[John Folsom]

John, I am afraid I am a poor student. I had forgotten your Sylvania was one of those very interesting RF HV supply sets, and would use s separate transformer (choke?) to drive the horizontal coils. I also note on the schematic the yoke coils are wired in parallel, so my supposition about the balancing capacitor is probably not valid. But hopefully when you reverse the leads on the yoke, your ringing issues will get better.

Good thing you don't have troubles with the RF HV coil, as some of these don't have a replacement.