[Amps] corded dial drive help

[Scott Townley]

My project amp (specifically BTI LK-2000) has one of those ganged-corded 
dial drive mechanisms to turn the input and output band switches 
together.  Is there any reference mat'l that someone can point me to on how 
to maintain/adjust these types of things?  One is slipping and doesn't 
respond to my attempts at figuring out how it works (I can't see at all how 
it works, actually).
TIA,