[Hallicrafters] SX-28 gearboxes

[Mike Everette]

I'm in the process of restoring an SX-28 (non A), and
after removing the gearbox and cleaning it, was going
to replace the bandspread dial drive cord.  Referring
to Doug Moore's excellent article, I started looking
for the cord... lo and behold, my gearbox has no dial
cords other than those which activate the band-in-use
pointers.

There is no pulley behind the big gear in the
bandspread mechanism; or anywhere else, except for the
aforementioned pointer-cord mechanism.

My gearbox is completely, 100% gear driven.  It looks
like a clock in there.

And, yes, everything turns just fine -- dials,
capacitors, knobs.  The action is extremely smooth.

The bandspread mechanism appears to have the same feel
at the end-of-travel as the main tuning, in that there
is no sharp stop; but the bandspread shaft is not
concentric like the main.  I assume there is a form of
clutch action on the bandspread shaft but have not yet
figured out how it works.

This gearbox appears to be original to the radio.  The
metal "sandwich" looks, on the outside at least, to be
quite similar to the photos in Doug Moore's article.

This SX-28 is a rack mount version.  I have no idea if
it is ex-military.  I do know that it spent part of
its life in an industrial plant.

Is this type of gearbox somehow unique?  (Truth be
told, I think I got lucky....)  I have asked several
people, including Chuck Dachis and Doug Moore, but
nobody seems to have ever encountered one like this.

I may take some digital photos of it if anyone's
interested.  If there might be any other clues that
would identify a production run, please let me know. 
(Yes, I know that information is very sparse.)  To
answer an anticipated question, my receiver's serial
number is gone.  Someone punched a 1-inch diameter
hole in the rear chassis apron, and the plate, right
where the number should be.  I can see only enough to
know that it is "H-" rather than "HA-."  And it is
definitely an SX-28.

73

Mike
WA4DLF


		
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