[Collins] 75S-1, more adventures.

[Glen Zook]

There is an adjustment on the PTO for making sure that
the apparent frequency doesn't shift when changing
sidebands.  Actually, the PTO does shift frequencies. 
But, when properly aligned the tone doesn't shift when
you shift frequencies.

See the manual for this procedure.  Only takes a few
seconds to accomplish.

However, if the receiver has had the 500 Hz mechanical
filter and the optional BFO crystal installed, then it
will shift frequencies when you go to CW.  In fact,
since the receiver actually receives in the CW
position, some type of optional CW filter has to have
been installed!  The receiver came from the factory
with the CW filter not installed.

You could take delivery of the receiver and then
return it to the factory for the CW filter to be
installed, you could have it installed at a service
depot, or you could purchase the "kit" and do it
yourself.  However, for some reason, Art Collins would
not let a 75S-1 or 75S-2 receiver be shipped from the
factory with a CW filter installed (this changed for
the 75S-3 and 75S-3A of which every receiver shipped
from the factory with a 200 Hz CW filter installed).

The only known 75S-1 that was shipped with the CW
filter installed when it was built now sits in my
shack here in Richardson, Texas!  It cost the original
owner his job with Collins Radio!  It seems that the
fellow (an employee in the Dallas plant) got the
receiver through the employee purchase plan (employees
paid less than wholesale for Collins equipment) and
made a "deal" with someone at the Cedar Rapids plant
to get the CW filter and the optional BFO crystal
installed at the time of manufacture (early 1958).  

Art found out and called the guy on the "carpet".  the
employee decided that it would be better to "resign"
than suffer the "wrath" of Art Collins.  Then, the
fellow traded off the receiver to another local
amateur who used the receiver for a few weeks and then
stored it in his garage for over 40 years!  A "local"
to me got the receiver in a trade deal with the second
amateur and then immediately traded the receiver to
me.  It was only after I discovered the factory
installed (you can tell by the glyptol marks on the
connections, the actual soldering, etc., that this was
installed when the receiver was built) filter that I
started checking and found out the story!

The plastic tubular capacitors are the same paper type
capacitors that are often called "black beauties". 
They can range from brown (in the 75A2 and 75A3) to
black (75A4) to other colors in other radios. 
However, paper type capacitors start going bad before
they are soldered into the circuit!

Glen, K9STH


--- kiyoinc at attglobal.net wrote:

I didn't see anything that I would call a "black
beauty" although there were some old plastic Sprague
caps under the deck.

The 75S-1 shifts frequency when I flip from SSB to CW.
 I don't like having to retune the signal.

=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco

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