My custom built desktop has had problems off and on the last 6 months. Most commonly, when turning the machine on, it powers everything up but never gets to POST.
I've replaced or borrowed all my hardware trying to figure out the bad piece: 3 motherboards, 2 PSUs, 2 graphics cards, 3 CPUs, 2 hard drives, 2 optical drives, 2 CPU fans, countless RAM sticks, even set the machine up outside of the case and still get the same result.
Sometimes the machine powers up and works great. This usually occurs after replacing a piece of hardware. Fan, drive, PSU, etc. But eventually it goes back to the blank start.
With this latest iteration of components, I believe I've narrowed the problem down to the motherboard. When powering the machine on (with minimal components: graphics card, RAM, CPU & CPU fan) the machine spins up for a few seconds then shuts itself down. Then it turns itself back on again and off again and so on and so on until I hit the PSU switch.
When I unplug the small power cable used to power the CPU, the machine turns on and stays on, but never POSTs. I've tried two other CPUs with the CPU power cable test and get the same results. I know my CPUs are good because they came from working systems.
So this leads me to the motherboard. The problem is, I've replaced the motherboard before, only to have the same problems happen again down the line.
I'm thinking about selling everything and starting fresh.