastic conduit along the cable had been stripped away. This must have been interfering with my case's power switch lead, which makes sense since my case was the only common denominator throughout the whole diagnostic process. So, I straightened the SATA cable, taped it up, and voila...computer booted just fine.

It all seems a little curious though...maybe I did something different or moved something else on that final rebuild...needless to say, I'm gonna be closely monitoring it but I am happy to have a working rig again. Will update the thread *if* necessary.

Phew.