Rimuru facing decommissioning

Before the holidays, I had the problem that Rimuru would power on in a brain dead state -- fans would spin up, most buses would power their components, and so on. But it wouldn't POST or reach BIOS. Just brain dead. The only way to turn it on or off was the cord and kill switch on the PSU, and trying to hold the power switch on the case would just act like a reset and then total brain death with running fans.

Tried all the good jumping off points: trying to boot off integrated graphics, reseating and walking RAM sticks, etc. Then I took my multimeter to the power supply's ATX main and CPU power pins, and that seemed to be fine.

At that point the only thing I hadn't reseated was the CPU, and I'd have to go to Micro Center for fresh thermal gloop anyway if I did that. So, I decided to drop it off and see what they could figure out. Today, I got my machine back. Reseated memory, POSTS. Well, I hoped their touch was more magical than mine. But no dice.

When I had asked, it was unknown if it fresh thermal paste was used, since the guy doing initial processing had tried reseating the CPU and swapping in another of the same model with no luck. Reseated the processor with fresh thermal gloop, and I've decided that I am taking a new policy on this. If the CPU cooler is connected and it don't catch fire, I'm not effing remounting CPU coolers for this--it's just to much of a pain in the ass in such cramped spaces, and my hands ain't gettin' tinier. If I ever build another desktop, there better not be a huge ass heatsinkage over the processor or I think I'm outsourcing to someone fitting that description.

Anyhow, the machine wouldn't boot and was doing the same thing as when I dropped it off. Gave it a kick and numerous elevated heart rate notifications later while choking on my urge to go Incredible Hulk on the decommissioning, I eventually came back to try a few things.

Tried loading a single RAM channel up and with some fiddly, I got into the OS. To do so, I had to pull the front panel header and rub a nail clipper on the pins. Eventually, I put in the other RAM channel but it didn't seem to make a difference what I did with the memory.

Depending on how I manually short the reset and power switch pins, the system either hangs as before, goes into brain death, or does a sorta reset and may boot or die.

Fiddling around, I noticed that USB ports may or may not have power. I.e., plug in a keyboard while in BIOS, walk it through the ports toggling num lock, cycle back and what the fuck there's no power, and then again and now it works. Stuff like that. In some cases the keyboard would draw power enough to light the num lock LED but wouldn't toggle, and then in some cases it would just be flashing all three LEDs at the top for a while and then go dead.

Anything resembling a "Proper" shutdown like the OS would do leaves the machine brain dead. Have to pull the power and fiddle pins trying to find the right fiddling and timing to boot. Trip the right way and the processor fan cranks and the case fan turns off, and it's total death until power pull.

So at this point, I think a technician who's able to test piece by piece and determine what is failed would be needed. That's beyond my skill without a schematic, and the tiny as hell components to desolder and resolder would make the repair work beyond my ability even if I did have a schematic to work off.

Based on its behavior, I'm inclined to believe the power management chip is screwed up or something has gone awry with the path of power causing it to just "Leak" into systems that should remain unpowered until initialized properly.

To garner a second opinion, I think I may buy one of those PSU tester things to double check my power supply's readings vs my multimeter. Which basically means, motherboard if it's not the power supply. If that's the case, given how much issue it is to get ahold of another motherboard of that model; I may opt to decommission  Rimuru.