Question Motherboard not responding only when CPU is installed

Aug 2, 2022
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I moved my once functional computer into a new apartment, and now it won't boot.

Specs:
  • MOBO: MSI MAG B550 Tomahawk
  • CPU: Ryzen 5600x
  • HSF: Stock Cooler
  • GPU: Nvidia RTX 2080 Super
  • PSU: Corsair TX650M
  • RAM: 4x G.SKILL 16GB ZX8 D4 3600 RIPJAWS
I followed this troubleshooting checklist: https://forums.tomshardware.com/threads/no-post-system-wont-boot-and-no-video-output-troubleshooting-checklist.1285536/

Some of the steps I tried: I reseated every component and replugged every wire. PSU passed the paper clip test and powered the HSF fan, case fans, and GPU fans along with case LEDs and motherboard LEDs if the CPU was removed (the red "Missing CPU" debug light is on). I was able to successfully flash the bios without CPU to the latest version (released 06/06/22). I removed the CMOS battery for 5 minutes and replaced it. I power cycled between each step.

In fact, everything responds as expected until I plug in the CPU. As soon as I installed the CPU and secured the HSF, I get no response when I hit the power switch. Remove the CPU, and the motherboard gives me the red CPU debug light while the fans and lights run without a hitch. I tried breadboarding with the CPU, HSF, PSU, and one stick of RAM (in the correct slot) and got the same result. Repasting the CPU didn't change anything. CPU is not visibly defective; pins are all intact. MOBO also does not have any visibly broken components.

Oh, the computer did POST once while the CPU was plugged in. I had just redone the thermal paste for the second time. Initially, the CPU debug light was on, then turned off, and the system POSTed. I was able to access the bios screen, but when I pressed continue setup, the screen stayed black while the fans kept running. After turning the computer off, I was never able to POST again, even after subsequent applications of thermal paste. For what it's worth, I used the Corsair XTM50 thermal paste, and I put a pea-sized blob on the CPU before squishing the HSF on top.

Is the CPU the likely culprit, or am I missing something?

Unfortunately, I do not have another system on which to test individual components.
 
I moved my once functional computer into a new apartment, and now it won't boot.

Specs:
  • MOBO: MSI MAG B550 Tomahawk
  • CPU: Ryzen 5600x
  • HSF: Stock Cooler
  • GPU: Nvidia RTX 2080 Super
  • PSU: Corsair TX650M
  • RAM: 4x G.SKILL 16GB ZX8 D4 3600 RIPJAWS
I followed this troubleshooting checklist: https://forums.tomshardware.com/threads/no-post-system-wont-boot-and-no-video-output-troubleshooting-checklist.1285536/

Some of the steps I tried: I reseated every component and replugged every wire. PSU passed the paper clip test and powered the HSF fan, case fans, and GPU fans along with case LEDs and motherboard LEDs if the CPU was removed (the red "Missing CPU" debug light is on). I was able to successfully flash the bios without CPU to the latest version (released 06/06/22). I removed the CMOS battery for 5 minutes and replaced it. I power cycled between each step.

In fact, everything responds as expected until I plug in the CPU. As soon as I installed the CPU and secured the HSF, I get no response when I hit the power switch. Remove the CPU, and the motherboard gives me the red CPU debug light while the fans and lights run without a hitch. I tried breadboarding with the CPU, HSF, PSU, and one stick of RAM (in the correct slot) and got the same result. Repasting the CPU didn't change anything. CPU is not visibly defective; pins are all intact. MOBO also does not have any visibly broken components.

Oh, the computer did POST once while the CPU was plugged in. I had just redone the thermal paste for the second time. Initially, the CPU debug light was on, then turned off, and the system POSTed. I was able to access the bios screen, but when I pressed continue setup, the screen stayed black while the fans kept running. After turning the computer off, I was never able to POST again, even after subsequent applications of thermal paste. For what it's worth, I used the Corsair XTM50 thermal paste, and I put a pea-sized blob on the CPU before squishing the HSF on top.

Is the CPU the likely culprit, or am I missing something?

Unfortunately, I do not have another system on which to test individual components.
Try a different wall socket.
Try a different power cord.
Take the pc to a friends place and test.
 
Aug 2, 2022
2
0
10
0
Try a different wall socket.
Try a different power cord.
Take the pc to a friends place and test.
Would a different wall socket or power cord change what I'm seeing? I already confirmed that the PSU can handle multiple computer fans and lights.

That being said, I did test a different power cord that I know works (it's currently powering my monitor). I have also tested multiple power outlets around the apartment.

I just moved into a new city, and I don't really know anyone yet. Maybe I can talk up some people at a nearby computer store? :sweatsmile:
 

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