オリジナル投稿者： Nathanael ,
The power button is routed through the keyboard ribbon cable. So if the ribbon cable is not COMPLETELY inserted into the slot on the logic board the MacBook will not turn on... I replaced the topcase on a unibody MacBook recently and it wouldnt power on. I have seen several instances of this being the only problem with a MacBook after a repair... The ribbon cable is hard to insert all the way so be careful! Hope this helps!