[R-390] kilocycle/megacycle movement

[Barry Hauser]

Hi Dan & Gang:

In addition to a worn, bent or loose detent spring/plate, check carefully
for a loose or broken gear clamp.  A broken clamp, or one that isn't
positioned right, may snug up with the bristol wrench, giving the false
impression that it's tight.

The situation sounds familiar.  I got one unit in here a few months ago and
noticed the MC knob creeping.  One broken and one loose clamp.  I don't
recall which ones.  You have to look carefully behind the panel as you
rotate the KC knob with the MC set in various positions, including the 4 MC
position.  The mechanics of the gearworks is such that the backlash varies
over its travel, largely due to the spring tension on the slug racks..

As suggested, gunked up gears could do this, but they'd have to be pretty
bad.  Check all clamps using the close eyeball inspection method.  And,
whatever you do, don't blink!

Barry





Dan wrote:
> Hi,  I haven't used my  390a much over the last 2 or 3 months and I was
> listening on 80 meters tonight and found a problem tuning up near 4
> Mhz.  It seemed dead there and I could tune in stations down near 3.9
> somewhat better (I started listening on another set for comparison to be
> sure the band wasn't dead).  After awhile I noticed that the megacycle
> knob seemed to move off its "lock" position and was moving as I tuned
> the kilocycle knob.  It did this sometimes and would get off the band
> position but not always.  Is this most likely a lubrication problem?  I
> really never was able to pick up a known signal at around 3.99 Mhz and
> I  tried rocking the megacycle knob to improve things,  or to find if
> something else was "hanging up".  I haven't lubed the set since about 2
> years ago when I did a pretty thorough job in this regard and everything
> seemed very free.  I'll pull it open tomorrow and take a look but was
> curious if there was an obvious known component that causes this kind of
> symptom. It seemed ok on other bands but I didn't spend a lot of time
> checking.   thanks,  Dan.
>
>
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