Question Troubleshooting help please

Apr 24, 2021
Hello, new guy here. Here's what I'm working with. It's a custome built pc. Initially what happened is she was working great. Just died one day. The psu was still from the initial build in 2011 so I figured it finaly gave up the ghost so I replaced it. It ran for a few hours then same thing. I bought another psu, thinking maybe I got a bad one or something. It fired up but ran less then 5 minutes. So I thought the power where I was living was bad as the lights where doing weird things all the time. So I bought a pile of parts and moved. Currently it has

a corsair icue 465x rgb case (brand new),
a mis x370 motherboard,
an amd razer processor (I don't remember which)
A pny geforce gtx 1080 graphics card
32gb of g.skill ram 16 gb of which I just installed (after this started).
A new samsung 970 Evo plus m.2 drive
and two 500gb raptor hard drives from the original build
Thermaltake toughpower gf1 750W.
All plugged into a APX RS 700 battery back up system.

This too fired up, was working great great for all of 3 minutes then died. No power, won't fire up any more?
I imagine if I put another psu in it will work another 3 minutes before it dies. What could be causing this? Bad mother board, graphics card? Crappy opperator?