[R-390] Removing Megacycle Change shaft

[Jacques Fortin]

Hi Paul,
That circular "ring" is a part of the travel stop mechanism and is actually
pinned to the shaft.
Reference to your sent picture, if you turn the MC shaft 180 deg. did you
see a hole on the other side ?
If yes, you have to use a 3/32" drift pin thru that hole to push the lock
pin out.
Be careful, as you will have to re-install it (and all the travel stop
disks) when you will re-assemble it.
And this is not the only difficulty: there is also a circlip locking the
shaft on the other side, plus a lot of shims.

IMHO, you will have to remove the whole RF deck from the set to be able to
work properly on that problem.
Another way is a disassembly + reassembly of the front plate.

Last idea: if you can remove the remnants of the broken clamp, you can
machine a 2-part clamp that use 2 screws to jam the gear to the shaft.
Advantage: no lock pin to remove (will be a PITA, guess how I know) and no
front mechanism plate removal and reassembly.

Some other people on this forum can have different opinions, if so, go on !

See the attached pictures (from my "spare" R-390A RF deck).

73, Jacques, VE2JFE in Montreal

-----Message d'origine-----
De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la
part de PAUL ROCHE via R-390 Envoyé : 15 juin 2026 20:24 À :
r-390 at mailman.qth.net Objet : [R-390] Removing Megacycle Change shaft

Just got my first R-390A and the Megacycle Change shaft just spins and
spins; the Oldham coupling clamp is broken. But the problem is to remove the
shaft I need to remove the circular "ring" attached to it. I am looking for
a setscrew, but this doesn't look like any setscrew I have ever seen! I
might have to drill it out unless someone has a better idea; what is this
thing and how to i get this circular ring loose so I can pull the shaft to
add a new clamp?
 
Paul
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