Best I figure, my Seasonic X-850 is dying a slow death..

All that said, I figured I'd run it by the more experienced ones and all the troubleshooting steps I've done...

1st- Power Supply is a 2016 Seasonic X-850 KM3. Its seen near 24/7 on-time since I got it. Its been powering rig in specs since 2017. Off and on F@H. I've always kept it meticulously clean. I've pulled the cover off at least 6 times since I've gotten it and used a soft bristled paint brush and canned air to keep dust off of it..

2nd- So here are the symptoms- While playing ANY game, it will flat out randomly powerdown. Its as if the 12V rail just dies as the 5V and 3.3V rails stay live as my board uses the 5V rail to power RAM. This is where it gets weird though- Idle, does fine. Haven't had any issues. It will run F@H 24/7 on both CPU and GPU (same time) just fine. Even drawing 340W through the GPU, for 5+ hours during testing I did this weekend. It even handles Furmark "BURN TEST" just fine. Memtest passed 5 runs. Its just the moment you hit a game, it will eventually do it. No warning. No artifacts or errors. Then it gets even weirder- When it happens, I have to flip the switch, wait 2-3s then flip the switch back on. Upon powering on, it refuses to boot until it fails to boot for the 3rd time when it resets BIOS and then it'll boot just fine and tell me BIOS was reset, check settings. I load up my profile and restart and it boots up just fine on the first try.

I did try dropping to 2 sticks of RAM also. Same results.

I have tried dropping the power limit on the GPU while gaming to -15% and it helped for a few days..

I pulled the PSU out, checked it over, no burnt components etc.. all perfectly clean.

My best guess is- Caps are drying out and GPU, while gaming is throwing too much of a transient load spike and the caps can't supply the go go juice so the PSU kicks off. What do you all think?

Its an old PSU and has served me well, so I have no issue getting a new one. Looking at a Seasonic PRIME-TX 850 or Vertex 850. Leaning towards the PRIME as I don't see any need for the ATX 3.0 standard and I would get better use out of the higher efficiency of the TX-850.


Posted this on TPU too. lol
I had a corsair 850 flake out at 8 years and corsair 750 go out at 7 years... this 10 year business for 24hr a day pcs I dont think works. I now look at PS age when pcs act up...

BTW when you swap it out make sure to remove all the old PS cabling and only use the cabling that came with the new PS. Learned that lesson the hard way (melting cabling and fire). Kind of the hard way I learned how 650w PS's werent up to snuff with the new GPU's at the time... blew 2 of those puppies and seeing that happen can make you shit a brick.
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Probably the PSU. Sounds like some of the stuff happening to you happened to me. I've had random shutdowns, i've had sleep modes that wont wakeup. I've had the press the power on/off switch before it did anything. I've had a time where i just left it overnight and the next day it fired right up.
The final straw was when i was idling my PC one time and i left it running. at some point it shut down and no matter what i did it wouldnt wake up anymore. PSU switch, PC restart, CMOS battery reinstall/new battery, leave it for awhile and come back later. Nothing.
Installed a new PSU and up it started. Like you i was using an ancient PSU which was probaby several years passed its best before date.
Well, just got the system powered back up. Gonna get a new CMOS battery tomorrow maybe though as it didn't want to POST until I reset the BIOS. So idk.. if this doesn't fix it.. guess that gives me a reason to upgrade.. although.. that will mean some hefty spending. lol
I don't think the CMOS battery is your problem. If it were drained the BIOS would already have been cleared, so you wouldn't have needed to reset it.
Well, it did fix the issue of the no-POST. So must have been. My guess- just a weak battery. Its voltage was under 2.6V.