[Hallicrafters] S-20R, SX-24 ETC TEMP COMPENSATIG CAP.

[edben]

Guess the old WWII Liberty Ship Radio Operator should speak up again!

About that Temperature compensating capacitor -- Capacitors (condensers)
change their value slightly with temperature.  In most circuits this is of
little significance.  In oscillator circuits, it is critical!.  Most
capacitors "drift" in one direction with temperature change.  The
Temperature compensating ones are of materials deliberately selected to
"drift" in the opposite direction with temperature.  If the drift rate and
the capacitor values are properly chosen, the drift of the circuit
capacitors and the compensating capacitor will directly cancel, resulting in
the oscillator circuit remaining constant with temperature change (warm up
of the circuit).  Stations stay tuned, just like you want them!

Now, about those cold-soldered connections.  They were surprisingly common
"in the old days".  In those grand days that LP records were being
introduced, good radios with 78 RPM changers became obsolete.  My sales job
took me frequently to Fort Wayne, Indiana, home of Magnavox, still known in
those days for "quality" radios.  Fort Wayne had a large top-grade
department store with a resale department for their trade-ins.  I stopped at
every opportunity to look at their Magnavox trade-ins.  I took many home
very inexpensively and installed three speed changers to play the then
current records and one by one, supplied family members and friends with
these fine old radios.

In checking out these "top quality" sets, invariably I found cold solder
joints, straight from the factory!  Not only cold soldered, but
"no-solder-joints, as well!  I don't think I ever saw an old Magnavox that
didn't have at least one bad connection.  They were fine for a few years,
but sooner or later, corrosion set in and those radios ended up full of
noise!  No wonder Magnavox is a "has been" and nothing is left of their once
great reputation.
                                            Ed Benjamin

---- Original Message ----- 
From: <jackiv at juno.com>
To: <hallicrafters at mailman.qth.net>; <hammarlund at mailman.qth.net>
Sent: Sunday, July 06, 2003 1:44 PM
Subject: [Hallicrafters] S-20R, SX-24 ETC TEMP COMPENSATIG CAP.


>
> HI ALL.   CAN ANYONE KNOW WHAT THE oscillator temp compensating cap is?
>
 You would not believe the cold solder joints  which had existed!!
>