welcome aboard !
For your Zenith 19" may I recommend a 4 tube hybrid.
Millions were built & they are very easy to deal with. A
better one will have a chromacolor CRT & give a great pix.
They were made from abt 1972-1976 ( B-F line sets).
They were made in 19,23 & 25" sets. Solid state sets
from Zenith of the same era are also great to restore.
Came in 17, 19, 23 & 25". The 17" is my favorite.
Easy to find parts & its rare to find one with a bad CRT.
The design of all these sets are similar & easy to learn
how they work.
CUL
Zeno