PC doesn't always power on or stays powered on after windows has shutdown

[Adamz946]

Hi all, have been troubleshooting an issue with a PC over the past few days and I've pretty much exhausted what I can so reaching out to see if I'm forgetting anything obvious.

 

Original Issue

PC shut off randomly one day and since then it would turn on and work fine for up to 5 minutes and would then switch off. You couldn't switch it back on straight away and would have to wait 5-30 minutes even if power was disconnected.

 

I started a process of elimination and started swapping parts out, primarily the PSU, CPU, GPU and RAM. Briefly tested all components in another machine and they seemed fine and everything was also tested on a bench in-case the case was shorting out the board somewhere. I got to the stage where the motherboard was the only original part whilst using other known working parts laying around or from working machines. So I made the dive to clear the CMOS and that was the end of that boards life, it no longer powered up or showed any sign of life, new CMOS battery was tried as well a new BIOS chip which was flashed with the appropriate BIOS.

 

So, replace the motherboard? Right? Well..

Everything seemed to check out fine when bench testing and re-assembling the PC with the original parts, surprisingly the new board picked up the RAID0 SSDs but that blue-screened so we figured it would be best to reinstall. Took some work but managed to do a clean install on a single SSD with a spare RAM stick and creating a 120GB partition on the SSD, I could then put the original RAM back in and extend the partition to use the entire 180GB drive. 

 

Current issue (and completely puzzled)

The PC works in every aspect except it doesn't turn off. You can use the power button to turn the machine on and you can restart from windows but if you shutdown from windows or hold the power button the PC doesn't actually turn off, all components remain powered on and the only way to cut power is with the PSU switch. After a shutdown from windows, you can press the power button and it will post/boot windows normally despite all components still being powered. I done a sanity check and plugged another known good PSU in and the PC wouldn't even boot, it would power off completely and back on continuously (like a motherboard does sometimes with new hardware when it's finding the best setting to post). To the best of my knowledge the replacement motherboard is a known working unit. I feel like testing another CPU/RAM etc with the replacement motherboard next just to be certain on that last point but will need to strip a working machine down so could be a job for the weekend.

 

Specs

i5 3570k

16GB DDR3 1866 Corsair Vengeance

2 x 180GB Intel SSDs

Reference GTX 1070Ti

Coolermaster 600W/Corsair 500W for testing

Original motherboard ASRock Z77 Extreme6

Replacement: Gigabyte GAZ68XP-UD4 (flashed to latest release BIOS for Ivy Bridge compatibility)

 

Thanks all for your time reading and open to any suggestions, obviously spending money on current gen parts isn't an option really. 

[Mad153]

Hi, 

This sounds like a bug in windows. Have you tried checking for updates?