Question PSU failure? (Or hopefully not something for menacing)

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Jun 29, 2018
Three days ago I built a brand new build.
Before continuing, the core components are as follows:

Mobo: MSI x570 MPG Carbon Pro WiFi
CPU: AMD Ryzen 7 3700x
RAM: 32GB Corsair Vengeance RGB Pro
PSU: Corsair RMx 850 (I know 850w is a lot for my build, but it was on sale at Best Buy and was in the A tier of the PSU hierarchy)

Everything was going fine until this morning when I was moments from joining a match in Destiny 2 and my PC suddenly shut off completely. No warning, no blue screen, and no immediate clues.

I tried pressing the power button. Nothing. I went over the the back and flipped the PSU switch off and on, then pressed the power button. Case fans (and only case fans) swung a few millimeters before halting and then failing to do anything else.

The power button then needs to be turned on and off before it will try (and fail) to boot again the same way as the first time after the crash. I’ve done no troubleshooting at this point because I had to go to work. I’m hoping I just got a faulty PSU and I don’t have to deal with something more sinister like replacing a faulty CPU or Mobo. Does anyone have any ideas?


Even with the power switch off, the psu still gets some power. Unplug the psu from the wall before trying again.

Is there a reset button on your psu?

Possibly one of the psu cables has been dislodged.
Check for that on both ends of all of the cables.


Sep 5, 2019
No beeps?

Since I do not know your level of troubleshooting ability, I will just go step-by-step.
We'll focus on the PSU, given that even new PSUs can fail out-of-the-box. I believe that your PSU, like most of them nowadays, came with a ''PSU tester'' or ''jump starter''? (Small, black, rectangular 24-pin receptacle that fits over the 24-pin motherboard end of the PSU cable).

1.) Remove and inspect the AC cord. Does it plug solidly into the wall and into the PSU?

2.) Make sure the PSU is OFF at the back, then remove, inspect and re-seat ALL modular cables. By ''inspect'', I mean check for burning, arcing, melting of the connections, ESPECIALLY ON THE PCI-E WIRES FOR THE GPU!! I have found that sometimes, PSUs can have intermittent connections (which can cause no end of operational issues), and with the advent of ''fully modular'' PSUs, any connection problems have now DOUBLED!

3.) If this fails, then you will have to remove the PSU and all the modular cables from the system for a ''bench test''.

4.) Install 24-pin and 8-pin CPU modular cables into PSU.

5.) Plug the PSU directly into a WALL SOCKET. Turn off ECO MODE (or corsair equivalent), and install the ''jump starter'' on the 24-pin cable.

6.) If you have no ''jump starter'', AND you feel comfortable doing it, you will have to power up the PSU manually, with a wire or short pin. (Look it up on-line, as their pictures and videos are much better at explaining what has to be done than I could describe here.)

7.) If the PSU fan ''spins up'' and stays running, it's at least alive. If not RMA TIME!

8.) If you hove a REAL PSU TESTER with LEDs and/or LCD display, you could use that.

9.) Again, on-line, and if you manually jump-started it, and you have a DMM/voltmeter, you could check all the pins for their respective voltages. there are 7, independent voltages and signals on 24-pins, (PWR_ON, PG, 5VSB, 3.3V, 5V, 12V -12V and all the respective grounds), so get busy!

10.) In the mean time, do you have another, known functioning PSU? If so, install that one into the system to see if the system powers on. (If it is also ''modular'' use only the modular cables that it came with! No mixing-and-matching!)

11.) Or, if you bought the Corsair RMx 850 PSU from a local brick-and-mortar store, you could just box it up and take it to them to troubleshoot...

12.) With the ''replacement'' PSU, or if you are confident that the Corsair is working, install only the BARE MINIMUM In your case, the 24-pin and 8+4-cpu cables to the motherboard, and the PCI-E cables to the GPU. Make sure you are using ONE(1) PCI-E MODULAR CABLE for the 8-pin and ONE(1) PCI-E MODULAR CABLE for the 6-pin connection(s) (DO NOT use a dual-end PCI-E cable for both!) Power it up and see if it posts.

If this doesn't solve the problem, you probably have more than a ''PSU issue'' to address!!
Try the above first, and the Forum will address any further issues, should they exist.
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Jun 29, 2018
Thanks for the advice so far, guys. I’ll test it further when I get home after work.

If it boots “normally” afterward would that mean my other components are fine and that I just need to exchange the PSU? Luckily I bought it at Best Buy and am in return policy, so it’ll be an easy return.
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