I can't remember ever seeing this type of oscillation in the vertical before.
This set was restored by someone and had a broken width coil when it came to my bench, along with potential tuner issues that still have to be checked and confirmed. The height control is at max, and when reduced it collapses to a vertical line that is steady and doesn't jump.
Here's a video:
https://www.youtube.com/watch?v=GcKl...ature=youtu.be
Recapped, and all large power resistors check within spec. Need some ideas on this one....