Computer Shuts Down Randomly While Playing

Hey.
Iv'e recently upgraded my gpu from an rx 580 to a Vega 64.
Since the upgrade my computer will completely shut down anywhere from 5-30 mins of playing.
This did not happen with the 580.

At first i thought it was the gpu shutting down under load. But after trying all my other games on high setting, Beamng was the only one that had the issue.
Iv'e stress tested successfully, Everything passed on Burnintest.
Iv'e tried undervolting the gpu/cpu with no luck, although while undervolting, the crash would take longer to occur. So i thought maybe the PSU didn't have enough juice. But the PSU fan is supposed to start at 60% load, which it never did. Also i would have thought 750w (62 12v) would be fine.
Using a PSU calculator, a 550 PSU was apparently the minimum.
Tried old and new drivers with no luck.

MOBO -Steel Legend B450
CPU - Ryzen 3500x
GPU - Vega 64 srtix oc
RAM - 16g Balistx 3200
PSU - aerocool p7 750w Platinum
WIN 10

My temps before shutdown were fine, sub 75-gpu, sub 60-cpu


Help would be appreciated. I really wanna play
Thanks.

Edit: Just stress tested psu with OCCT and my pc crashed within a minute. So probably the PSU?!?!

 

Wouldn't be the first time an Aerocool PSU gave up, ex-Aerocool PSU user here.

 

Sounds a lot like the PSU, had a similar issue not too long time ago and there was nothing to see in the event viewer. Turns out the PSU was dying, so I would get that replaced. It's not a good idea to run with a bad PSU.

 

Is it possible that the gpu could be the culprit for an abrupt shutdown?
I ask because i purchased the replacement used from Ebay, it was very cheap for a vega. The seller did have 100% feedback.
--- Post updated ---

The psu is only a few months old. Could be a faulty one?

 

Doesn't matter if it's a few months old or few years old or brand new. Computer hardware rarely breaks from wear and tear.

 

look like a PSU problem try to buy a new PSU

 

My brother is getting a new 550w psu and a new gpu within the next week. How would you suggest i troubleshoot to find the culprit?
550 may be a touch weak.

 

i'd reccomend going to a 750watt to be sure

 

Get a GOOD 650-750W power supply.

 

Iv'e just purchased a 1200w (to be sure)

 

Out of interest what PSU did you buy?

 

Kolink PSU Continuum 1200W 80 Plus Platinum Modular Power Supply