Making some more progress on the set. I went though every resistor in the horizontal circuit and replaced quite a few that were way out of spec, or completely open. I fired the set up after each replacement to make sure nothing went wrong, and to enjoy seeing the picture get better and better with each step. I still have (at least) two problems with the video currently. One problem I could not get completely sorted out with resistor replacement in the horizontal circuit was a bit of tearing at the top of the screen.
It was easiest to photograph the phenomenon by injecting video right at the grid of the video amp and adjusting contrast until it showed up. It is possible to get a stable picture most of the time, but when there is full motion video on screen it will occasionally tear horizontally at the top of the screen, just like the picture above but some times much worse. The last set I worked on had a Sams for it and gave a procedure for horizontal adjustment. I cannot seem to find one in the Rider for this set however. Maybe it's just a matter of adjustment that I'm missing?
My other problem is before the video amp. I'm getting some trailing ghosting in the picture.
I haven't dived into this problem just as I would like to get the horizontal sorted first but thought I'd share.