You can re-use that gear if it's split. Just degrease it and the shaft thoroughly, and epoxy back on. Done many, never had one fail. The teeth still engage just fine despite the irregularity where the split is.

After reflowing the solder in the focus pin at the CRt, I now have nice stable focus. Tint range is pretty awful, and red seems to be too strong even though the screens are set correctly. CRt is pretty tired but very much watchable in a dark room. Still has this very loud buzz in the audio, and I can’t figure it out.

The strong buzz is Zenith's trademark sound identifying the set as a Zenith.

As for the tuner, just adjust the channel 3 tuning slug, since you'll always be using the set on channel 3 and changing the program using an external source (converter box, DVD, VCR, Roku, lo que sea).

I know the buzz your thinking of, and it’s definitely not that. Something is really wrong in the audio section. I didn’t mention, messing with the vertical hold effects the buzz. I already adjusted the FT with the tuning slug. I’ll probably end up using my UHF modulator, if I can’t find a replacement for the plastic gear.

If the modulator is putting out a correct signal, the IF/sound IF alignment is correct, there are no significant circuit issues and the buzz control is set correctly Zeniths are capable of excellent buzz-free audio.

One sei I have where the buzz control doesn't completely kill the issue I've found that on a tube RF modulator I have that has adjustable Audio carrier freq I can adjust that modulator to make good audio on the set (I may adjust its audio alignment in the future).

If the vertical buzz is in the speaker check the filtering, if it is there with the speaker disconnected then the vertical may have issues...Though some vertical systems just like to buzz more than others.

It’s not there when the speaker is disconnected. I’ve ordered replacements for the filters and that should (hopefully) fix it.

For the buzz try the AGC adj & buzz control. Next change the
detector tube. If still buzzes you can adj the detector AKA
quad coil. Dont go more than 1/2 turn & flag your stick so you
can go back where it was. If no joy check around the det.
Never had a component failure so no help there. A few sets went
out with just a light buzz on heavily white scenes. Newer content
& lack of OTA make make this a bit of a compromise.

73 Zeno:smoke:
LFOD !