I've owned for approx 3 yrs. Today I was watching a show on my Panasonic TH-50PZ80U and all the sudden the sound went away. From the lowest volume setting to the highest, no noise at all...Please help!

Hello!
First move: unplug your broadcast provider's box, wait for a minute, then plug it back into power source. I mean: leave all the connections intact, just unplug from power source. It might be just power cord or power adapter. If that's not the case, please do the same with TV. Unplug it from wall outlet, wait a minute, plug it back in. It's a next step, if your "box" won't take care of the problem. If that won't take care of the issue, refer to owner's manual for "reset" procedure. Worst case scenario: you might need to replace main board inside or your TV.
good luck,
Thanks,
Alex.