Yes, if you are not getting the Power On Self Test (POST) than its either your Power Supply or a fried Mobo, and it can be a combination of both.

Its kind of like your battery running dead in your car. First thing you change is the Battery to make sure its not the problem (after making sure its not bad connectors or the ground). Then when the battery dies on you again, you know its either the Alternator or an in-line fuse that isn't allowing your your battery to charge.

Don't make me have'ta Troll ya Bro!