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I've ran into a issue with my computer that it does no longer reach POST, but simply powers on for a fraction of a second and powers off. But this is not always, some times it boots just normally and it works as it should, no issues with not enough power or anything. But as soon as I turn it of, I can not turn it back on, but then again at some random point it just powers up again, and resumes normal operation.

If I disconnect the 8pin ATX connector from the motherboard, it powers up, fans and disks spinning normally until I power it off again. So this problem only happens when ATX is connected, which seems odd, I normally always saw this kind of an error if ATX was not connected, but here it's the exact opposite.

It also does not emit any sound on the buzzer, except the normal beep, when it powers up normally. I have already tried:

  • Remove graphics card
  • Remove one and/or all RAM sticks
  • Disconnect everything non-essential, even hard drives
  • Clear CMOS

I have not yet tried to remove all components and tried to boot everything outside of the case, because I did not have the time to disassemble and bleed the water loop. However, I can confirm that nothing is stuck underneath the motherboard, not is any of those brass raisers touching the board where it should not.

Specs:

  • Gigabyte GA-970A-UD3

  • AMD FX6300

  • ATI HD7850

I think this should be enough for this issue.

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Without the 8pin connector it powers up, but nothings working, because the CPU does not get power, but everything else is powered up. –  tam Jun 9 at 8:59
    
I don't even come to POST with such behavior, but when it powers up normally, once in 300 tries, then there are no errors, anywhere, not on linux, not on windows, not stressing it with prime95, nor stressing the graphics card. Yes I plan to remove everything, and try to run it outside of the case to see if it helps anything. –  tam Jun 9 at 9:08
2  
IMO you need to test it all properly. Meaning, and I assume you don't have spare boards/CPU etc, taking it to a shop so they can diagnose it. As it currently stands, it's just too broad really. –  Dave Jun 9 at 9:20
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Seems like your PSU is dying. I agree with @DaveRook : take it to a shop. –  harrymc Jun 9 at 9:28
    
I have never took any of my PCs to a shop, and I don't intend to bring this one. :) I'll just start swapping out parts until I find the culprit. First on the list is re-seat the cpu and swap the psu, then, the motherboard, if not, try to find a spare cpu. –  tam Jun 9 at 9:43

2 Answers 2

Inspect motherboard capacitors, especially ones located near the power section (usually located around CPU). They tend to fail after some time (like 5 or 6 years, possibly faster if you have a cheap PSU). You'll identify bad capacitors by bulging, usually connected with small amounts of electrolyte on top. (some photos here)

Replacing capacitors is possible, but requires some soldering iron skills. Motherboard replacement is usually the best solution.

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Are those the little round "thingies" seen on this picture? key.ru/images/cms/imgwatermark/… If they are, they are all intact, already checked them. But AFAIK, if a capacitator is blown, the computer will not ever boot anymore, but mine does, from time to time, or is it not so? –  tam Jun 9 at 9:18
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Yes, these thingies are capacitors. They don't just break instantly, instead they slowly degrade. Sometimes you can have few of them slightly damaged and everything will still work. Booting problems like yours are typical for failing capacitors. –  gronostaj Jun 9 at 10:12
    
I've seen blown capacitators, and know their effects, I'm just amazed, or will be amazed if this is the issue, because this system is under 1 year old. Well, I cleaned my CPU with 70% alcohol, but I've done this multiple times, so I doubt that alcohol could kill the cpu, or could it? –  tam Jun 9 at 10:19
    
Alcohol shouldn't damage it. You could try using another PSU to make sure this one is fine too. –  gronostaj Jun 9 at 10:36

I have solved the issue. After close, cm by cm inspection of the motherboard I found a liquid stain on some chips, pretty small stain, at first, as I am running liquid cooling, I thought it was the coolant, but since it didn't have any color after wiping clean, I came to conclusion that it could have only been sweat, and I did sweat alot when I was re-assembling my build. After wiping it still didn't work, but after some brain storming I remembered I had alcohol, so I wiped up with alcohol, and let it dry for a couple of hours, and everything is working just ok.

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