Question PC keeps shutting down unless I press motherboard's start button ?

[SethSlax]

This has been plaguing me for a while, to the point where my PC has been sitting dead for about 4 months.

So about 75% of the time, turning on my PC will result in it shutting off within a second or two, then it will not respond at all to the power button.
The MB has a Start button on it, and pressing it twice will boot everything up normally (sometimes that doesn't work either).
I tested every part by running the system with it taken out. Still happens.

I thought it was the PSU, so I bought a new one. That worked for a day before the shutdowns happened again.

Running it barebones with nothing but the MB, CPU (won't turn on without it), and liquid cooling still causes the same issue.
I thought maybe the pump gave out but I can feel it pumping while it's on.

While it's running barebones (by hitting the Start button twice), nothing is overheating in the BIOS, nothing has ever been overclocked, and the hardware hasn't been throttled.

System is about 5 years old, but here are the specs:

ASUS ROG Crosshair Hero VI
Ryzen 7 1800x
4 x G.Skill TridentZ 8GB RAM
MSI GeForce GTX 1060 6GB
Old PSU: Antec 900W
New PSU: Seasonic GX-1000
H100i Closed loop CPU cooler
Samsung 1TB SSD
Seagate 3TB HDD

Again, nothing overclocked, I've regularly cleaned everything, no QCodes when booting other than the regulars, no crash reports, nothing.

Anyone have any advice?

 

[Lutfij]

Welcome to the forums, newcomer!

5 years can degrade the innards of a PSU to the point where it might be failing. What is the model for your Antec unit? As for the Seasonic unit, do you have the Focus or the Prime range of the GX? BIOS version for your motherboard at the time of writing? I'd also try and power the system off of another wall outlet, taking it as far as powering the system at a friend or neighbor's house to rule out an issue with the wiring in your house.

 

[SethSlax]

Welcome to the forums, newcomer!

5 years can degrade the innards of a PSU to the point where it might be failing. What is the model for your Antec unit? As for the Seasonic unit, do you have the Focus or the Prime range of the GX? BIOS version for your motherboard at the time of writing? I'd also try and power the system off of another wall outlet, taking it as far as powering the system at a friend or neighbor's house to rule out an issue with the wiring in your house.

Thank you for the warm welcome! This site has helped me with countless issues for years now.

Thinking about it it's actually probably closer to 6 years old.
Antec is HCG-900 and the Seasonic is Focus GX-1000.
BIOS was 7901 when this started happening but I flashed it to 8101 to see if that would help to no effect.
Lastnight I had the thought that since it's been switched off and used considerably less the past year (new baby, ftw) maybe the CMOS battery was dying, so I replaced it with a fresh one to no avail.

I never would have thought about a different outlet! I was so concerned that it was the PC itself.
I'm running it on a different outlet now, and it seems to be staying powered on after several hard-hard resets (switching off the PSU and taking out the power cable until the MB drains all of the residual power). I'll keep you posted if it happens again.

I'm skeptical though, as it seems to get better before getting worse again. When it started, I took everything out, cleaned it meticulously, reapplied new thermal grease to the GPU and CPU, and it worked without issue for about a week before shutting down every time.
It just puzzles me that it'll shut down if I power it on with the external power button, but the MB Start button seems to get it running steady (at least for a little while). Thank you for the suggestions!

 

[SethSlax]

Welcome to the forums, newcomer!

5 years can degrade the innards of a PSU to the point where it might be failing. What is the model for your Antec unit? As for the Seasonic unit, do you have the Focus or the Prime range of the GX? BIOS version for your motherboard at the time of writing? I'd also try and power the system off of another wall outlet, taking it as far as powering the system at a friend or neighbor's house to rule out an issue with the wiring in your house.

So it's not the PSU. After some testing, everything was going ok for a bit. I let the system stay in for an hour or so at the BIOS screen and everything stayed on. Turned it off, back on and the issue happened again.
Same thing, if I turn it on via the Start button on the MB it powers on ok and is stable for a bit, but then dies randomly. Otherwise it dies 8/10 times powering it on.
Returning the PSU tomorrow. Starting to think it might be the MB. I hope to hell its not the CPU (still expensive as hell to replace!). Any other ideas? Thank you for the suggestions so far.