The power board is the large red board in the Nomad.  The transformer that we wanted to replace is the large black box on the right side of the board.  To replace the transformer we needed to remove the board.  To get the board out, we unplugged everything from the board.  While we were unplugging cords, we labeled them to know where they belong.  We then removed the front control panel of the Nomad.  The control panel was removed so that we could remove the floppy drive so that there was enough room to slide the power board out of the robot.  Once the floppy was removed, we unscrewed the power board from the Nomad and slid it out.