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What I am about to describe happens only sometimes. I would say in about 10% of the cases.

I have a system with a dual boot, with Windows 10 and Ubuntu. And in both systems when I decide to shutdown the computer, everything works as expected and the system shuts down completely. But SOMETIMES after 2 seconds of the PC being off, it turns itself again, kinda like if the signal that was sent to the PC was not the shutdown but the reboot.

When I do "Suspend" in Ubuntu, it is even worse! The machine goes to suspend state, but then it tries to boot itself up and after 1 second it fails and shuts down again... and tries to reboot itself again! And the loop continues without end! I actually have to take off the power chord for half a minute if I want to be able to reboot my computer, when this happens.

If this is something that happens with both OS, then it cannot be a problem with the softwre in itself.

Why could this be happening?

My motherboard is an ASUS P7H55-M PRO. These are the specs.

Enrique Moreno Tent
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  • Check capacitors on your motherboard (and inside the PSU maybe). There are many symptoms a [swollen/leaking capacitor](https://www.google.pl/search?q=swollen+capacitor) may manifest itself with. I'm not sure if such rebooting may be the one of them but examining the hardware wouldn't hurt. Replacing a bad capacitor at home is possible if you can solder and have steady hands. – Kamil Maciorowski Nov 20 '17 at 08:23
  • Sorry but I am not ever sure what a "capacitor" is... – Enrique Moreno Tent Nov 20 '17 at 14:52
  • [Those little "barrels"](https://en.wikipedia.org/wiki/Aluminum_electrolytic_capacitor) on your motherboard. Healthy ones look [like this](https://upload.wikimedia.org/wikipedia/commons/thumb/2/26/Elkosobrust.jpg/737px-Elkosobrust.jpg), malfunctioning may look [like this](https://upload.wikimedia.org/wikipedia/commons/f/f5/Al-Elko-bad-caps-Wiki-07-02-17.jpg). – Kamil Maciorowski Nov 20 '17 at 15:25
  • I will take a look to see if they look weird, but are you suggesting that if that is the case, I should change my motherboard? or just get it repaired manually? – Enrique Moreno Tent Nov 20 '17 at 16:54
  • Have you seen [this](https://superuser.com/questions/923393/computer-reboots-seconds-after-shutdown)? – user Nov 21 '17 at 23:17
  • And take a look at [this](https://superuser.com/questions/62798/my-computer-reboots-when-i-tell-it-to-shutdown) too. – user Nov 21 '17 at 23:26

6 Answers6

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The problem may be in your power button. I suggest you to disconnect it and check whether the problem persists. To start up the PC without it you'll need to short the pins where the power button is connected now. Most people do it using a screwdriver, search the Internet if you're not sure how to do it.

user
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This could be the case of a remaining static charge on the mainboard, or a wrongly connected pin of the power-switch cables to the mainboard. try to find the power-switch connection, disconnect and connect again

Rockbar
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    Can you give me any pointer as to what I should be looking for exactly? Some sort of image or hint on what it could be? – Enrique Moreno Tent Nov 17 '17 at 21:25
  • if I were you, i would load the mainboard scheme from the manufacturer homepage, e.g. Asus, gigabyte, whatever. First locate there and then lookup on the mainboard – Rockbar Nov 18 '17 at 06:18
  • Tried that and it did not work. In any case, remaining static energy would not cause me this issue for a whole year, as it has been, no? – Enrique Moreno Tent Nov 18 '17 at 11:31
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See your poweron options in bios. Maybe there is something that triggers the PC wakeup.

Try to look deeper in "Ai Tweaker" enter image description here

and "Power" tabs in BIOS enter image description here enter image description here

also maybe you need to set another Voltage values, try making them lower or higher, but don't max out.

styrofoam fly
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user1448914
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This sounds like a faulty power unit to me. I'd recommend pulling it out and taking it to a local PC repair shop to get it tested. Most places will offer this for free, but you can always call ahead to ask. Feel free to follow up if that turns out not to be the issue, I'll help where I can.

jcam3
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Had an issue like that some years ago. Turned out it was the Ethernet cable/router. Try to power down the computer with the ethernet physically disconnected to see if the problem persists.

If it does not fix it, I'd suggest removing all peripherals: mouse, keyboard, audio jacks, monitor cable, and seeing if that solves the problem. If that solves it, reconnecting them progressively should yield the guilty appliance.

darmual
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There is an option in BIOS to auto-power on a PC, but even if it is configured to auto-power on, it should never experience the on-off loop. This is very unlikely a BIOS configuration issue.

It's possible but highly unlikely to be a power button issue. You didn't provide any details whether when the on-off loop happens, that unplugging and replugging actually successfully stop the loop. If the on-off loop still happens even after unplugging and replugging, you know it's not the power button. And that happened to my own PC.

It's probably not a dual-boot / software issue too. I used to have it on single-boot Windows system.

I don't have a particular answer but I'll try my best, if you follow through a particular experience I had, to lead to a likely problem with your mounting of the motherboard, and arrangement of hardware in the PC casing.

My experience

So on my older system, if I remember correctly, once the PC had shut down, after a few seconds the PC would automatically turn on (i.e. the fans would spin up and the motherboard LEDs, power LEDs will turn on) for about 5 seconds and then the system would completely turn off (fans and LEDs off). Like you said, the turning on and turning off would repeat endlessly.

I don't remember exactly solving the issue, but whenever the auto-turn-on happened, I'll hold down the power button for several seconds, which actually forces the system's power supply to shut down by most BIOS'es (unless specifically configured not to). This sometimes successfully made it stop auto-turning-on; but when it failed I would have to turn off the PSU's switch or the plug's switch, then hold down the power for a several seconds - in order to drain out the capacitors of any remaining charge. Then turn the PSU's / plug's switch on again and that would sometimes fix the problem; but it was when it didn't that actually provides a clue to the cause: Turning the PSU / plug switch back on, the PC turns itself on automatically, going back into the on-off loop.

If your issue is not the same up to this point, then forget about my answer. If not, continue reading.

The fact that we drained the motherboard's capacitors of charge when the mains was off should reset them, so that when the PSU / main's switch is turned on, the PC should not turn on itself automatically; But does in on-off loop. Which leads us to some shorting happening in the PC case.

Possible fixes that worked for me

The first thing I would do, is to ensure that the motherboard's mounting screws are not too tight. If you have clunky hardware (like big GPUs, CPU heatsinks), it can cause the motherboard to bend ever so slightly so that part of the motherboard touches the casing. That contact between the motherboard and the case can lead to a electric short which can trigger a pc go into that crazy loop.

The second thing is to check to make sure all hardware components are not touching each other excessively. Keep the inside of the casing tidy.

When I did so, the frequency of this on-off loop drastically fell. Although I didn't completely solve the problem, it mostly fixed it for me, for some time before it began to happen again more often. Over time the components in the PC shift slightly from minor knocks or moving of the PC casing. So it would be great to have a good casing that would not be so susceptible to such issues.

L. J.
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