[R-390] Zero adjust

[Flowertime01 at wmconnect.com]

Dave,

The zero adjust shaft is a threaded bolt through a threaded nut bushing.

Turning the knob screws a bolt through the nut and pushes a clutch assembly.

That assembly works just like an old manual auto transmission clutch, except 
the slip range is just part of a KC knob turn (30 degrees or rotation).

You can see the operation if you turn the receiver up on end and look in 
behind the front panel from the bottom.

You are looking for a big (1 inch dial) flat washer on the end of the zero 
adjust shaft.
This washer pushes three pins in the clutch assembly that allows the 
adjustment to be performed.

That washer is sort of "riveted" to the end of the zero adjust shaft.

The rivet wears off and the washer falls off.

You can get good replacement parts. If you need them ask here and see what 
you get offered in direct mail.

If you are good at it. you can file / machine / grind the shaft back and make 
a new nub to hold a new washer.  

You will likely be better off getting a new zero adjust shaft with washer in 
good shape, only because you do not have a good model to use in fabricating a 
replacement unit.

If that washer is on the end of the shaft and engages the three pins and 
releases the clutch and you still have no zero adjust, then you likely need to 
just clean the clutch.

This is not hard to do. You just may wait until spring. You pull the front 
panel, it hangs down from the wire harness. then you can flush the whole RF gear 
set on the front of the receiver.

You sort of do this out side on the picnic table on a sunny after noon.

You hand a plastic sheet over the hanging front panel to keep the crud being 
cleaned out of the gear train from collecting on the front panel switches / 
meter and parts.


Further work is very doable if required.

Set into it on level at a time to see how far you really need to go t fix the 
problem.


Good Luck with this.

Roger AI4NI

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