Question PC sometimes fails to start after pressing power button using HX750


Jan 9, 2013
I'm having an issue with my PC, and its really head-scratching to figure out what is causing my issue.
On average, once a week, my computer sometimes doesn't start after pressing the PC case power button.
It's not major, but it is concerning and I am trying to figure out what the issue is.

Motherboard: ROG Strix Z390-E, BIOS (v.1401)
PSU: Corsair HX750, Model number: SKU CP-9020137 , not sure of the amps.
GPU: Gigabyte GeForce RTX 2080 super gaming OC white 8G
CPU: i7-9700K 3.60GHz, unparked, overclocked to 4.9GHz
RAM: Vengeance LPX C16 2x8GB DDR4 2666MHz black, no overclock
Vengeance LPX C16 2x8GB DDR4 2666MHz white, no overclock
Operating System: Windows 10 Version 1909
M.2: Intel 660p
Monitor: AGON AOC AG352UCG6 3440x1440 @ 120Hz with G-sync enabled
Case: Corsair Carbide Series 400C (around 2017 model)

What happens:
  • The power cable is plugged in and the PSU switch is ON.
  • Motherboard RGB lights are ON, indicating it has power.
  • I press the PC case power button once. The PC case button does not light up.
  • There is a sudden click from inside the PC. No fans spin. No additional motherboard light indicators go on.
  • If I press the power button again nothing happens. The motherboard RBG lighting is still on.

  • Note: sometimes when I turn my PC on and don't encounter the issue, the power button light goes on, PC fans start spinning. Then the PC turns itself off for a second (start button light goes off), and then back on again and boots correctly with no issue.
When the issue happens, it seems to just be a matter of time until my computer correctly turns on and boots up.
It has started happening around a month ago, I have not made any major changes to my PC, I've upgraded to an M.2 drive, but the issue has occurred before that. Eight months ago I upgraded my PSU from an older HX750 model to their new model (silver and black SKU CP-9020137) due to fan noise issues. So far it has been flawless.

Things I have tried far:
  • Changing the power cable. Sometimes this allowed my PC to start, but the issue still arose on the different cable.
  • Using a different electrical outlet (my PC power cable is plugged directly into an electrical outlet). Sometimes this allowed my PC to start, but the issue still arose on a different socket.
  • I've checked to see if the PC case button is the issue by re-wiring the reset button as the power button. I would press it, hear a click as described above, and the PC won't start.
  • On the Z390-E motherboard there is a MemOK!_II switch, I have turned this OFF. No difference happened.
  • I have checked all cable connections by re-plugging everything. It all seems in order.
Things I am considering trying when the issue pops up again:
  • Reset Cmos by removing the motherboards button battery whilst the PC is off for 20 seconds. I would like to save my profiles beforehand though.
  • Trying to use my old model HX750 24-pin ATX cables.
  • Trying a PSU short circuit test?
  • Holding the power button down for a while to clear the static electricity?
  • Update BIOS?
  • Change HX750 Rail settings switch? It's currently on factor default.
I have found a similar article from a while back, but my PSU shouldn't be completely broken as I'm currently using my PC to write this.

I can take screenshots of any BIOS configs if need, just let me know!
Thanks a lot for having taken the time to read through this. I really appreciate it!


Edit: Added more information
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