Question My fiancee's computer is going black and restarting. Any ideas?

May 1, 2020
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Backstory: Her computer is made out of my old rig. FX-9590, Asus Sabertooth 990FX, R9 390X, 16GB DDR3, and a Rosewill 1000W Power Supply. The power supply is so massive because I had the 9590 and an AMD 7990 back in the day.

So her computer started to micro stutter every second and run insanely slow, so we decided it was time to upgrade her rig. I swapped out the CPU, Mobo, and RAM for a Ryzen 3 3200G, Asrock x370 Killer sli/ac, and 2x4GB DDR4 T Force Delta. I didn't do anything about drivers really, except upgrade BIOS and install the drivers for the new parts, same windows installation. The micro stuttering every second is still happening occasionally but that is not why I am here.

Problem: While she was playing games, her computer would go to a black screen, then eventually restart. It would happen one or two hours into gaming, so I thought it was overheating, til I checked temps, and nothing is hot at all. It's now starting to restart even a few minutes into just booting into windows.

What I've tried: I added 3 more fans to see if it really was overheating, but none of the temps are high at all. I've started to think that it is because the power supply is now about 6-7 years old. I downloaded OCCT stress test tool, and 21 seconds in, it froze the computer. I tried doing just the PSU test in that program. CPU and GPU both ran at 100%, it didn't freeze, and didn't crash, so I'm confused. I ran Windows' memory diagnostic tool and both passes were fine.

Any ideas?
 
May 1, 2020
4
0
10
Do you have another PSU to test with?

What model is this Rosewill PSU? How old is it? Rosewill is essentially Newegg's house brand and many of their units are not very high quality.

It is a Rosewill Hive 1000S 80+ Bronze.

I have a PSU in my personal rig I could throw in and see if it stops.