[BrendaAnnD]

The tuning mech on my 640 chassis is driving me batsh*t. The high reduction (fine tuning) part of it only works when it feels like it. In certain parts of the dial, it will just turn without moving the interface between the tuning mech and the semicircular wire interface on the tuner itself. I can move the tuner manually a few degrees and the tuning will start working for a while, till it gets to the next spot where it starts the problem over again. The semicircular wire, which seems to me like it would be the most likely cause, seems to be perfectly formed and good, and it meshes with the tuning gear solidly.

I know this is a planetary system, but it doesn't seem to me that there is enough room inside it for gears. I'm guessing they're doing it with bearings and bearing surface??

Whan can be done to fix this, short of trying to find an entire replacement mechanism? 

Thanks in advance for any and all help.