Hello, I have a self build pc which I've used for several years now. Sometimes upgrading along the way. I've never had any issues with my pc since i built it. Last week i shut the pc down as usual and switched off the psu switch and unplugged the cable like i always have. The next morning I plug everything back in and press the start button on the case and nothing happens at all. So i query around forums and see similar problems so try a few things. I unplugged all the psu cables and took out teh ram in case it was caused by thermal wastage from so much use. Tried it and nothing happens again. So next I went and got a multimeter, tricked the psu into thinking it was connected to a motherboard and started it up, tested the connecters with the multimeter and all show voltage. The capacitors on the motherboard all look good, non look blown. The motherboard pins still have resistance indicating to me that it still works. I then tried disconnecting all the usb cables and power cable and held the power button for 30 seconds to discharge any static build up. That's when my pc came on again, however as soon as i touched the usb port with a cable, off it went again. So now i have a pc that will switch on without having anything but the monitor connected to it. Oh and when i do cause the pc to cut out, it will not start again until i remove everything and hold the power button for 30 seconds and then reconnect and start again.
Finally, on my last attempt a warning came up about missing bios and recovering settings. The pc went through that process for about 1 minute and then started up again as usual. Now im scared to try anything else in case i damage what could already be a damaged pc
Oh and there are no unusual noises coming from anything, the case is a little dusty but its no where near the level of causing a blockage in a fan or any thing like that.
I doubt its an overheating cpu, I cant feel any substantial heat coming from it. And its water cooled so it would be one of the last things i think would cause the sudden cut outs or lack of starting.