Hi. I really can't tell from the photo (my monitor is dying), but is that set a table model. If not, did Zenith use the same set up for the front controls on all of their sets from 1968? The reason I ask is that I remember we had a set with a front identical to that one with a 22 inch screen that we got at Christmas, 1968. As I remember correctly, we had major problems with the set after a couple of years with regards to picture quality (sharpness and focus). Some channels were almost unwatchable, and this was with cable. We finally got rid of the set in the mid seventies. Did these sets have a known weak picture tube, or was there some other problem with them as a whole, or did we just get a lemon.

Also, prior to reading this forum (I am interested in old sets, but hae never restored one). I had always thought that the prime symptom of a bad picture tube was diminished brightness.