[SOLVED] Random restarts with PSU in one system, but not the other

[theonlynewts]

I built a new system a couple weeks ago and have had random restarts when active and idle.
Everything is stock speeds and all drivers and BIOS are updated.

PSUs:
-Corsair CXM 750 W 80+ Bronze Certified Semi-modular ATX Power Supply
-EVGA 500 W 80+ Certified ATX Power Supply

New Build:
-Intel Core i7-9700K 3.6 GHz 8-Core Processor
-MSI MPG Z390M GAMING EDGE AC Micro ATX LGA1151 Motherboard
-G.Skill Ripjaws V Series 16 GB (2 x 8 GB) DDR4-3200 Memory
-Samsung 970 Evo 500 GB M.2-2280 NVME Solid State Drive
-Samsung 860 Evo 1 TB 2.5" Solid State Drive
-EVGA GeForce RTX 2070 8 GB XC ULTRA GAMING Video Card

Old Build:
-Intel Core i7-4790K 4 GHz Quad-Core Processor
-ASRock H97M PRO4 Micro ATX LGA1150 Motherboard
-G.Skill Ripjaws X Series 4 GB (2 x 2 GB) DDR3-1600 Memory
-Samsung 850 EVO-Series 500 GB 2.5" Solid State Drive
-Crucial MX200 500 GB 2.5" Solid State Drive
-Seagate Barracuda 3 TB 3.5" 7200RPM Internal Hard Drive
-EVGA GeForce GTX 1070 8 GB SC Gaming ACX 3.0 Video Card



I've run just about every stability test I can find and have had no issues with temps or crashing during these.
I've watched just about every number in HWMonitor and everything from voltages variance to temps seem to be fine based on my googlings.
I've turned off the auto restart feature of Windows, but still don't get a BSOD. Just restarts.

When I run the new build with the EVGA 500W, everything is fine. No crashes for several days. But as soon as I put the Corsair 750W in, I walked away and within an hour I had my first unexpected restart.
However, when I run the Corsair 750W in my "old" build, it seems to be fine there.
I'm worried to leave the 500W in my new build because most of the PSU calculators I've tried estimate I need between 450-550W and I'd prefer to have a little breathing room.

I did try swapping the graphics cards for a couple hours and it seemed like I got a lot more frequent restarts with the 750W/GTX1070 combo, but I didn't leave that pairing long. The RTX2070 seemed fine in the old build for that time.

Is my Corsair CXM 750 W 80+ Bronze likely bad or is there some compatibilty issue I'm missing? Maybe this has nothing to do with my PSU at all?

 

[theonlynewts]

I'll probably jinx it, but I put in a Seasonic FOCUS Plus 650 Gold PSU today and haven't had any issues since.