Computer died after pressing reset button, DRAM Led stuck on

Question

yesterday after a long gaming session I decided to quit the game and my PC stuck at the exit screen, I couldn't move my mouse pointer, ctrl+alt+del didn't didn't work and out of frustration I decided to hit the reset button on the case. My monitor displayed a black screen but my PC didn't turn off, and even pressing the power button for long time didn't turn it off so eventually I turned off the power directly from the PSU (stupid choice, ikr).

From that moment on my PC won't reboot. Now the EZ debug led for DRAM is stuck on and the PC doesn't POST, my display doesn't receive any signal. I own an MSI BMG B550 Gaming Plus motherboard, and I'm now trying to diagnose what is failing. Things I tried:

1. I tested the RAM given the diagnostic LED that's turned on. I tried to leave one RAM stick at a time, I tried to swap their positions and so on but nothing worked. I tried putting both on another working PC and they work just fine.
2. I tried to reset CMOS, removing the battery from the motherboard for around 10-15 minutes, it didn't work.
3. I tried flashing a more recent version of the BIOS through the back button. It obviously didn't work
4. I disassembled my whole PC and assembled back in place to check for visible signs of burnt components or something like that, but I didn't see anything suspicious.

So now there are four possible causes left: my PSU (which is by the way almost 7 years old) died, but it doesn't seem the case cause I'd expect the PC to turn on and then shut down during POST (right?), or my motherboard died, but I don't know how to test for this... all the lights turn on fine and all the components seem to be correctly turned on: lights are on, fan are spinning and so on. Otherwise it could be the GPU (God I hope it isn't since it's an RTX 3070) or the CPU. How do I determine what the hell is going on?

TIA!

Answer 1

First of all: I don't think that you resetting or switching off your PC did cause any problem. It hung befor so whatever happened to your computer happened before you shut it off.

Shutting the PC down the hard way is not a big issue for the components. It can only be an issue for the OS or more precisely for the filesystem. The file system could be in an inconsistent state after an unclean shutdown. But modern operating systems on modern file systems (and for once I count recent versions of Windows in that category) can handle this gracefully on most cases.

But this is not your issue. Because your issue appears LONG before the OS even starts up!

So what could be wrong? Basically almost everything! You've done some good debuggying already so let's continue.

IT could be your power supply. And depending on how it failed it could display exactly that behaviour. Maybe it does not output the right voltage (check with a multimeter if possible). Maybe the voltage drops as soon as there is load. To reduce the load remove the graphics card (if you have graphics onboard, plug your monitor in there, otherwise just start without display). See, if the behavior changes. If you get another behaviour it's probably either the PSU or the GPU.

The next suspect would be the mainboard and especially the VRM around the CPU there since they are under a lot of stress on high load. Testing that is hard without parts to swap around.

I'd list the probability of failure of the components in this order:

1. PSU
2. Mainboard
3. GPU
4. RAM
5. CPU (except if you're overvolting it)

So it comes down to swapping out components in the end...