Mac Plus half screen

I have a really nice Mac Plus with one problem. It only displays half the screen. The rest of the screen is black with a bright horizontal line separating the two halves. I found info online but the information I found is not correct for this issue. I cleaned the boards and reseated all the connections but I get nothing. All capacitors look ok, no leaks or bulging. From what I can tell there are no bad solder points. Any other places to check or information on how to fix?