Greetings,  The 80 inches vacuum that Tim Baxter referred to on his
piano may have been misunderstood.  Tim was referring to the maximum
vacuum with the spill fully closed and the crash operating, but with
just a single note playing.  If the stack is tight (and it should be
under that vacuum unless it is a leaky mess), under these conditions
the vacuum will rise to the pump maximum.  If the valves in the pump
are good this will be a very high vacuum.

80 inches vacuum is not unusual.  This sort of vacuum will rarely
happen in playing, which is fortunate, but an electric valve system
must be able to handle this vacuum to play a Duo-Art under all
conditions.  Even without a crash setting on the accordions, the pump
pressure will rise this high when the spill is closed and no or few
notes are playing.  The theme primary suction is right from the pump
so the vacuum rises this high at the signal tubes to them.  That is
one reason it is difficult to design a cool running e-valve system
for the Duo-Art.

Best regards,
Spencer Chase
Laytonville, Calif.
http://www.spencerserolls.com/

 [ Wayne Stahnke built one or two special IMI Cassette Converters
 [ in the late 1970s for installation in Duo-Art pianos, and he
 [ experienced the same heat problem you mention.  Fortunately
 [ there was room to install a larger power supply plus a blower
 [ to cool the power supply and the magnet valves.  -- Robbie