Question PC won't turn on after shutdown or sleep mode ?

Oct 12, 2021
Hi Everyone! Long time lurker, first time poster.

The problem is pretty much as the title describes. I've had my PC with it's current parts for over a year now and the problem just started happening. What happens is after I turn off the PC or put it to sleep, it wont turn on if I press the case power button OR short the mobo pins.

Things that I've done that have turned it on again have been:

  • Unplugging the power cable from the back and draining CMOS (and replacing it) and waiting 30 minutes to an hour before trying to turn it back on.
  • Flipping the PSU switch at the back of the PSU repeatedly and spamming the case button until it turns on randomly (hit or miss)
  • Lastly, I replaced the mobo with a Gigabyte Aorus Ultra Z590 as I thought the issue was a faulty capacitor on the last mobo which seemed to fix the issue for a day before the same problem arised again. (11 Oct)
I've just bought a new PSU to hopefully fix it once and for all but I'm hoping that you guys who are much smarter than me can maybe pick up something I've missed.

Todays (12 Oct) problem/issue was a bit weird - As usual when I went to turn on my PC in the morning it wouldn't turn on but after unplugging PSU cable at the back and flipping the switch, the PC turned on instantly (I didn't press the case button) and then it turned off by itself and turned on again by itself. A few minutes later it finally showed the motherboard bios screen and booted into windows normally.

There is no issues with temps, freezing, stuttering or anything of any kind once it turns on but its just turning it on that is really frustrating.

PC Specs are as listed:

CPU: i9 10900k (stock)
Mobo: previous part MSI MAG Z490 Tomahawk
new part Gigabyte Aorus Ultra Z590
Ram: T-Force Delta 3200 Mhz 32GB (4x8)
GPU: RTX 3080
Fans: LianLi Unifans
PSU: BeQuiet StraightPower 11 850W
SSD: Kingston A2000 1TB and Samsung 850 Evo 240GB and WD 1TB HDD

Everything is watercooled with EK and Bykski fittings.

Many, many thanks in advance to anyone that takes the time out of their day to respond/help.
Oct 12, 2021
Hey Greeko85! I haven't gotten to replacing the PSU as I've just bought it today. I got the Corsair RMx 750W (Tier A on the PSUCultist List). Current one in the system is the BeQuiet StraightPower 11 850W.