Hey all,

So I recently bought a new PC from Cyberpower PC. The computer runs completely fine during mundane tasks, and I can even plays games as long as I'm on low-mid graphical settings. However if I try to push the computer with higher settings (or run a stress test like FurMark), the computer will eventually shut off. When it does this the power button is unresponsive, and I have to flip off the PSU's power switch and flip it back to be able to boot up again.

I've monitored my temperatures during various reproductions of these shut-offs, and the CPU only gets into the 50s to low-60s C, and the GPU never goes above ~73 C. Neither should be causing a shut-off, so I suspect that the PSU is unable to handle a heavy load on it (Apevia 800W, I've heard bad things about these). Overclocking was by default enabled on the CPU as well, but I also disabled that and am still getting the shut-offs during heavy load.

Because of that I bought a EVGA SuperNOVA 850 G3 (80 Plus Gold) PSU so I could test with a quality PSU. The PSU came with a testing pin (it clips onto the 24-pin as a ready-made 'paperclip test' of sorts), I tested the PSU by itself and it spun up the fan and purred. Glad that it seemed to be working, I installed the PSU into my system, made sure all of the cables were snugly snapped into place, but unfortunately I can't get it to boot. When I flip on the PSU switch, I see orange lights come on on the motherboard, but when I press the ON button, all of the fans momentarily spin up, but the computer doesn't boot. It seems like I'm getting power to the motherboard, but I'm not sure why it won't boot.

To make sure no components were damaged during the swap, I put back in the Apevia PSU from the original Cyberpower build, and the computer boots again. As far as I can tell the new EVGA PSU should be compatible with my motherboard, but for some reason I can't get it to boot up.

Here are my specs from the PC I purchased from Cyberpower:

CPU: Intel i7-9700K 3.60GHZ 12MB Intel Smart Cache LGA1151 
Motherboard: ASUS Prime Z390-P ATX w/ WiFi 802.11AC RGB, USB 3.1, 2 PCIe x16, 4 PCIe x1, 4 SATA3, 2 M.2 SATA/PCIe 
GPU: GeForce(R) RTX 2070 SUPER 8GB GDDR6 (Turing) 
PSU: Apevia 800W - Standard 80 Plus Gold Certified Power Supply
Memory: ADATA XPG Z1 16GB (8GBx2) DDR4/3000MHz Dual Channel Memory
CPU fan: MasterLiquid Lite 120mm ARGB CPU Liquid Cooler with Dual Chamber Pump & Copper Cold Plate

Any help would be greatly appreciated, thanks for taking the time to read!

Thanks for the reply, Sajin, yes I'm using only the EVGA cables for all of the connections: the 24-pin to the motherboard, the 2x 4-pins for the cpu (connected to the motherboard), the 6 and 8-pin for the gpu, and the various SATA connections to my harddrives. I couldn't even use the Apevia ones if I wanted, they were built into the internals of that psu.

There was a Molex connector that was hooked up to two RGB 3-pin cables from my Liquid cooler that I wasn't able to figure out how to connect to the EVGA psu. The Apevia psu had a molex adapter that plugged into them, but I've made sure not to hook that up with my EVGA psu and just leave them unplugged. I tested that the computer booted with the Apevia psu and those two RGB connectors unplugged, and it still booted, so I assume I should be able to do the same with my EVGA.

Keep in mind when you use the tester it's best to have nothing else connected to the PSU. Also it shouldn't be an issue but did you replace the cable from the wall to the PSU with the new one? I try the new one and see if that does anything and if it doesn't you could always try the old one to rule out that cable if the PSU tester doesn't get it to spin the fan on the unit.

Sounds like you just got a bad psu. I'd rma it.

Thanks, LeeM, yup just did another check of everything (including a fresh attempt at re-installing), and it's configured like you say: CPU 8-pin is plugged into the PSU, and the 4+4pin end of it is plugged into the motherboard (I even attempted using the second CPU cable included with the PSU, no luck with that cable either). The 24-pin cable is plugged into the motherboard and the opposite 18+10pins are both snugly plugged into the PSU.
 
Maybe a stupid question, but do these ends of the motherboard cable look correct? Are they supposed to be missing a metal pin on each side?

(in case those imgur embeds don't work, here are the respective images:  & )
 
Thanks again to everyone offering their help!
 
EDIT: Looks like I can't embed images or links? I'm guessing because I'm a new forum member. Replace the (dot) with . and try this: imgur(dot)com/a/zsIrhDr  &  imgur(dot)com/2IwHLwM

Yes, that is normal.