Question Multiple power supplies not powering pc

Jan 11, 2020
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I recently changed out significant hardware on my PC. I basically moved my SDDs and HDDs to a new case with a gigabyte-b450-aorus-elite-atx-AM4-motherboard and a Ryzen 2700x. Also installed gskill-aegis-32-gb-2-x-16-gb-ddr4 ram.

The problem started when I tried to use my corsair 650w psu, it wouldn’t register any power when pressing the button. Oddly enough a corsair 550w psu I own works just fine. I’ve had a few issues since the upgrade, but occasionally the monitors just go black while everything else appears to be running fine. Reading around, I decided to go get a new PSU, corsair 750w. The power button now triggers all fans/leds including the cpu, but immediately powers back down.

I’ve double and triple checked the connections, I can plug in the 550 and it’s fine. Struggling to find a cause now I’m completely baffled.