So I built a computer for a friend around a month ago (specs listed below), had some minor wiring issues with getting the computer to start, specifically it would start up for under a second and shut down, but figured it out to be due to the CPU fan not being properly latched on. What is now happening is that the computer will simply shut down for no apparent reason, after as little as before even reaching the startup screen, to after running for 24 hours non-stop. To clarify, when I say shut down, there's no blue screen, no error report, and I have to reset the power supply each time to get the computer to start again.
So far it's gone through Ungine Heaven and FurMark to check the GPU and passed fine on high settings with the temp never going higher then 70.
Put the CPU through prime95 on each of the 3 presets (mind you only for an hour, so it possibly wasn't long enough?) with no errors.
I have NOT tried swapping power supplies with my personal computer (Corsair TX650), as I assumed that the brand new TX750 in my friend's computer wouldn't be failing already.
There was some loose, but plastic capped, wiring that seemed to be touching the underside of a SATA HDD, and possibly brushing against one of the fans, but the said wiring was specifically for the GPU.
All 4 fans are running just fine, but the CPU heatsink fan sounds a tad loud with it's whirring noise considering it's a stock AMD processor fan.
I've run virus scans with Kaspersky, Malwarebytes, and Spybot, all coming up with nothing.
That so far is what I've done, not a lot, but I'm currently not to sure as to what to check next...replace the thermal paste? triple check the CPU fan? Test the power supply? OS failure?
On a side note, I didn't purchase these parts, I'm an Intel & Nvidia fan myself, the friend had help from a sales rep at Canada Computers.
Stock AMD CPU fan
2x4GB Corsair Vengeance Ram
500 GB HDD
Nvidia Asus GTX 560 Ti
Your generic $20 optical drive
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To me, it really does sound like a PSU issue, I'd go ahead and try a PSU swap, see where you get. The lack of blue screen or shutdown notice is why I'm leaning that way.