More info. please. Is your set connected directly to local,cable, cable box, etc. Please excuse if you are a tech. I have learned to assume nothing. Also, how old is your set? You may be able to isolate this to a tuner fault by using the audio/video rca jack inputs instead of the coax connection. If you have a vcr, use its' tuner to change the channels. Leave your tv on video 1 or 2 depending upon your connection. If this works, then the tv tuner is faulty. If you have a cable box, many units now have rca jacks to connect in the same way just described above. Best wishes.