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MMD > Archives > July 2009 > 2009.07.23 > 05Prev  Next

1970s Aeolian Player Piano is Leaking
By John A. Tuttle

Hi All,  The plastic block valves that Aeolian made are a central
problem to the performance of the player system.  The valve clearance
is much too wide, and the absence of any filtering at the exhaust port
is an open invitation for all sorts of debris -- animal, vegetable,
and mineral -- to enter.

Furthermore, the pouches were not well dipped, and they have a bad
habit of shrinking as they age.  The combination of these two problems
creates a situation where the exhaust valve facing doesn't always seal
when a note is played.  The problem is even greater when numerous notes
are played simultaneously.  In my experience, it only takes three bad
valves to drag the performance of the system down to "poor".

Locating these errant valve blocks can be somewhat of a pain because
they are more apt to malfunction when the vacuum level reaches a
particular low point.  When you test the system with a test roll,
playing one note at a time, the blocks tend to work fairly well.  For
that reason, I always test the notes at the lowest volume setting.

One other problem happens because of the vacuum losses that occur
during the transit time as the valve changes state.  Those losses
adversely effect the entire system and can cause uneven playing volume
and missed notes.

Two more points of interest concern the trackerbar tubing and the air
motor.  First, it's not uncommon for particular notes to quit working
because the trackerbar tubing is pinched somewhere between the
trackerbar and the block valve.  The areas that are most problematic
are where the tubing passes through the keybed and the areas directly
beneath the metal tubing holders.

Secondly, the most common leakage problem I've noticed with the modern
Aeolian players involves the air motor.  The leakage is generally
internal, but the sliding valves are also a problem.  The internal
leakage can be eliminated by sealing the main vacuum channel with
Phenoseal (see link below).  The sliding valves typically need to be
resurfaced to reduce the leakage caused by warping.

Replacement valve blocks are available at 

Phenoseal is available at 

John A Tuttle
Brick, New Jersey, USA

(Message sent Thu 23 Jul 2009, 21:59:01 GMT, from time zone GMT-0400.)

Key Words in Subject:  1970s, Aeolian, is, Leaking, Piano, Player

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