Machine shows no signs of power for up to 24 hours at a time.

[zccassell]

First off, I'd like to express my gratitude to this forum for the years of assistance it's provided me in my lurking. This is the first time I've experienced what seems to be an unidentifiable (for me, at least) hardware issue but I'm assuming the error lies with the motherboard or its close relatives. I'll jump into the specs and a little bit of history before explaining the issue.

Specs:
CPU: i7 2600k, purchased in 2011, has spent the majority of its uptime at a stable overclock of 4.6 GHz.
Cooling: Corsair H60 water cooling unit (as far as I recall)
Power Supply: Corsair AX750
Memory: 16GB Corsair DDR3, given to me by a friend during his upgrade back in 2013.
GPU: MSI GTX 970, installed as an upgrade around the time it came out last year.
Mobo: Asus P8P67 EVO

Now onto the issue, which is a complete absence of any power when I attempt to turn the machine on. A couple of nights ago, everything was running great like usual, I shut it down for the night but then decided to quickly boot it back up to access my girlfriend's email for her but there were no signs of life whatsoever. Not a failure to boot but a lack of power like I had forgotten to plug it in or was using a bad outlet.

The next morning the issue persisted and I decided to reinstall the RAM and GPU to no effect. I tried, to my limited knowledge, ensuring that no leads on the motherboard had been jostled out of place and that the power supply wasn't missing any connections. Nothing seemed out of place so this didn't work either. The following morning I plugged in the machine and it booted fine. I left it running all day for fear the issue might return, which it did last night when I powered down and checked to see if it would be able to power back on: it didn't.

I have neither cleaned, opened, nor moved this machine since it's moved to my new apartment within the last 6 months or so which is why I struggle to believe the the internal connections have been affected. Until now, the machine's been running great and although I haven't been running programs to monitor its temperatures, I have no reason to believe anything's being overheated.

My limited knowledge leads me to the assumption that this could possibly be as simple as the cmos battery failing. That's what I hope at least. Any help or opinions will be greatly appreciated. Thanks!

 

[smorizio]

if you have a volt meter check the power good line on the power supply and mb pin. if the power is out of spec your mb wont turn on. also look at your mb case if there a daughter card for the power switxh it could be failing or there a lose wire or bad on switch. another issue could be a bad cap in the power supply or the mb. the last could be a cpu chip that not all the way down in the cpu slot.

 

[Gallarian]

Have you tried moving the PC and plugging it to a different power outlet in your house? I had similar problem with my previous system and it turned out the be the outlet.

The fact that both situtions in your post describe your PC working for a time, and then not powering on shortly after shutting them down could suggest a temperature problem. Are all your temps normal before you shut down?

I would also try a different PSU power cable if youve got one.

 

[RealBeast]

A dead CMOS battery would not result in a total inability to power up, it would manifest by things like your clock being way off if the wall socket power was disrupted. Most other errors would give you something.

The most likely problem IMO sounds to be power related. It could be in the wiring to the motherboard power pins from the front power switch, test that by using a screwdriver to short the two pins briefly, which would power the machine up. I've seen a number of those, and that would be good news.

Check to see that you are not on a ground fault interrupt circuit where there is a bad GFI, unlikely but I've seen it.

It could be that the PSU is failing. You can disconnect the PSU and test it by trying the paperclip test a number of times to see if the PSU powers up. It involves shorting the green 20/24 pin connector wire with a black (ground wire) with a paperclip bent to reach the two.

I had a PSU die last month on a 2011 2600k build, although my symptoms were a little harder to point to the PSU, occasional random shutdowns when running games. Fortunately, I keep spare parts to test and had a new EVGA SuperNova P2 850 on hand from a Black Friday sale.