Question PC won’t power on when CPU power cable plugged in.

[severian2012]

After installing a new PSU. The PC would not power on. After some troubleshooting I found that it will no longer power on if the cpu 8pin connector is pluggged in. It’s not the new PSU as the old one, which previously worked fine, does the same thing now. I am wondering if I did something when swapping out the PSU that fried by motherboard or CPU. The only thing I can think of is that I didn’t have both ends of the 24 pin connector connected to the PSU when I first tried to power it on, only the longer one . It is modular and I was unfamilar with it and didn’t realize both ends needed to be plugged in.

My questions is would this cause the motherboard or the CPU break? I have no way of knowing which one is the culprit. Any thoughts on what could have happened and which component I should try to replace is appreciated. I’m thinking it’s the motherboard but I’m not sure.

 

[CountMike]

After installing a new PSU. The PC would not power on. After some troubleshooting I found that it will no longer power on if the cpu 8pin connector is pluggged in. It’s not the new PSU as the old one, which previously worked fine, does the same thing now. I am wondering if I did something when swapping out the PSU that fried by motherboard or CPU. The only thing I can think of is that I didn’t have both ends of the 24 pin connector connected to the PSU when I first tried to power it on, only the longer one . It is modular and I was unfamilar with it and didn’t realize both ends needed to be plugged in.

My questions is would this cause the motherboard or the CPU break? I have no way of knowing which one is the culprit. Any thoughts on what could have happened and which component I should try to replace is appreciated. I’m thinking it’s the motherboard but I’m not sure.

Did you by any chance use same cables that came with old PSU ? 8pin cables are different from PCIe a AT power on MB.

 

[severian2012]

Did you by any chance use same cables that came with old PSU ? 8pin cables are different from PCIe a AT power on MB.

No, I used the new cables. I did use the old power cable that goes into the wall.

 

[severian2012]

Following up on this. I replaced the motherboard and it solved the issue. However, now my GPU won't power on. I swapped it out with an old one to test it and that one worked fine. So, I think I bricked my GPU as well.

Question:
To anyone's knowledge could doing what I did fry both the motherboard and the GPU? Luckily the CPU is fine.

To clarify, I believe the error I made was only connecting one of the ATX 20pin cables to the PSU. The motherboard end was fine, but the other end of the cable had two connectors, and I only connected the larger one. It was my first modular PSU so I wasn't sure how they should connect. Obviously, it didn't power up and I tried to turn it on multiple times. The PSU fan would spin for a second then stop with a clicking noise.

I believe this was my error that caused this, but I would like to make sure in the small chance that it is a faulty PSU and it will continue to bust any new parts I put into it.

Thanks for any help.

 

[Misgar]

I believe the error I made was only connecting one of the ATX 20pin cables to the PSU.

I've quite happily plugged old PSUs with just a 20-way connector into 24-way motherboards with no problems. Not ideal, but on old low power boards, I've got away with it. The extra 4-way connector just provides additional 12V power, in parallel with the 12V wires in the main 20-way connector.

More likely if it was a modular PSU, you might have plugged an ATX12V (CPU) cable into a PCIe (GPU) outlet on the PSU, but they should "key" the connectors or wire them up so this doesn't happen. Just a guess.