What you describe would happen if you have a bad separator, or a bad 6" long piece of coax from the separator to Tuner 1. As long as you have current firmware and so a signal strength for both tuner 1 & 2, you don't need to do anything. If you don't show signal now when you select tuner 1, you still have a problem. TV1 doesn't necessarily use Tuner 1. If you change it in that screen, you essentially swap which Tuner is used. It may stay swapped until you use the Swap button in Single mode or stength screen in Single/Dual. If you can hit PIP and get pictures through both Tuners, you probably don't have to do anything.