Question Corsair CX750F RGB doesn't work when the CPU cable is connected

[dapda]

Hello, hoping someone can point me in the right direction here. I have a CX 750F RGB modular PSU that I got for my Ryzen 5 3600 CPU and b550f mobo. When I connect everything to the motherboard, the CPU fan turns on for a second and turns off. I also notice that the PSU fan and its RGB doesn't turn on. I played around and removed the CPU cable just to see what would happen and my RAM sticks worked, CPU spun for a good few seconds and my PSU fan was working together with the PSU RGB.

Is this whole PSU faulty or could it just be the CPU E-ATX cable that need replacement? I did try an older PSU that I have and my computer was able to boot up.

 

[--SID--]

You tested with both CPU cables the PSU came with?

 

[dapda]

You tested with both CPU cables the PSU came with?

Yup I did

 

[rene641]

Maybe a stupid question, with the Corsair CX750 PSU you use a cable on one side 8 pin, on the other side 4+4 pin and plug the 4+4 pin into the 8 pin CPU connector of the motherboard?
How did you connect the CPU cable "older PSU" with which the PC booted? What cable and how many pins did it have?