financial mistake - POSTS, runs 5 days straight and crysis at 165 fine, then won't boot after shutdown.

[SMKPIPES]

Hi there all.
Nightmare Dancase A4SFX build with an asetek 545.
Just got it running great after many issues. Ran it at idle for 5 days straight to download programs/steam and to test for heat build up in the case and fan bearing flex issues (trust me its been a problem). Temperatures where excellent. no issues.

Then rebooted to install all of the programs properly and played crysis at 165 no issues.
Shut it down to give it a rest. About an hour later went to boot again and no response. Leds on motherboard where still on indicating no issues with power from house to motherboard .
Thought this must be an easy fix because cable obstruction of the power button and 2 pin disconnection has been a common problem due to cable.management and it having no clips.
Opened it up and no cable obstruction button seems to be working fine on case and the little button board
Checked the 2 pin. Its definitely in the right place and is all the way in. Has a little flex on it though which has me worried but I remember being normal. Saw a little dust on the cable connector so I blew that out.
My thoughts so far -
1- Broken power io 2-pin on the mobo 2 - maybe still dust bridging power and ground on 2pin cable
3 - button board stuffed
4 - Power supply gone but I doubt it .
5 - optane somehow
Serious considered help would be much appreciated.
Cheers
atlas

Dan Case A4 v2 SFX Chassis
Asus Turbo Edition 1080 Ti
Intel i7 8700K Coffee Lake 3.7Ghz
Hyper X Fury Black Edition 2x16GB DDR4
ASUS Z370I ROG STRIX
Intel Optane 800P 118GB NVME M.2
Samsung 960 EVO 1TB NVME m.2
Seagate Barracuda 5TB ST5000LM000
Asetek 545LC
Philips 272S4LPJCB 27in QHD LED Monitor
Acer XB271HUA 27in WQHD G-Sync 165Hz
Silverstone SX650-G SFX 650 Watt

 

[smorizio]

check that the power/reset switches are on the right pins. pull both and then see if with a screw driver you can short the on pin to see if the mb starts. if nothing happens. pull the gpu and see if clearing the cmos the mb post with onboard video. if there no post there can be a dead short or bad power.

 

[SMKPIPES]

Here's the answer -
The button module on the board had been slightly pushed down onto the circuit board, creating approximately 1mm of clearance, allowing the power button to be pressed halfway but not actuated at the bottom of the switch. Hence no boot no matter how hard you press the button.
Fixed with tape and a peice of a small cable tie. Took a few goes to get the right amount of plastic between button and switch to allow it to move properly while still hitting the button. Took more goes to get it to stay in place due to lateral play in the button. It now works better than the original button .

Thanks to the guy that answered much appreciated that would've been my next step had I not discovered the button issue.