Black line on panasonic plasma. Hello I was just recently given a 42 Panasonic plasma model

Question

Hello I was just recently given a 42 Panasonic plasma model number th-42pd60u. I don’t know the history of the set. What the problem is a semi transparent vertical black line just right to the center of the screen. About 9inches wide It only seems to appear when viewing the full screen format, meaning the whole screen is showing a picture; sorry I don’t know the name for that format. I just tried a wide screen DVD and the line didn’t appear, This display was when you get the black boarder top and bottom. I don’t have the remote so I can’t play with the different formats. I’m just hoping to see if you guys had any thoughts on what or where to start fixing? Thanks Jason