[R-390]

[Barry Hauser]

Hi Lee:

There are a number of things that can cause a "some bands syndrome".

You need to list out exactly which bands don't work.  Step through them
looking for known, identifyable signals, like WWV, etc. or whatever makes
sense on that band.  Severe misalignment can cause some signals to turn up
in the wrong places, giving the impression that a band is working.  If it's
a matter of totally dead bands, you can use the calibrator.

You'll should also refer to the manual's explanation of the  vs. triple
conversion, and the bands vs. crystal schemes for the crystal oscillator
deck.  You should also "walk through" the mechanical alignment process.
Chuck's tapes are great, but are not stand-alone references when it comes to
this detail.

Based on what bands are not working (an odd handful, vs. all those over 7
MC's, etc.) you can often "noodle out" the likely culprit.  I've found as
many as 3 bad crystals and each one covers more than one band.  Sometimes
the crystals are good, but the pins and sockets may have some corrosion or
not make a tight fit.  A dose of Deoxit is in order.  A bad or weak tube can
do it.  You could have a combination of a couple of these minor problems
which will render an odd bunch of bands inoperative.

While walking through the alignment, do a close eyeball inspection of the
geartrain and slugracks.  As someone pointed out, it can be caused by a
loose or broken gearclamp.  I've found that a hanging slugrack can cause all
kinds of dead band patterns.  When stepping through the MC bands, the
slugrack tracks the cams on the upstroke, but hangs up partway down on the
downstroke.  It sits there and then re-synchs itself on the upstroke again.
It's hard to spot at first -- work the MC's through the full range -- up and
down.  As the appropriate slugrack(s) are on the downstroke, watch that the
cam followers (little rollers) are actually riding on the cams an not
floating at some point.  If one does hang, unhook the springs and carefully
lift it out.  Dust off the slugs -- no need to use anything on them.  Blow
out or swab out the coils.  Line up the slug springy-thingies -- if they are
all over the place then you can gently bend the springies or use the lateral
adjusters.  While the rack is out of the deck, it's also good time to make
sure the cam follower rollers spin freely.  Drop it back in and check it
without replacing the hold-down tension springs -- it should nearly work
with gravity alone.  If all is well, reinstall the holddown springs.

Spotting a broken or slipping clamp takes a good eye. A similar part-cycle
effect can occur as with a hanging rack.  The resistance on a particular
gear can be low through part of its rotation and it will turn.  Then it gets
to a higher resistance point and slips.  A relatively slight misalignment of
the bandswitch can also cause a mix of dead/live bands.

So, through a combination of "noodling" - logical-deductive analysis with
the manual in hand, and tinkering, as per above,  you should be able to zero
in on the problem.  Most likely it's something simple -- once  you find it.

Barry













----- Original Message ----- 
From: "Lee Bahr" <pulsarxp at earthlink.net>
To: <r-390 at mailman.qth.net>
Sent: Sunday, June 20, 2004 5:47 PM
Subject: Fw: [R-390]


> I went to the Arlington Ham Comm in Texas yesterday and bought my third
> R-390A.  It was a Motorola, serial # 1587.  All meters are intact but the
> chap who sold it to me for $250 said it does not work on all bands and he
> didn't  know what was wrong with it. He said he found it in a
corporation's
> disposable pile.  Now I have 3 of them to restore!  (The other two are EAS
> units).  The Motorola unit looks clean and the front panel is nice but not
> perfect.  All the covers are there.
>
> What would be the most logical reason for some bands not working?  I guess
> crystals would be suspect and maybe switch contacts, if nobody was
screwing
> slugs around in the unit.  (I'll check to see if rack coil slugs are
> moving).
>
> Also, what do you guys think of the latest Electric Radio's article (June,
> 2004) on improving R-390A audio?  I'm thinking of trying this if I
ever/when
> get my radios up and running,
>
> I just ordered the two sets of Hi-Res videos on the R-390A as well as the
> set for the SP-600JX but they have not arrived from Hi-Res as yet.  My two
> cap kits for my first two R390As have been sitting on the work bench for
> weeks now.  Maybe the videos will get me going!
>
> Lee, w0vt
> Houston
>
>
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