Here's a weird one with a 721TS.....
 

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....

Have you tried a different boost capacitor? Watch out. HV, and, high current.
Is height control alright?

There is that 1000 volt vertical capacitor to look out for and the vertical transformer etc

This looks like some kind of "motorboating" of a power supply. Try seeing if the B+ to the vertical is bouncing.

I agree. Also, I've seen some new filters bad.
Vertical output transformer could also be going open.

I replaced the vertical blocking transformer, and the oscillation stopped but I still don't have a full raster. The tuner's been borked with in this thing, and I can't seem to get much of a signal....plus the detent is broken. Too many possible issues with a chassis that's had God knows what done to it, so I'm sending this one on.

Some sets are real dogs. Patience and perseverance is key.:thmbsp:

I hope you will carry on. The thread interest was building.

Not to worry, now I have another which I'll be starting a thread on shortly!

You can learn a lot with comparing two similar sets and two different issues. Hang in there.