Computer boots for 3 seconds only to shut down

Quote:

Originally Posted by isamu 

Hello. Having a problem with my PC. I have an Intel processor Core i7 950 OC'ed to 4.0Ghz, Corsair H-80 cooler, NVIDIA GTX680 and Corsair TX-650 PSU.
When I boot my PC the mobo leds light up and the fans spin only for about 3 seconds then the machine shuts down. Doesn't even get to the beep. The night before, I had no problems. The Corsair H-80 keeps temps on this Core i7 CPU always fairly cool at around 50C and around 60-70C under heavy load.
Is this most likely a power supply problem? Someone elsewhere suggested removing the internal battery and resetting my CMOS, *before* buying a new PSU. Do you recommend this? Or is the PSU most likely the culprit of the problem?
Now for a disclaimer....
In the past, the PC HAS shut down after a couple seconds a few times before, but then it simply rebooted itself a second or two later, and when it did it back it would just boot Windows normally but revert back to its stock CPU clock speed. I would go into the bios and change it so that it goes back up to 4.0Ghz again and all was good. Are those previous incidents something that could have possibly led to this current malfunction?
Thinking of buying an Antec EarthWatts EA750 750W PSU at Frys tomorrow. Suggestions?

It sounds to me like a very unstable overclock.  I'm not speaking from experience, but I'm considering the fact that it's only doing it when it's overclocked.

I recommend reverting back to stock, and then overclocking again - but this time do it bit by bit until you get to 4.0 GHz, but running good stability tests in between each step.  I mean, always tweak the overclock so that your system can run Prime95 for 12 hours or more.

Quote:

Originally Posted by Empr1ze 

Maybe you have shorted your mobo.

If it were shorted, then wouldn't it only stay on for about a half a second as opposed to 3 whole seconds?

Quote:

Originally Posted by isamu 

Thanks for the replies guys. @ TwoCables...
This machine has been stable for over a year at 4.0Ghz overclock. Only incidents have been the ones like I mentioned above, where I turned it on, then it shut down, then quickly re-booted again with no problems except reverting back to stock speed. This time however, it's not rebooting on its own and simply stays off.
I did not OC it, the company(AVA-Direct) did. I do not know how to overclock a CPU, but a friend of mine does. I guess resetting the CMOS is probably an idea, but I wouldn't know where to start when going about re-OC'ing this intel chip.
My current power supply is a Corsair TX650 650 watt. About a year old and the PC has never shut down while in use before.

If someone else did the overclocking for you, then that, to me, is all the more reason to suspect that it wasn't done correctly.  When it comes to building a computer and overclocking it, I feel that the old saying always applies:  "If you want something done right, then you have to do it yourself".  To be honest with you, this stuff is actually pretty easy - otherwise I wouldn't have been able to do it (and I'm easily overwhelmed by even the simplest of tasks).

I'd say that the instability is now rearing its ugly head and now it's so unstable that it's not even functioning anymore.  If they had done a better job of making sure it was stable, then it would probably still be working right now, but this is the risk anyone takes when they have some outfit overclock their system for them.  After all, it's not their computer, so they don't truly care about it.  They just do it and say, "Here you go.  Enjoy".  Plus, 4.0 GHz is no small overclock for the i7-950, so it requires at least a few days of overclocking, testing, failing, tweaking, testing, failing, tweaking, testing, failing, etc. etc. etc.

So I say that you should revert the CPU back to stock and overclock it yourself.  Fortunately, you are on Overclock.net, so you are already an expert (because you have access to the combined knowledge of all of the experienced overclockers here).  I mean, sure you can have your friend help you, but Overclock.net is always a better place to go to seek help with this stuff.

I imagine one thing everyone will need to know is which motherboard you have, so do you know which one you have?  If not, there are ways to find out - some are easier than others, but some ways don't always work.

I'm done editing my last reply above.  You can read it now, I think I'm done adding things.  :)