{Collins} Dial Slippage on Collins 51S-1

Tuning dial slippage in a 51S-1 is usually the result of too much lubricant.
Since the tuning assembly is all gear driven, there had to be some sort of
clutch function, otherwise, you'd wring off the PTO shaft when you spun to
an end stop.  That clutch mechanism is by way of a wave washer held to the
tuning knob's shaft.  If you squirt oil on it it WILL slip.  I would suggest
dropping the front panel (It really is easy one you look at the mechanics of
it.)  then remove the knob shaft assembly by taking out the two 4-40
phillips screws an either side of it.  On the back side of the knob shaft,
you'll see the gear that engages the anti-backlash ring gears.  That's where
the wave washer is.  Clean it out with some degreaser (or lacquer thinner)
and re-assemble it.  Once you clean out any lubricant, you should have
sufficient torque to overcome the gear losses.   Be sure to pre-load the
anti backlash ring gears, otherwise the tuning will be noticeably sloppy.

One more item that's a fault of too much lubrication is lock-up of the
little black plastic number rings that show through the window.  If anyone
has used a petroleum based lubricant on them, they probably have swelled
slightly limiting their movement.  The only fix for that particular
situation is to dis-assemble it all and drill them out to the proper

Hope this helps, Charlie k3ICH

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