Hi All,  In response to a couple of the recent postings about this
matter, I feel I should clarify some things.  First, the most common
Dou/Art players by Aeolian used a 'push-on front/push-off back' Cherry
switch which is located in the bottom left-hand corner (front) of the
spoolbox.  See http://www.player-care.com/gifs/dou-art-modern-switch.jpg 

Next, if a leak in the vacuum lines which lead to the auto shut-off
valve/bellow was the cause of the problem, the sequence of events would
go like this:  The customer would activate the switch.  The vacuum pump
would come 'on' and stay 'on' until the vacuum level reached a high
enough level to shut the electric switch back 'off'.  Naturally, this
would indicate that the switch is good.

Note that in Gary's initial posting, he says, "In the spool box is an
on-off switch.  When you push the button, it starts the blower and is
supposed to play the piano on electric play.  Right now, the piano only
plays this way if you hold the button in the entire time."

There is also another scenario that hasn't been mentioned, which is not
that uncommon.  Fairly often, people don't read directions even when
they are clearly posted.  In the Dou/Art, the directions for using the
electric pump are posted adjacent to the power 'on-off' switch.  They
read:

  For electric play: for the automatic unit to engage properly,
  attach music roll to this take-up spool and make one complete
  turn by hand.

If those directions are not followed, and the customer simply
connects the end tab to the take-up spool and then pushes the power
switch 'on', the vacuum level in the unit will begin to build up and
the switch will be turned 'off' by the auto shut-off valve/bellows.
That's because the apparatus which triggers the shut-off valve/bellows
involves a lever which rests in a slot in the take-up spool, some
linkage, and a pallet-type valve which resides in the transmission.
See  http://www.player-care.com/gifs/shut-off.jpg 

Note: It's also possible that the unit will shift into automatic rewind
if the music roll paper isn't covering the rewind hole in the trackerbar.

However, in both cases, the electric vacuum pump will stay 'on' until
the vacuum level reaches a high enough level to shut everything down.
Also, as a general rule, the air motor requires more vacuum than either
the auto-rewind device or the auto shut-off device.  So, the possibility
that the air motor will pull the paper over the bar or the required
_one complete turn_ before shut-off occurs, is highly unlikely.  Hence
the need for the Directions.

Regarding the electric 'on-off' switch that's used in the Duo/Art, I've
uploaded two pictures (see links below) which show the original power
switch and a replacement power switch.  In the second picture, you can
see the switch has been taken apart (not broken), exposing the internal
parts.  As long as you have the original switch, you can swap out the
short actuator in the replacement switch with the long actuator in the
original switch.  The job of swapping the actuators takes about thirty
(30) minutes.  (The Cherry switch with the long actuator (push-on
front/push-off back) is not available, and it is my understanding that
those switches were specifically made for Aeolian.)

http://www.player-care.com/gifs/cherry1.jpg 
  (original and replacement switches)
http://www.player-care.com/gifs/cherry2.jpg 
  (inside the replacement switch)

Lastly, I have a small stock of the replacement switches and I have
successfully modified the switch (swapping out the short actuator for
the long actuator) a couple of times.  However, since I don't have
any spare original switches, I would need the original switch to do
the job.

Musically,

John A Tuttle
Player-Care.com
Brick, New Jersey, USA