A few days ago my PC wouldn't start up anymore. No lights, no beeps -- nothing. I quickly borrowed a friend's PSU to see if that was the culprit and it booted up again, so I thought that was it and promptly got a new one (AX860). However, with the new one installed it still didn't do anything.
I read somewhere that a dead CMOS battery could give issues, so I installed a new one and boom, booting... Kind of; it got stuck in a boot loop with no post but at least it's something. I reinstalled the GPU since that was in the way of the battery, but it somehow decided not to boot again. Weird, since I had already tried this before getting a new PSU.
Took the GPU out again, and it booted (still no post from onboard graphics). Placed it back in again to see if that was indeed somehow causing the issue and it failed to boot. However, after taking it out yet again the PC is seemingly dead like it was before. Tried reinserting just about everything except the CPU since I don't have any thermal paste right now to attach the cooler with.
The CPU (8600K) and motherboard (Z390M Gaming) are only a year old, and even though my original Seasonic X-850 had been with me for 8 years, I'm now doubting if it's actually still fine and the problem lies elsewhere. Personally I trust the motherboard the least, but perhaps I've just gotten extremely unlucky with another dead PSU and that's the issue after all.
If anyone has any insights that'd be greatly appreciated, since I've no idea what the hell is going on. I'll try both PSUs in my friend's system when I see him again next week, but I'm not sure I'll be any wiser then.