Since the unit had been electrically overloaded there is no telling what extent of damage occurred. I would suspect the main board and power supply to be the most likely components. You will need to do a thorough investigation of the unit to see what else has been damaged. There is a good chance that there will be visible signs of burnt components. You may also try to disconnect various components and see if the startup sequence changes at all as this may give indication of what areas contain the problem.