Greetings,  I am working on a 1927 Half Duo-Art (Stroud or Steck).
At some time in its past the foot pump was removed and an old
belt-driven electric pump installed.  After rebuilding the accordion
pneumatic and bench testing the unit, it became evident that the only
time the accordion unit has any effect of the base and treble is when
the Bass and Treble Manual Accent Levers in the key slip are held in
the "soft" position.  Normally they are held in the "loud" position by
springs in the linkage under the key bed.  These levers operate sliding
valves in the expression unit that lay over a tapered slot similar to
what is found in a typical wind motor governor.

After exploring the MMD Archives, it became clear that the Half Duo-Art
was not meant to be operated by an electric pump because the pump
provides a continuous vacuum of say 20 to 30 inches of water which is
unregulated.  This would explain why the hammer were so deeply worn.

The owner would like to keep the electric powered motor and pump unit.
Is there any good way to make this setup work in a satisfactory way
that gives some control to the player?  What if I simply reversed the
springs on the Bass and Treble Manual Accent Levers so that their
stationary position was at "soft".  Any help would be appreciated in
this latest adventure.

Sincerely,
Joel Cluskey - Cluskey's Piano Works
Pittsburgh, Pennsylvania