PC won't turn on when case button is pressed

Had a previous issue which is located here:

Random freezes or BSODs (In windows drivers) - Windows 10 Forums

To tldr it was fixed by displaying all startup items and services.

Had a freeze today and after that when I turned the PC off (via case switch) it wouldn't turn back on again.
I tried different sockets and leads to no avail.
I performed the paperclip test which worked, and all voltages where ok (blue was -11.36 but thats been low for a while).
I then plugged everything back in and moved my attention to the power case button, and tested its connector to the motherboard and a voltage was present when and only when the power button was pressed.
I then tested the grey "POWER_OK" signal cable, which never changed when the power button was pressed, however this displayed a 5.1v signal when doing the paper clip test.
So then I tested the green "power on" signal cable, which showed 3.525v constantly, even when the power button was pressed, it was my understanding this should drop down to 0v, or at least drop when the power button is pressed?

If all my tests knowledge and assumptions are correct this means there is an issue with the motherboard from where it receives the power button signal to the 24 pin connector? If so what do I do next?

Thanks in advance for any help!

It could be a power supply issue. Nearly all, if not all, computers are now the ATX variety where the power supply connects to the motherboard and the I|O switch connects to the motherboard, pressing the switch sends a signal to the motherboard which tells the power supply to go to work. The older AT computers had the power switch connected directly to the power supply and turning the PS on then woke up the motherboard and peripherals.

Tracking down which part of the power chain has failed can be problematic but one thing that can be done [and I've had success with] is to remove all power [unplug the cord], press the I|O switch or wait a minute for residual power to drain from the motherboard then open the case and locate the 20/24 pin plug on the motherboard. It's got a latch and sometimes unplugging it 'normalizes' things.

As mentioned I have tracked down and found that the green power on cable within the 24 pin is not changing voltage on pressing the case power button, but I know the button is sending the signal so I believe I have found the problem, but not a solution. I will look at this latch in the morning however I have unplugged and replugged to no avail.

The PSU is probably OK if it passes the paperclip test and the voltages are OK. Disconnect the PC On switch motherboard connector and try shorting those pins on the motherboard. If the PC powers on then you have faulty On switch, else it's likely you have motherboard problems probably needing a new motherboard (and CPu & memory?)

How exactly would I go about shorting out the pins? If that doesn't work are there any other tests or fixes, as a motherboard isnt the cheapest or easiest to replace?

buncieboy said:

How exactly would I go about shorting out the pins? If that doesn't work are there any other tests or fixes, as a motherboard isnt the cheapest or easiest to replace?

Just use one of the motherboard jumpers or very carefully short the pins with a suitable size screwdriver.

If that works then there is a fault in your On button or connecting lead. If not, suspect your motherboard. I would consult Gigabyte support since I've found them very helpful even when well out of warranty. Also check out some motherboard forums as listed below.

https://forums.overclockers.co.uk/fo...otherboards.2/
https://forums.tweaktown.com/gigabyte/
http://www.tomshardware.co.uk/forum/...e=motherboards

So I manage to fix it by removing and putting back in place the clock battery, not sure if this was the only cause and it is perfectly fixed but it now turns on!

buncieboy said:

So I manage to fix it by removing and putting back in place the clock battery, not sure if this was the only cause and it is perfectly fixed but it now turns on!

I'm pleased you found a solution - your BIOS may have been corrupted somehow which once happened to me after a power glitch. Removing the battery would reset the BIOS - check the settings are what you need. Did you check the battery voltage since it might be time for a new one? Mine normally last about 3 years. Also check if you have the latest BIOS for you motherboard.

buncieboy said:

So I manage to fix it by removing and putting back in place the clock battery, not sure if this was the only cause and it is perfectly fixed but it now turns on!

Doing this has the same effect as a reset of the MB BIOS. It would suggest that your freeze corrupted the BIOS settings in some way. There is often a jumper that you can use to do the same thing which is often quicker and easier than removing the CMOS battery.

So thats all good, except for the fact that I got another crash (BSOD but failed to dump) and then the PC struggled to boot again as seen in my last thread. I've attached the log collector as well as the monitoring software I had running, it was idle for about 5 hours before use to see if the PC was stable, this either shows it runs stable without usage, or leaving it idle for so long causes an issue. Either way ill attach it (along with the min max and avg values) so you can poke around, (Link here Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.) however I couldn't see anything obvious!