[R-390] unstable BFO note on R-390A
Joe Foley
redmenaced at yahoo.com
Sat Dec 16 21:25:54 EST 2006
--- Bob Young <youngbob53 at msn.com> wrote:
> Thanks for the tips I'll definitely check them out,
> what exactly is the
> oldham coupler anyway?
+++++++++++
If you turn the radio upside down and remove the
bottom cover you will see the PTO. If you follow the
operating shaft toward the front panel you will see a
coupling that allows some deflection of that shaft,
that is the Oldham coupling. It has three parts, four
if you count the spring, which is sometimes missing.
The spring is to keep backlash out of the coupling
sections, it SHOULD be hooked to the two pins that
stick out of the outer sections of the coupler. There
should also be some gap between the three sections,
about 1/32" should be enough.
NOTICE: If that gap is not there it could cause just
the problem you have, jumpy tuning, because it is
putting pressure against the insides of the PTO. I
just remembered that from one of Nolan's posts from
the past. Also, check the mounting of the PTO,....
just because.
Joe
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