Hmm... My usual first step is to try another RF cable. Next is the power cord, as sometimes the wires can break inside but it still works and feels warm. Looking at the male end of the power pack cord, you'll see a black line on the metal tip. That seperates + from -, so use your multimeter set to 50v and touch both of those metal pieces the black line is between. You should get 9-ish. If not, that's the trouble. If it's more complicated than that, the power switch itself would be my next guess.