This 1989 KV-20TS20 Trinitron has a horizontal line flickering problem on all sources. They appear to be random. This is a still image for example. It's subtle but it's there. I'd like to fix it.
https://youtu.be/9x77Ha8or4A?t=8s
What is the source of the issue? Capacitors in the power circuit? Tapping the set for cold joints doesn't do anything.