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I recently replaced my motherboard, processor, memory, and power supply. After powering up and running for approx. 3 minutes, the rig shuts down, like somebody pulled the cord out of the wall. It won't power back up either instantly. I have to wait a while before I can even turn it back on.

At first, I thought it was a heat issue. I powered it back on, went into the BIOS, and watched the CPU and chassis temperatures. They never went over 90 degrees Fahrenheit.

I'm using the on-board audio and video; no other components are hooked up aside from hard drives and dvd burners.

I'm thinking it's the power supply, but I'd like to get some ideas from the community as to what else it could be.

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my money is on the PSU being the culprit but you do realize that it even more guesswork for us than it is for you. you can swap the components to find out, we can't. :) – Molly7244 Aug 29 '09 at 2:35
I know swapping components is the best way to troubleshoot things, but this is my only home computer, and I don't really have extra components laying around. That's pretty much why I posted this, because I didn't have a spare PSU. – Aaron Daniels Aug 30 '09 at 2:22
up vote 2 down vote accepted

I seem to be using this link a lot lately, but anyway:

PSU calculator from newegg. Just pop your hardware into that and it should give you some idea as to whether or not the problem is your PSU.

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Well, I have a 400 Watt PSU, and the calc recommended is 416... – Aaron Daniels Aug 29 '09 at 2:47
I'd say this is the problem then... There's enough power to boot, but once everything kicks in, it's drawing too much power and the mobo shuts off again. – Matthew Scharley Aug 29 '09 at 3:12
I unhooked the optical drives and a hard drive, and it has booted and stayed running. I RMA'd the PSU and ordered a 800W one. Thanks again! – Aaron Daniels Aug 30 '09 at 2:20

Is it always ~3 minutes before it shuts down? If it is and you can leave it on in the BIOS for over 10 minutes (or a significantly longer time), I would go down the route of either heat or power. If it shuts down in BIOS as well, I would point to power, but it could mean other parts are faulty

If the motherboard is one of the new ones that comes with the high end ATI video built in, (and even if it isn't) it is possible that when Windows (or your OS of choice) is started, it suddenly produces excess heat. Watching the BIOS is great, but remember it is running at around .5% (or less) utilisation, that being said, ~30c is very low!

Power, the same goes really. If you have one of those energy meters, hook it up and you will see that when the OS is started, it sucks up a lot more energy.

Personally, I could be wrong, but I would point more to a under performing / inadequate PSU than heat, but I think it is one of the two.

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You say it's not heat but you only checked the CPU temperature.

What if the PSU was warming up and reached the point it was unable to deliver the needed power--from your comment to ThisTime it sounds like you're at the edge. So long as the power supply is too hot it can't deliver enough power and the board doesn't work.

Alternately, the PSU has an overtemp shutdown of it's own.

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I also vote heat. I would advise that you check one easy thing, though: do you have the thermal goop (of whatever flavor) properly applied between the CPU and the heat sink? That's the kind of thing that, at BIOS loads, might not register. However, the moment the OS is doing useful work, heat hits the thermal stops and the processor shuts down to save itself.

HWMonitor may give you some insight. I would advise that you start that up immediately after boot and watch the temperatures of CPU and memory in particular. If you're running at relative idle, you should see low-ish temperatures (about 40C = 104F). If you're seeing idle temperatures 10-20C degree hotter, I'd worry about your thermal solution.

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