I work on these old radios because I enjoy doing so. There are members here who have a lot more experience than I do. For me, the easiest part is the electronics. I find the mechanical aspects can be a real challenge.
The double gears that interface with the worm drive have always been a source of intrigue for me. Well now I have come across a Delco instruction on how to adjust them. When they are not adjusted correctly you end up with that annoying play in the dial drive.
Basically the gear to the left, looking from the front of the tuner is not attached to the shaft. It is connected to a spiral spring. To adjust it, move the worm drive away from the gears by removing one of the mounting screws, rotate the left gear against the spring to the limit, back off four teeth and them re-engage the worm drive.
I hope this information helps.
