I have a R15 receiver I get 0% signal strength on the A and B sats but can get 95 % on C. I have tried the dish in a couple locations the mast is plumb I have worked on aligning for a long time and I can only recieve signal on C. I am getting the same thing using 2 different 50 foot cables. The setup has worked for years then one day boom the problem started. What could it be?