Today I got a really good picture out of the Zenith. I found that the AGC was turned up just a tad too much, and after re-adjusting it, things shaped up on the screen very nicely.
Now, a new problem has developed.
Tonight, I was making convergence adjustments, and lost focus and could hear something sizzling.

Oh great now what? Anyway, it turns out that the focus tube had a small light show goin on inside it towards the bottom of the tube. I swapped it out twice, but on each replacement, I still have the small light show and sizzling.
Any ideas? What could cause this condition?
Naturally this would have to turn up just when I thought I was nearly finished!