[R-390] R-390a Tuning Problem

[Larry Haney]

Hi, Yes, sometimes oil will find its way onto a shaft where it's clamped,
but the clamps can't grip the shaft tight enough to stop slippage with oil
on it.  And if you overtighten the clamp, it may crack.  The only solution
is to  clean the shaft and clamp spline.  The problem point is probably
where you correct the alignment problem.  If you correct it at the Oldham
coupler, that's probably where it's slipping.  To test it, you can grab
onto the vfo shaft and turn the KC knob a little to see if you can see some
slippage there.

Regards, Larry

On Fri, Jul 5, 2024 at 12:03 AM <fwbray at mminternet.com> wrote:

> I purchased an R-390a a couple decades ago and replaced the suspect
> capacitors, etc.  I haven't used it a lot in the interim due to high
> urban noise but it has a tuning issue that I never resolved.
>
> Specifically, there appears to be mechanical slippage somewhere in the
> Kilocycle tuning mechanism.  I have made sure that all the cams are in
> the correct position at 7+000 and that the PTO is also correctly
> positioned.  I have also checked to see that there is no excessive play
> in the Oldham coupler.  Everything appears to be tight.
>
> If I turn the Kilocycle knob rapidly, it appears that the PTO gets out
> of synchronization.  I haven't been able to identify any broken or loose
> clamps in the gear train.  I can readjust things so that are again
> aligned but the problem repeats itself.  The gear train is clean and
> lightly lubricated.
>
> Has anyone encountered and resolved this issue.
>
> Thanks.
>
> F.W. Bray
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