Question Probably not power supply but what else could it be?

[AverageCheapskate79]

So I'm working on my custom build it's a tomahawk b550 motherboard, with a 4500 CPU and a 5700 XT GPU and the tower is what is causing the problem it's in Roseville D100 atx case, I bought it for my son for the RGB capabilities but he was too young to enjoy it so I confiscated it and made him a different PC, but this is my first decent gaming computer when I made it 2 years ago, I have not had a problem like this come up before I installed new fans that didn't have the lights on them because the fans that came with the case required you to use a hub that also came with the case and I didn't like the hub it didn't work half the time so I ordered new fans I put them in everything worked, just fine. Then yesterday out of the blue when I turned the computer off in Windows by pressing power off, it didn't power off, it restarted. So I tried it again and same result. So I just did a hard power off by holding the power button and then today I turned it on and used it and when I went to turn it off again remember that the problem is still there so I was looking in the chassis and I did see a wire coming from the reset LED switch on the case, but it wasn't plugged into anything and I looked in the manual for the main board and didn't see anything that required it so I'm thinking it was for the hub that I'm not using anymore, but on the main board in the very bottom very right corner there's a two pin plug that looked like something it would work but I didn't even see it mentioned in board manual
Regardless I plugged it in and then did a hard power off and unplugged it and moved it to the living room so I had better light to watch it and see what's going on and when I plugged it in in there with the same power cord the PC would not turn on, so what I've done so far is tried to unplug the LED switch from the main board same result, I try to different power cord same result, different outlets same result no lights turn on so I'm thinking it's got to be the PSU. Troubleshooting where do I go from here I've never done this one.

 

[AverageCheapskate79]

Yeah I forgot to mention the PSU it's a Corsair 650 gold it was used and on the back of it it says RM 650x. It came in a box for the same PSU only for an 850 so I'm assuming the guy I bought it from needed a more powerful one. But I've had no problems with it since I bought it about a year and a half ago so this would be the first problem with it if that's the case.

 

[AverageCheapskate79]

I figured it out checking the wires the two that go to the power switch one of them is loose and was disconnected I reconnected it connected the power cord to the PC again and press the power button and magical change-o it works.