Hi team, looking for some advice.

My PC was working fine this morning, and windows 11 (23H2) (Ryzen 5600G, B550 MB) wanted to do an update, so I clicked to restart, as you do.

When it rebooted, the PC hard froze on the bootup screen after a half turn of the boot logo. No response from Caps lock on the keyboard. Left it for 10 minutes with no change. After a couple of hard resets I got "Preparing Automatic Repair" for about 2 seconds before the PC rebooted.

Long story short, The PC will not boot any media that I've tried.  Here's a list of troubleshooting tasks I've undertaken:

• Created Win 11 USB boot media (freezes at same point in boot sequence)
• Created Rescatux boot media (Loads Grub interface, can choose boot options, default boot gives a few kernel messages then reboots. Failsafe mode spits out a bunch more kernel messages, then hard freezes)
• Checked that BIOS was displaying RAM and SSDs correctly
• Removed m2 and SATA SSDs
• Removed GPU (CPU has built in graphics)
• Removed all peripherals except fans and case buttons (incl. Front Audio, front USB 3.2 and Front USB2)
• Reseated RAM
• Tried two RAM sticks individually
• Tried different RAM slots
• Checked seating of PSU cables.
• Updated BIOS using Q-flash (succesfully)
• Reset CMOS
• loaded optimised defaults

No improvement. Same symptoms.

Given that I have the same problem booting from the SSD, USB windows media and USB linux rescue disk, this points towards a hardware fault, rather than software.

AFAICT, I'm down to CPU, Mobo and PSU.

Are there any troubleshooting tips that I've missed? I could reseat and redo thermal paste on CPU, but I don't have another PSU or mobo to try, so it's a bit tricky to narrow down any other potential hardware problems.

Hardware:

Gigagbyte B550 Aorus Elite AX v2 mobo

32GB G-Skill RAM (2x16)

Ryzen 5600G APU

Cooler Master 750w modular PSU