"Do Little2" writes:

Zenith Tvs of that era are known for CRT failures, probably a junker.

Look for (4 - 5) 120 Kohm resistors on the CRT board that changed
value... usually well into the Megohms. After changing those resistors
most Zenith's appeared okay again.

Well, there's a lead to try out. I'll let y'all know if anything comes of it.
Thanks!