I think it's time to reopen this set and replace the electrolytic capacitors at last. This TV has been extremely reliable since I repaired it almost three years ago. For the last couple of years, it has been played daily. It sits on the desk in my office and I watch the news on it every morning as I check email. Recently, however, the vertical linearity has started to go off.
Linearity controls whether the top half of the picture is the same height as the bottom half.
If linearity is incorrect, one half will appear vertically squished or elongated. In this case, the upper half is starting to look squished, and I'm not able to correct the distortion with the vertical linearity control. Based on my experience with radios, it is probably prudent to replace those electrolytics anyhow, so I will do that as soon as time permits.