I built my own desktop about 3 years ago. It has worked pretty much flawlessly since then.
However, the other day I went to turn it on and nothing happened (and I do mean nothing). Not a single light came on on the outside of the case or on the motherboard. No fans spun up, and no outputs worked.
I tried looking online, and most outlets pointed at the PSU as the most likely source of the problem. I removed my PSU and did the test where you jump the power on switch, and it worked. The fan came on, and using my digital multimeter I check that all of the pins were outputting power.
I also read that the CMOS battery can sometimes go bad in a computer this old, so I replaced it. Still unresponsive.
As far as I can tell, all of these signs point to something being very, very wrong. Because of all of the COVID crap going on, buying half a computer's worth of parts just to diagnose the problem doesn't make financial sense right now. I also cannot exchange extra parts with my friend nearby for the same reason, and I also don't want to damage any of his parts.
Are there any other ways I can test my machine before I write off the motherboard and CPU as a total loss? I have nothing but time these days, so if it is a matter of trying something, I might as well.
And yes, everything was plugged in, no fuses were blown, and the power supply switch was on. I left the computer exactly as I normally would when I shut it down for the last time. I didn't move it around or do anything that would unseat something like the RAM.
Just some more context:
The only thing that was strange was that the night before, I plugged in a flash drive into one of the front USB slots on the case (there are two of them) and both slots suddenly stopped working; my headphones were being used in the other one. I plugged the same flash drive and headphones into another computer and they worked fine. Perhaps that has something to do with it, but I'm not sure. I continued to use my computer for about an hour after that, and turned it off and on a few times to try and fix the problem, before finally shutting it down for the night.
Also, there was not major/obvious catastrophic failure, such as blue smoke or a burning smell. Every thing looked fine visually as well.
Not sure these are entirely relevant, but here are the specs:
-CPU: Intel 6600K (NOT overclocked)
-MB: MSI B250... mortar? I think
-GFX: Sapphire Radeon RX 480
-PSU: Corsair CX 550M
-RAM: 2x8GB Kingston Fury