Hi MMD & Frank,  You are doing a great job in troubleshooting, but
there is nothing wrong with the motor -- the problem is the plastic
gear in the gear box.  If you go to this page of the Mechanical Music
Digest Archives you will find the information on how to remove the
gear box and where to get a new gear:

  http://www.mmdigest.com/Archives/Digests/200805/2008.05.14.04.html 

If you feel you can do the job yourself, you can simply order a new
gear from Ferdinand Pointer or simply send him the whole gearmotor
unit and he will tear it apart and install a new gear for you.

One very important part is that make sure you take good measurements 
of the roll shaft as you take the parts out, as it is very hard to get
the alignment for roll tracking just right and you will spend hours or
days adjusting it.  I know -- I have done three of these players for
customers and it is not easy.

Musically,
Larry Norman, from the beautiful Blue Ridge Parkway in Virginia.
Last week we traveled to the COAA rally in Chattanooga, Tennessee,
and we took the parkway back from Cherokee, North Carolina, and the
parkway avalanche has been cleared and the parkway is fully open, and
the flowers, the trees, and the scenery is just breathtaking.  Enjoy!