Why wasn't this Zenith roundie repairable?

[Michelle]

Growing up, we had a Zenith color TV (a "roundie", according to a Google search).

One day, I remember the set developed a problem where the black edges of the screen started to pulsate, and they encroached on the picture a bit.

The effect looks a bit like slow-motion waves.

Apart from the wavy black edges, the picture itself was OK.

Anyway, the TV repairman soon came, gave my dad some bad news, and we got a new color TV.

My question is what exactly was the set suffering from? I'm just curious if it was a terminal problem, or if the set was repairable.

Thanks!