New build. Motherboard will not start properly unless 4+4 cpu power is unplugged. Other PSU works fine. Is my PSU faulty?

[callanalex]

Hi friends, hoping I can get some help.

Brand new build, worked just fine for one night, then next morning no luck. Spent ages trying to figure out what was wrong with it. Basically what happens, is I switch the motherboard/pc on, it starts for a second or two, turns off, then on, then off. This repeats over and over. Ended up taking everything out one at a time to try and figure out what the problem was.

I ended up taking everything out of the case and breadboarding with only the cpu+ fan, speaker and PSU. 24 pin and 8 pin power connected from PSU to Mobo.

If I take the 4+4 pin CPU power connector out it the motherboard turns on just fine (obviously cannot boot without CPU power though). I connected my PSU from another build to the motherboard via 24 and 8 cpu power and the motherboard turns on perfectly. Would I be correct in assuming my PSU faulty since the other one works?

PSU is Antec HCG M Series HCG-620M 620W ATX12V / EPS12V
Mobo is MSI h97 gaming 3
using 1 stick of g-skill ddr3 ram for the breadboarding.

 

[callanalex]

help please 🙁

 

[A5TR4L]

You solved the problem yourself, if one psu works fine and one doesn't then it's your psu.