HTPC suddenly shutting down every 2 minutes overnight

DeadnightWarrior · February 27, 2021

I have an HTPC built with:

- AsRock B450M-HDV R4.0 mainboard
- Athlon 3000G APU

- 2 x GSkill Aegis 8GB DDR4 3000 RAM modules
- Silicon Power A55 256Gb SATA SSD
- LG BH16NS55 SATA Blu-ray drive

- Tacens AnimaII eco smart 500W SFX PSU ***
- Windows 10 Pro 20H2

Please note: motherboard, CPU and RAM are brand new, I bought them no more than 3 months ago. The CPU cooler is also quite new being only 4 months old.
The SSD is more than one year old but it actually sat unused until december 2020.
I haven't touched the AMD drivers since day one, they are still the exact same I installed when I built the PC.

This machine is ONLY used to play movies, TV and music, either from disc, files or live streaming. No gaming, no office work no overclocking. It's strictly a media player.
It had absolutely zero problems from the day it was built until today. Never had overheating or power issues either.

Then today I turn it on as usual and out of the blue, it freezes with a totally green screen; I push the reset swtich and from that moment on, it begins to shut down after a couple of minutes every time.
After some failed startups, I then try to access it via remote desktop, it works for two minutes and shuts down once again: I turn it back on and this time I hear 5 short beeps on boot.

As far I know, 5 beeps on an AsRock board means "no graphics card". The problem is, I have no graphics card as I'm using the Athlon's integrated GPU.

The only thing I could spot on Windows' event viewer was the classic "41 Kernel Power" error, which means all and nothing. Never had any time to dig deeper as the PC would shut down before I could.

What could it be?
PSU? Motherboard? CPU? Memory? Drivers?

Thank you for your help!

*** : Yes, I know it's not a great PSU; that being said, the 5 beeps at boot AND the freezing with green / blue screens could make me think of graphics issues, rather than power issues... I guess.