power button won't turn pc off

[licio]

Hey;

A few days ago I started having an intermittent problem, happens about every second time I start the computer.

When I turn the PC on from a shut down state, I hear it beeping like it always did, the mouse/keyboard/monitor light up normally. However, the lights on the mouse/keyboard shut down in a few seconds as if they had no power at all and the monitor goes into stand-by mode. All of this happens while all the PC's fans and LEDs are on.

When I try to press and hold the power button to shut it down, nothing happens. I need to turn the PSU power switch off to get any response from the PC.

Thanks in advance!

 

[photonboy]

https://www.memtest86.com/

To be clear, this happens with a complete, COLD shutdown (not Standby or Hibernate) and the startup problems happen before there's any booting into the Operating System?

That would indicate a HARDWARE PROBLEM. My top choices would be:
a) motherboard, or
b) power supply

At this point I would UNHOOK all drives and even the mouse. Have a MEMTEST86 USB stick created prior and run that to test the system memory. I doubt it's the system memory (i.e. DDR3/4) but this is a good test to figure out where and when the problems are happening.

Still problems?
a) remove video card and use the iGPU (connect monitor to motherboard) if that's an option
b) unhook the case POWER connection to the motherboard headers and (carefully) short the headers to turn on and off (I doubt this is an issue, but this is just in case there's some weird issue with the case power switch. never heard of one so it's only if stumped).

*At this point I'd look for a spare POWER SUPPLY to test.