TV sound

I have analog TV, first I had problem only with one channel, there was some extra noise heard together with normal sound, but I thought it was some problem with receiving signal, and then some other channels started to make noise including DVD channel and satellite so my friend who was trying to do something but couldnt do said there is something wrong with the "chip" and i need new one, so what do you think how much does that kind of "chip" cost?? Or do you think there is some other problem?