[R-390] kilocycle/megacycle movement

Tue, 31 Dec 2002 06:53:54 -0500

Yup.  Some of the cams do go "over the hill"
The 2-4 MHZ cam goes around 360 degrees
The 1 to 2 MHZ cam does NOT make it over the hill.
I think the Y2K manual has a good section telling where
the cams "run to".  Check manual.
And be careful tightening clamps.  They break real easy.

Scott

----- Original Message ----- 
From: "Joe Foley" <[email protected]>
To: <[email protected]>
Sent: Monday, December 30, 2002 7:36 PM
Subject: Re: [R-390] kilocycle/megacycle movement

> Well, some of the cams are supposed to go "over the
> hill".  
> 
> Use a small inspection mirror to see the alignment
> marks. You can re-align them without dropping the
> front panel, too.  Use a hooked dental pick to "grab"
> the hole in the cam, hemostats will clamp the gears to
> keep them from moving if needed.
> 
> You won't be able to see or feel the burrs on the
> split gears until you seperate the two halves and they
> won't be able to move against each other while meshed
> to another gear.
> 
> Joe
> 
> 
> 
> 
> --- Dan Merz <[email protected]> wrote:
> > Hi all/Jim,  I took a look inside and did some
> > reach-in cleaning/inspection but
> > didn't find anything obvious.  And the detent spring
> > seems to be ok though
> > difficult to inspect.  I can't see all the cam
> > alignment marks but noticed the
> > 4-8 mhz cam was off the mark some but was still
> > operating on the right
> > surfaces.  The 2-4 mhz cam mark is not too visible
> > but I noted that it didn't
> > look right as far as how the cores were traveling at
> > the upper end of 3 to 4
> > Mhz -  aha ,  the  Mc/Kc link that started the Mc
> > knob moving occurred when
> > near the upper end of the range around 3.92 Mhz
> > where the core rider was
> > actually dropping on the wrong side of the cam
> > surface.  The cam is out of
> > proper adjustment,  and the cam surface is steep
> > enough on the "forbidden" side
> > that it locks the cam shaft which forces the detent
> > on the Mc  knob to give way
> > to accomodate the motion of the Kc knob as I tune
> > within the band.  Mind you,
> > this doesn't take much force on the Kc knob,  hardly
> > different than regular
> > tuning so there must be some gearing that is helping
> > the detent disengagement -
> > I didn't quite have the patience to analyze that .  
> > Intuitively,  I would have
> > thought it would be the other way around - a lot of
> > force on the cam to hold it
> > solidly enough to disengage the detent.
> > 
> > I haven't figured out where the loose connection is
> > that got the 2-4 cam out of
> > sync,   I guess the gear on the cam shaft since
> > that's closest.  I seem to
> > remember checking these alignments when I first got
> > the radio a couple of years
> > ago and I haven't loosened anything in the gear
> > train except to put the pto
> > oldham coupler  in the right position after I worked
> > on the pto.  I think
> > pulling the front panel is probably the best step to
> > take next so I can see all
> > the cam markings and alignment.  Or is there an
> > easier way?  thanks for all the
> > suggestions,  some of the split gears were checked
> > and seemed ok.  So far I
> > haven't seen a shaft slipping in a gear but that
> > could be happening.
> > 
> > Dan
> > 
> > Jim Miller wrote:
> > 
> > > Sometimes a coil slug will stick at a band edge
> > causing low sensitivity.
> > > Look at the slug rack as you tune at the high end
> > and see if any slugs stop
> > > moving prematurely.  If you see one, tap on it ot
> > wiggle it by hand to see
> > > if sensitivity returns.  If it is a slug that is
> > sticking, you can usually
> > > free it up by loosening the screws that hold it to
> > the slug rack and allow
> > > it to re-seat itself so it doesn't bind.
> > >
> > > Dan Merz 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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> > >
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> > 
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