[SeaSonicPSU] Computer powers down without warning

[EagleEye]

Computer built in 2013, current hardware:
3570k - CPU @ 3.8 Ghz
7970 - GPU
2x4GB some RAM I forget, - DDR3
P8Z77-V-PRO mainboard
Samsung 840 SSD 120GB
Seasonic 650 W fully modular PSU - [url]http://www.newegg.com/Product/Product.aspx?Item=N82E16817151088[/url]
CPU and GPU is watercooled, CPU temps spike at 60C under load, GPU around 50C under load.

Started playing new games bought on the Steam sale, when suddenly the computer acts like I just pulled the plug and turns off. A few seconds later the computer turns back on, acts like nothing happened. No windows error messages, nothing.
Start up the game again, same thing happens several times in a row. Try previously stable games like FO4, same thing happens, now it won't stay booted into windows for more than a few seconds.
Loaded up memtest86, ran one pass fine, I left, came back a few hours later to see the win10 lockscreen, so I have no idea if it passed the other memtests. Tried to run memtest again, now it turns off in the memtest menu.
Pulled the CMOS battery, reset Mainboard to factory settings, still no dice. The PSU does feel pretty warm when compared to the rest of the computer, not hot to the touch, but warm, I can see the fan spinning as well.
Last night I tried to play games again, computer was stable for about an hour before shutting down constantly again. Finally said fuck it and threw an old 500 watt PSU in, no problems so far.

Went to the windows event viewer, lots of event 41 Kernal-Power - The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.
15 events in 2 days.

At this point I'm about ready to RMA the PSU, is there any testing I can do on the PSU to confirm it's failing? When in the BIOS all the voltages read normal. Could it be overheating? I'm going to run memtest again for 20 passes and see where that gets me, although I wouldn't expect failing RAM to power off completely like someone just pulled the plug.

[lavacano]

You changed the PSU and all your problems went away, I think it's safe to say your PSU is the problem :v:

Go ahead and run that memtest anyway just because it never hurts to test silly shit, but other than that I'd say go for the RMA

[EagleEye]

[QUOTE=lavacano;50616454]You changed the PSU and all your problems went away, I think it's safe to say your PSU is the problem :v:

Go ahead and run that memtest anyway just because it never hurts to test silly shit, but other than that I'd say go for the RMA[/QUOTE]

Its just really strange, it did the exact same thing a year ago with FO:NV, I pulled the plug overnight and it worked fine up until a few days ago, on the 27th. Like how do you even prove that the PSU is just randomly turning off?
I just sent an email to Seasonic about my symptoms, I don't expect them to be helpful but I really need this RMA to go smoothly.