Are you measuring with the board in the TC or just on the bench? I would expect the fan to spin with power on even if the board still failed to boot. Measure the power circuit on the board so you can see if it is shorted.. and not allowing the supply to start up.
One of the best tools around is an appliance wattmeter.. which you plug into the wall and plug the appliance into it to see how much power it uses.. they show a lot of details.. and if the supply draws next to nothing it is being shorted and not turning on.
Main boards for these will be a substantial portion of the cost so you won't find them as a part.