[R-390] r390a problems

[Barry Hauser]

While that's a fundamental check -- lineup of the indexing marks -- 
nevertheless it's possible, even if they do, that the situations Dallas
described are still at work.

Slug racks can hang for a portion of their travel.  You have to crank the RF
deck up and down through all the MC positions and pay particular attention
to the racks as they move downwards -- or are supposed to be -- that the cam
follower rollers are truly in contact with the cams.  Tap gently on the
rack(s) to make sure of this as it is often difficult to see.  I had a
similar situation and the symptoms sound very familiar -- dead bands, images
and other strange stuff.  Do the same with the KC knob and watch the cams at
various MC positions.

A loose or broken clamp can also play clever tricks. There may just be a
hairline crack that is barely visible.  The clamp is tight on the screw
side, but loose on the split side and may act like a clutch -- grabbing
through part of the rotation, slipping on the other part, depending on the
mechanical resistance, which varies.  This can be such that at "7+000", the
marks on the cams line up on their respective index points - at least I
think so.  Watch the gears and shafts while working the MC knob -- a gear
may rotate in synch with the shaft for part of the travel, then slip the
rest of the way.  Crank it backwards, slips then grabs, etc.

If a slug rack is in fact hanging up, detach the two rack springs from the
top (they may stay attached at the bottom) and lift straight up.  See if any
slugs are hanging at a substantial angle.  If so, gently bend the "springy
thingy" -- coiled rod -- to straighten.  If when straight, one or more still
doesn't line up well enough with the coil center, make use of the lateral
adjusters.  While you're at it, wipe off the slugs with a clean dry cloth
and use a cotton swab (dry) to clean any dust out of the coils.  Don' t
force anything.  Line up the slugs with the coils and re-install the rack.
It should be able to move up and down without any binding or sticking.
Reattach the rack springs and try again.

You might also have a broken or dropped slug.  Sometimes the "springy
thingy" comes loose from the brass bristol screw.  This can be epoxied.
Slugs can also be glued back together if broken.  Use a very thin coating of
epoxy.  I have variable results with crazy glue on things, but might be OK.
Clean off any excess ASAP.

Very likely based on what you report that it's one of the three.  Just look
very closely at the mechanicals as you turn the knobs -- don't get
distracted, don't assume, and ... don't blink.

Hope this helps & good luck ..

Barry


----- Original Message ----- 
From: "Steve Hobensack" <stevehobensack at hotmail.com>
To: <r-390 at mailman.qth.net>
Sent: Sunday, January 09, 2005 2:09 PM
Subject: Re: [R-390] r390a problems


> I might add to James Miller's email:
> Turn the MC change knob and the KC change knob until the dial reads 7+000.
> Look at the egg shaped cams. Are they reasonably close to the scratch
marks?
>
> Message: 2
> Date: Sat, 8 Jan 2005 22:45:10 -0500
> From: "James Miller" <JMILLER1706 at cfl.rr.com>
> Subject: Re: [R-390] r390a problems
> To: <N4BUQ at aol.com>, <r-390 at mailman.qth.net>
> Message-ID: <000501c4f5fd$9e840640$6600a8c0 at cfl.rr.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Did a gear clamp come loose, causing the tuning chain to get out of sync?
>
>
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