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For over a month, I have come home from a Saturday 16-hour shift on Sunday morning to find that my computer won't turn on.

Every day of the week besides that one, the computer runs flawlessly. I assume that this happens because this is the longest stretch of time that my computer is not in use.

This problem shows itself no matter what my shut down method is.

  • I have shut down the computer each day and unplugged it from the surge protector. Same behavior.

  • I have shut down the computer and left it plugged into the surge protector all week. Same behavior.

  • I have left the computer in sleep mode ALL WEEK to come home on Sunday and find it OFF that morning and refusing to power up (I had to laugh and cry at that one).

When the problem happens, I've tried unplugging the machine from the surge and into an outlet. No luck.

I've tried plugging it into a completely different outlet, with and without a different surge protector. Nope.

I've dusted it out. Try again.

I've stripped the thing down to just one stick of RAM and the CPU and tried to start it. Nadda.

I've replaced the CMOS battery, three times, with three different batteries. Nice try, but still, FAIL.

In the end, I've found that I have to wait before the thing will listen to the power button. That takes around two hours.

I can tell that I'm getting close to a start-up when after many presses of the power button and flipping of the PSU switch, the CPU fan spins for a split second then stops.

I was able to duplicate the problem before work this afternoon by shutting down and then holding the power button (while PSU switch was OFF and power cord unplugged) for around 30 seconds.

System would not start after it was plugged back in and the power button pressed. I unplugged the machine, repeated the previous step, plugged it back in and pressed the power button. This machine turned on that time, BUT I'm expecting to have the same problem when I get him this morning.

I have a feeling that tha problem is my PSU or motherboard, but I'm looking for a second opinion and am frustrated because my PSU is strong (Corsair AX750 Gold) and my motherboard isn't awful (Asrock Pro4 Z77). And my machine is only about 3 years old. I'm not thrilled about replacing either.

Other info/confessions: - Previously ran a crossfire AMD 7970 and 7950 for a few months (overclocked for gaming / under-clocked for mining) - System now runs just the 7970 (over-clocked, no hangs, artifacts or driver crashes) - Two HDDs (Windows 8.1 and Ubuntu 14.04) - Mild overclock on CPU on stock Intel cooler because I'm a moron. No issues, temps are good for Ivy Bridge I5. - I'm a first time cat owner, and wonder if the little guy is secretly involved in this, so I'm including him as a variable.

  • "I have shut down the computer each day and unplugged it from the surge protector. Same behavior." Just to be sure: so when unplugged for some hours any day, it would still power on fine? (Except for the Sundays, of course, for which then the only difference would be that it was unplugged much longer?) – Arjan Mar 29 '15 at 9:06
  • Yes. The range this week was from 6-16 hours powered off and unplugged. The computer powered on with no issues up until my leaving for work this Saturday when I held the power button down for 30 seconds after having unplugged and shut down. Even accounting for usage spikes and less down time around Thursday to Saturday morning, powered down time still falls in above range. I tried the same power down tactic (unplugging and holding the power button down for 30 seconds) about 6 hours prior and was able to power the PC on with no issue. – Chall Rajni Mar 29 '15 at 10:25
  • You have a Biblical computer...on the seventh day it rested. :-) – fixer1234 Mar 29 '15 at 17:40
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Being unable to start after a prolonged power-off is a common sign of a capacitors going bad. I've seen this a lot during the Capacitor plague. Even though your MB\PSU are using mostly solid electrolyte ones, it's still possible for them to fail.

Personally, I'd start with swapping PSU, because it contains large non-solid electrolyte capacitors in primary circuit and smaller ones in secondary circuits:

Corsair AX750 80 Plus Gold

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Capacitors, PSU and a long list of other parts can cause these symptoms. Most just keep buying new parts until something works. However the fewer and informed first identify the defect before even disconnecting one wire or part.

Removing RAM, changing a battery, etc have no relationship to your symptoms. You computer contains a power controller that decides when its PSU can power on or off and when a CPU is permitted to operate. Power controller has many inputs including the power switch. Nothing else can do anything until the power controller permits it.

Your symptoms are classic of a power controller that refuses to power or that sees a defect and powers back off. Only way to have a useful answer requires a voltmeter, requested instructions, one minute of labor, and posting those resulting numbers here. Only then can a fewer who know this stuff say what is wrong, why, and what must be replaced. Only then would you be fixing the only defect on a first attempt.

Everyything in that list is so layman simple that even a junior high school student can do it. But without those numbers, the fewer who really know this stuff cannot provide any assistance. Your only other alternative is to keep replacing good parts on speculation until something works.

  • I've had this problem with my capacitors before, even though it's a relatively recent machine. Sometimes the power controller will fail to permit power-on when it detects that the capacitors are still charged; this can generally be overcome by flipping the PSU off by its hard switch (or unplugging it if it doesn't have one) and holding the power-on button down for about thirty seconds. They'll drain on their own, but this expedites it significantly. After flipping the PSU back on I can usually boot. I don't know about power issues where you are, but it makes sense on that regular schedule. – Michael Eric Oberlin Aug 4 '18 at 0:17

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