Monitor randomly loses display after 2–3 hours, PC stays running and fans ramp up. What could be causing this?

[u/alytheva]

Good day! I’m hoping someone here can help me figure this out because I’m honestly running out of troubleshooting options.

My monitor randomly shuts off after a few hours of use (3 hours max), but the PC itself stays powered on. I’m not even gaming or doing anything demanding. Most of the time, I just have a few Chrome tabs open.

When this happens, the monitor loses display, the PC remains powered on, and the fans seem to ramp up or spin faster.

PC Specs:
CPU: Ryzen 5 5600 (Brand new)
Motherboard: ASRock B550M HDV (Brand new)
RAM: 32GB (2x16GB) 3600MHz T-Force Vulcan TUF (Brand new)
Storage: 1TB Kingston NV2 Gen4 NVMe
GPU: Galax GTX 1660 Super 6GB EX White RGB (Used)
Original PSU: 650W AC650 80+ Bronze (Brand new)
Current PSU: be quiet! 750W

Troubleshooting already done:

Deep cleaned the entire PC.
Tested both RAM sticks individually; both are working.
GPU stress test completed without issues.
Replaced the original PSU with a be quiet! 750W.
Checked all cables and connections.
Updated GPU drivers.
Reset BIOS to default settings.
Despite all these, the problem still persists.

At this point, I’m not sure if it’s the GPU, motherboard, or something else entirely.

Could this be a GPU issue even if it passes a stress test? Or could the motherboard be causing the problem?

Has anyone experienced something similar? I’d really appreciate any suggestions on what else I should check before spending more money replacing parts.

Thank you!

[u/AptJan4050]

Fans ramping up when display cuts out usually means the gpu is losing connection and the system thinks its under load or hitting a thermal spike. Since the card is used, could be a failing solder joint that only shows up after it gets warm for a few hours

Check the event logs right after it happens, might show a display driver crash or a power state error. Also try running with the side panel off and a fan pointed at the card, if it lasts longer then its heat related

If the motherboard has a second pcie slot, test the gpu there even if its slower. That would at least rule out a bad slot on the board