In response to your request in 010314 MMDigest on how to proceed with
restoration of an Aeolian-Hammond Player Organ, I would submit the
following.  I have owned two of these curious instruments over the past
34 years, so I'm somewhat familiar with their construction and their
foibles.

>From a restoration standpoint, the two main elements to consider in the
Aeolian-Hammond Player Organ are the pneumatic player system and the
Hammond organ mechanism proper.  A complete restoration addresses both
systems.

The Hammond organ proper consists of its 91-tonewheel generator, the
chorus tone generator, the drawbar assembly and the match transformer,
the pre-amplifier, and, external to the player organ proper, one has
the original tone-cabinet(s) with its own vacuum tube amplifier and two
electro-dynamic speakers.  Since the Hammond organ itself can be played
independently of the pneumatic player system, one can test the various
parts of the electronic organ sequentially and identify any problem
areas.

Schematic diagrams are still available for the Hammond Model BC organ,
which is what the Model BA Aeolian-Hammond Player Organ really is,
without its player system.  Obtaining parts for the Model BC Hammond
organ can be quite difficult; however, these are fairly hardy machines.
Assuming the prior owner did not drench the tonewheel assemblies with
tone-generator lubricating oil, one may be fortunate enough to find
that the Hammond organ itself is mostly intact.

In my experience, the Hammond organ pre-amplifier was the source of
a great deal of trouble due to prior "rebuilding" by a careless
repairman.  Also, the original BC Hammond organ drawbar assembly is a
nuisance because each drawbar has 7 dead spots within its draw-length.
Unlike later drawbar assemblies which had continuous action, the BC
organ drawbar assembly has these dead spots and they cannot be
eliminated.

Parenthetically, the Hammond BC organ with its D-20 or DR-20 tone
cabinet has very limited tonal resources, especially compared with
even inexpensive modern key-board synthesizers.  These limited tonal
resources can be vastly improved by substituting a good Leslie
rotating-horn organ speaker for the original Hammond D-20 tone
cabinet.  One can use an original Leslie 31H "Highboy" or the Leslie
22, 22R, 122, 122R or 122 RV speakers.  All of these Leslie organ
speakers have pre-amplifier inputs designed for the oldest Hammond
organ "balanced" line outputs, which is what one finds in the Model BA
Player Organ's pre-amplifier.

The main components of the pneumatic player system include the rotary
vacuum pump with reservoir, three pneumatic assemblies respectively for
the two organ manuals and for the 12-note bass-pedal switch assembly.
Each pneumatic assembly consists of a primary assembly with its
associated pneumatics which operate each keyboards key-switch stack.
The organs keys do not move when the player is operating.

Each pneumatic primary has a primary valve consisting of a nickel
plated valve stem and a sandwich disk consisting of a thin mica
stiffener between two leather disks.  The leather must have a
relatively high nap so that each disk seats onto its lower valve
surface when at rest, and moves 1/32" when that primary valve is
actuated by the music roll perforations.  Rebuilding these valves with
the improper leather will effectively disable the entire player system
because vacuum will leak out of all of the valves when at rest.

The actual pneumatics beneath each manual switch-stack will probably
have to be rebuilt, too.  Originally, I think these were covered with
organ valve leather, which is widely available but quite delicate,
because these pneumatics are very small.

Only approximately 250 of these curious player organs were built by
Aeolian-Skinner Pipe Organ Company between 1937 and 1939.  They were
designed to keep the industry going during the depths of the
depression, and to permit wealthy individuals to have a player organ
when they couldn't afford to buy a full-fledged pipe organ.  In those
days, the Model BA Player Organ sold for $2,000.00, I believe.  That
was a lot of money in those days.  I hope you find this information
useful in your restoration.

Regards,
Robert L. Baker, Pres.
Electric Orchestras, Inc.