Question A770 In New Build Worked Till It Didn't, Now It's All Dead!

Feb 5, 2023
Replaced my 5-year old PC with a new build this weekend with parts from MC:
  • i5-13600k
  • 32Gb of G.Skill DDR4 RAM
  • Peerless Assassin 120 Cooler
  • ....and an Intel a770 GPU
On Saturday I put everything together, flashed the BIOS via a thumb drive prior to booting to get it ready for the processor, turned it on and immediately went into the BIOS to ensure Resizable BAR was enabled, and then I installed Win11 via a different thumb drive. Install went fine, system was stable, Win11 boots up. I go to bed because it's late at this point.

Sunday morning the system boots up fine, I start downloading software, etc. I also load a single game via Steam. The game loads smoothly, runs quickly, CPU and GPU temps are looking good! There is some display weirdness (random red pixels all over the screen like a vampire snow day) but that's to be expected with a new GPU, right? I play for 15 minutes and then life gets in the way. I leave the game running go out to run errands. When I get back the system has hanged, so I hard reboot and all is well. I end up playing for maybe an hour more, temps still look good the entire time, and then the display cuts out completely - no signal. I have headphone on and the game is still running in the background, so I plug and unplug the HDMI cable. Fixes it, but only for a few minutes. My workaround eventually stops working when the system hangs completely.

Hard reboot loads windows - I can hear the startup sounds - but no signal from HDMI. Putting the HDMI cable into the mobo HDMI slot doesn't work. After a few more reboots we're not even making it to Win11 anymore. I reseat the GPU and the RAM, check all the PSU connections, nothing works. Went as far as to remove the GPU entirely, but still when I try to boot it just hangs with the VGA and BOOT lights lit on the mobo.
Not sure where to go from here. Any advice is appreciated - thank you!