So a couple weeks ago I bought a b-stock EVGA 850w B5 psu, problem was it didn't include the 18 10 to 24 pin motherboard connector, which just arrived today.

So yeah finally excited to put everything together and when I try to power on my system...nothing happens except a quick flash from a mobo led and the 1080ti lights and an attempted spin of the cpu fan.

So I get my old psu and hook everything up and the computer posts and everything is working fine.

The new psu does pass the self power test, is there a definitive way to make sure the PSU is actually dead? Could it be that the cable that was sent was defective?

Fwiw system build is: Asrock b550m pro4 5600x 1080ti 16 gb ram Evga 850w B5