OK we have three PCs down and are working our way through it. If you really have a hard problem, here are the steps:
- Buy a test chassis system. This is something that is case-less and let's you swap components easily. It is really useful when something goes wrong.
- Here are the steps, first put in the motherboard and the power supply. Power up the device and make sure the motherboard lights up and the power supply spins. You will need a small button to jumper across the power pins.
- If this works, then put in the processor (you do not need a fan yet) and plug in a monitor and see if you get the POST. This will tell you the processor is alive
In our case, our CPU failed this test. We did find a loose m.2 SSD and it probably shorted out the motherboard.