Rog Strix Z790-A gaming WiFi II Win 11 Pro hard crashes, then won't boot

[soultech]

I built a recording studio PC last may. First go round I used

• ASUS ROG Maximus Z790 Formula ATX mother board, Intel Core i9-4900K
• Corsair Dominator Titanium RGB DDR5 RAM 96GB (2x48GB) DDR5 6600MHz CL32
• Corsair Professional Series AX 1200 Watt ATX/EPS Modular 80 PLUS Gold (AX1200) power supply
• Crucial New 2024 T705 4TB PCIe Gen5 NVMe M.2 SSD
• ASUS ROG Ryujin II 360 RGB all-in-one liquid CPU cooler
• No overclocking at all, ASUS/Intel BIOS defaults

The build went great and the system ran from May - Oct 2024 without any issues. In Oct it started randomly hard-crashing and every time it happened the system would not boot back up. When I press the power button on the case, the fans light up and the CPU cooler starts to show its image, but in less than 1 second it shuts down. I could leave it off for days and it would not boot back up, same behavior.  If I completely cut the power to the PC and leave it off for a day, then reconnect it and turn on the PC it POSTs and boots up to Windows without any complaints. Then it will randomly crash again and the process repeats. 

In Oct I installed the BIOS ver 1703 (10/18/2024)

In Dec I flashed in the BIOS ver 1801 (12/06/2024)

In late Dec I reached a point where nothing I did made a difference, it would not boot at all. Just then <1 sec power up and off sequence.

End of Dec I warrantied my CPU with Intel and got a new replacement. I installed it and nothing changed. Still would not boot at all.

So I stuck the CPU in another PC I have an it worked fine. I put the i7 out of the PC in the crash PC and still nothing.

I bought a new Asus ROG Strix Z790-A Gaming Wifi II motherboard. Swapped everything in and flashed the BIOS to 1801 and everything worked great with the i7-4700 in it. Its been running for about 10 days and then Saturday night while I was recording it hard-crashed and the boot up problems started again.

I disconnected power and left it alone for a couple days, then powered it back up today and it booted right up. About 10 minutes later while I was browsing the internet it crashed again.

DRAM sticks are in A2/B2. I tried moving them to A1/B1 but it made no difference.

I'm so bummed. Can anyone help me troubleshoot? TIA!!!

[soultech]

I'm starting to suspect the power supply. I don't know how to test it though.

[soultech · Accepted solution]

I solved this, for anyone coming across this thread in the future. I had pushed the "clear CMOS" button while the computer had power to the motherboard. Deep in the manual there's a warning that states something to the effect of "never hit the Clear CMOS button while the motherboard has power, the computer will not boot following that fail".  

The solution if you do this is

• unplug the computer
• remove the CMOS battery for 30-60 seconds to let all the motherboard capacitors drain of all power
• re-install the CMOS battery
• while the plug is still removed, hit the Clear CMOS button
• I hit mine like 3 different ways, quick click, wait a bit then hold it down for a few seconds, etc... 
• plug the computer back in
• turn it on
• Reset the BIOS to factory settings

My baby booted right back up finally!

[soultech]

The PC wasn't turned on when I hit the button btw, I just didn't know I had to unplug it before hitting Clear CMOS