[HowardWoodard]

I think my thinking is upside down but just flipping it raises another question. I think the gap that I was adjusting when turning the bottom screw is a red herring. I think that bottom screw is meant to be tight, securing the trimmer cap to one side of the variable cap. The top "cap nut" is probably the adjustment device. While that makes sense and agrees with the schematic, it raises the issue of how the mica is held in place. Right now, if I loosen the cap nut, the insulator and the mica become loose, allowing the mica to slide around and, in fact, allowing the copper to come into contact with ground.

Obviously, I can put a little adhesive under it, but I doubt that's what the factory would have done. Should there be a little dielectric grease on the back side of the mica to help hold it in place? Or something else?

Just about done...