Psu+mobo+cpu/hsf.

Nothing else plugged in or connected.....just the power switch.

Power it on.
If the cpu fan does not spin your down to 3 parts or the power switch.

Move the mobo out of the case on to a piece of card board remove power switch.

Locate the 2 pins the power switch connected to and short them for a second.

If it does not power up your down to 3 parts.....pick one.