To check the power output of the amp, just insert the end of a jumbo paperclip in the set one F connector and touch the positive lead of you DMM to the paperclip and the negative lead to the threaded portion. If you have power there start looking for the ends of the cables. I have two pieces, one from the power supply to the antenna and it is in the area between the ceiling and roof, one that connects to the antenna.
Sometimes that one in the ceiling is a bear to get to.