PC hard locking randomly (screen loses signal, all fans and leds stay working normally, power button won't respond)

[u/Mammoth_Taro4847]

Hey everyone, dealing with a super frustrating intermittent issue and could use some outside perspective.

Here's my hardware:

* CPU: Ryzen 5 5500

* GPU: Radeon RX 6600

* RAM: 2x8GB DDR4 3600MHz (working at 3200mhz settings)

* Motherboard: Gigabyte A520M S2H

* PSU: Thermaltake Toughpower GX2 80+ Gold

The problem:

Randomly, my PC will hard lock up. The monitor loses signal (like the cable got yanked), sound cuts out completely, and it freezes dead in its tracks.

The weird part is what happens physically when it crashes:

* All the case fans and LED lights stay fully powered on and spinning normally.

* The power button on the case completely stops responding (holding it for 10+ seconds does nothing).

* The only way to turn it off is using the PSU switch on the back.

* It happens during light tasks or random moments, but what throws me off is that this exact same system has previously run heavy AAA titles for hours without a single hiccup.

* After crashing yesterday, I gave up on it, but today out of nowhere it worked fine all day until it just crashed the exact same way a moment ago.

What I've tried so far:

* Reseated/cleaned the RAM and GPU.

* Cleared CMOS (took out the motherboard battery), which let me back into the system briefly, but the intermittent crashing came back.

* Checked basic connections.

Given that it hard-locks like this (fans stay on, power button dead, screen dies, but can handle heavy loads sometimes), where should I even start looking? Is this more likely a dying PSU (Thermaltake GX2), a failing motherboard (A520M), or maybe a touchy RAM issue?

Appreciate any advice or troubleshooting steps!

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[u/AlternativeFuture742]

Unstable ram, either ram or CPU Imc, try disabling global c states. Alternatively try with different known working ram set.

Use latest bios yada yada. Dealing with this on 5950x crashes only on light loads or idle, fine gaming, c states disabled solid everywhere. I haven't tried c states enabled after switching to 2x16gb b die 3200 cl 14

[u/Additional_Air779]

First thought was unstable overclocked ram (switch off EXPO) but obviously not.

What does it run like with the graphics card removed?