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Cousin's PC will not turn on, trying to diagnose the cause.

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Cyber Akuma    1

Yeah, these are always fun since it could be just about any vital component and sometimes even non-vital ones that cause it. 
 
From what I recall, his specs are: 
OS: Windows 7 
CPU: i7-4770K 
PSU: Seasonic SS-760XP2 760W 
Motherboard: Asus Z97-PRO(Wi-Fi ac) 
GPU: GTX 770, don't recall the make. 
I don't remember the rest of the specs, but I don't think they are relevant to this. 
 
My cousin told me that his PC suddenly stopped working and would not turn on, he sent me this video: 
 
https://photos.google.com/share/AF1QipMxvP4qq5OpvC8sx66YJNFz9pBf2ZTpqBe4oYtK9NSQRApAaHOBmZeWvIUhT69-qw?key=cWZOaVJwTUswdDNrRWxyYkwzU21McE4yb0FENl9n
 
I went over to check, pressing the power button just made the PC attempt to power on for half a second, then shut off, and it would loop like this until you did a forced shutdown. 
 
The motherboard has a POST code display, but it would just show 00 on it, which leads me to believe that it's not even trying or getting able to POST before it shuts down. I really hope this means that the issue is likely something else and not the motherboard, especially since IIRC this model of motherboard can function in an emergency BIOS re-flash mode with nothing but a PSU and USB drive connected to it, not even a CPU. 
 
Normally I suspect the PSU in these cases since that has almost always been the case in my personal experience. I removed the GPU just to be safe and connected the HDMI port to the motherboard's internal video, there was no video signal detected. I tried making sure all the connections were not loose, use different cables or ports on the modular PSU for the necessary power connections, etc, nothing. Even stranger the motherboard/PSU seemed to be keeping power (there is an internal backlit power button on the motherboard for testing purposes that acts as the case power button, even with the PSU's physical switch set to off and the power cable unplugged from the wall this button was still lighting up, unplugging the ATX20 cable was the only thing that turned it off) even with the physical PSU switch off at times. Nothing was making a difference until I attempted to run it with the additional (I think it's called CPU power?) 8-port connector removed. I wasn't expecting it to turn on at all or just keep looping since that is a mandatory power connector, but instead it stayed on this time and the video even flickered. It still would not POST since from what I understand that is a mandatory connection in boards these days, but there was some different behavior at least. 
 
According to the PSU's manual all of the ports in that connector are just simply 12V, so I got a multimeter and tried testing them, but was surprised to find that they were all delivering 12V. I tried to use the multimeter on the ATX20 connector to see if anything there was delivering the incorrect or no voltage but could not get the probes to come in contact while it was plugged in. I tried unplugging the ATX20 connection and jumping the power-on pins..... but he didn't have anything on hand that I could use to jump it, the only insulated wire he had was speaker wire that was far too thick to go in the connectors. So we ordered a PSU tester, it's set to arrive on Tomorrow. 
 
And there is where I am right now. I am not sure what else to do if the PSU tester shows up as the PSU being fine, so I wanted to ask for advice, both on what could be the case and what else I can try if the PSU turns out to be fine. The next part I would suspect is the motherboard, but I am not aware of any real way to test that short of buying another motherboard and completely disassembling and reassembling the PC, plus if we can't get the same motherboard that likely means a Windows reinstall as well. 
 
Any advice or tips about this?

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+jnelsoninjax    11,789

Pull the CPU out and see what the POST code shows, remove all the RAM and again see what POST code you get. You already have done good on the power testing and GPU, I would look into the motherboard and see if you can locate the clear CMOS jumper,this should help you, honestly it sounds like a corrupted CMOS setting, and clearing it is an ideal method for diagnosing the issue. I'll go ahead and call @DevTech here, he is very helpful in these situations.

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sc302    1,722

What kind of cooler is on it?  Is it a screw down or clamp down?   Try removing some pressure if you can. I have found with asus boards that if the cooler is too tight it can create a break in the memory channels causing a 00 code. A fix is to loosen the cpu heat sink. I have a aio Corsair water cooler which has 4 thumb screws and this happened on mine. Just need it a little past when you start to feel pressure on the screws, don’t need to make it as tight as you can. It has to make contact with the cpu, the heat sink/water block does not hold the cpu in place, cranking down does not increase cooling capability. 

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Cyber Akuma    1

IIRC, the cooler is screw-down. Would that really cause the issue if the system was running fine for years?

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sc302    1,722

it could.  Heat cycles can create micro cracks. 

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goretsky    1,030

Hello,

 

Just to verify, the UPS that the computer is plugged into has no problems?  Have you tried just plugging the PC directly into the wall (possibly an outlet on a different circuit) just to rule out it being the problem?

 

Regards,

 

Aryeh Goretsky

 

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Cyber Akuma    1

Yeah, just plugging it into the wall directly is the first thing I tried to make sure it wasn't the UPS.

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CyberChief    2

Not trying to be funny, but does the computer beep when turned on? I had a similar situation and the problem was a bad memory strip. If the computer does beep, how many times does it do this? It could be something in the bios or something may have gone bad on the motherboard. I hope you get this resolved.

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Cyber Akuma    1

No, beeps, no. Like I said the motherboard does have a digital display to show POST codes, but it just says 00.

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+jnelsoninjax    11,789
12 hours ago, Cyber Akuma said:

No, beeps, no. Like I said the motherboard does have a digital display to show POST codes, but it just says 00.

According to the motherboard manual, code 00 is not used, which is odd since it is showing it, maybe it's a D0? That would indicate a CPU initialization error, which would make a bit more sense in this situation. 

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