Intermittent PC black screening and not powering on

[saad2019]

Specs and troubleshooting steps are listed below. 

 

I'm having a weird new problem with my PC. The computer was built a few years back and has been running without issue. About a week ago, I left my computer on for a few minutes while I went to the kitchen, and when I came back, the display was black and wouldn't get a signal from the computer. I tried restarting it, however, it still didn't display anything. After unplugging the PSU and restarting, the computer started working again. This time, the screen was flickering as if the graphics card was failing, with lines appearing and disappearing horizontally across the monitor. I'll list out the symptoms here:

 

1. The computer will power on, but the screen flickers like described above. After a few minutes, the computer will suddenly restart with no warning.
2. The computer will not power on. Instead, it will display show the VGA light on the diagnosis LED's, which will disappear after about a minute. At this point, the peripherals light up and the fans start spinning faster 
3. The motherboard will not display any diagnostic lights, but all the components will spin up, but the screen stays black. 

 

Here are the diagnostic steps I have taken:

1. Completely disassemble and reassemble the computer (no impact)
2. Purchase a new power supply (did not resolve the issue so I returned the PSU
3. Purchase a new motherboard (did not resolve the issue but I have retained the old motherboard for now)
4. Reset the BIOS on both motherboards, which sometimes makes the computer boot up but then it will crash again. 
5. Disconnect the power supply from all the components and then reconnect it, which usually resolves the VGA light issue but then the PC crashes again shortly after. 
6. Try powering on with no peripherals connected other than the monitor (no impact)

Here's where it gets a little bit interesting. I tried starting up the computer outside of the case, and it ran flawlessly for an hour or so without any hiccups. When I put it back in the case, it started crashing again, so I thought that maybe something was causing a short and making the PC crash. I took it out again and left it running outside of the case for 2 days. I then cleaned the case and removed any other debris inside the case. I put the computer back in, and it was still crashing. However, now, it is not powering up again outside the case either, which means it's probably not the case that's causing the issue. 

 

I'm completely stumped at this point and don't have any ideas so I was hoping you guys might have some suggestions on what to try. 

 

The specs of the computer are: 

• AMD Ryzen 7 3700X
• MSI B450 Mortar Max (when the issue started), currently running MSI B550M PRO VDH WIFI
• ASRock Radeon RX6800 16GB
• 16GB Corsair Vengeance Pro RGB 
• Corsair RM750 PSU (have tried a Corsair RM750e as well)
• Samsung 980PRO M.2 NVMe
• Fractal Meshify 2

[Blasty Blosty]

Is it the front panel connectors? Have you tried it in the case without plugging them in? It's the only thing I can think of. Or perhaps a case fan?

[saad2019]

1 hour ago, Blasty Blosty said:

Is it the front panel connectors? Have you tried it in the case without plugging them in? It's the only thing I can think of. Or perhaps a case fan?

I've tried both with the front panel connected as well as without. I also thought it mightve been the fans or maybe the fan hub but the issue still happens without the fans so I'm guessing it's not them. 

[Blasty Blosty]

Either the case broke your computer or it was really weird timing when it worked

[saad2019]

47 minutes ago, Blasty Blosty said:

Either the case broke your computer or it was really weird timing when it worked

Do you know which component it would've taken out? Both the motherboard and GPU are under warranty so if something's dead, I'm hoping it's one of those two. 

[Blasty Blosty]

1 hour ago, saad2019 said:

Do you know which component it would've taken out? Both the motherboard and GPU are under warranty so if something's dead, I'm hoping it's one of those two. 

Only way to find out is to test with known working parts if you have any spares