I suspect there are leaks.  Many small leaks add up to one big leak,
and there are literally hundreds of places that might leak.  Each one
should be tested.  Test:

1. Place masking tape over the tracker bar.
2. Set lever to play position
3. Set Tempo at 75, because the air motor uses a lot of vacuum and the
   following settings will be incorrect if the tempo is set at zero.
4. Turn on motor

5. Temporarily (for testing) remove hose 1-B and 1-T directly from each
   of the two crescendo devices, to allow them to collapse fully.
6. Set modify switch at "Medium".  The Medium setting _must_ be correct
   before adjusting the Brilliant setting.
7. The vacuum reading should be 20".  This is set by slightly rotating
   the pump spill valve spring (this is the longer spring closest to
   the amplifier pneumatic).  Vacuum gauge reading should be taken in
   both bass and treble.

8. Next move the modify switch to "Brilliant".  Does the Amplifier
   pneumatic on top of the pump close to the limit screw setting?
9. The vacuum gauge reading should be between 27" and 30" (the limit
   screw on top of the amplifier pneumatic adjusts this setting).

10. Manually press down on the amplifier pneumatic.  If you cannot get
    a reading of at least 27" with these tests, then there are leaks.

Most leaks occur in the unit valves.  The "clamps" that hold them
in place exert so much pressure on them that when the wood expands
during changes in humidity, they compress, causing tiny splits in
the sides of the valve blocks.  If they are minor cracks they can be
sealed with burnt shellac.  However, if cracks are severe, the valve
should be rebuilt.

Other leaks can be in the expression units themselves.  The cork
gaskets on the intensity valves often loosen during very dry
conditions, and require very slight tightening so the intensity
valves will work properly.

I suggest that all owners of the model A Ampico replace the old
model A unit valve "clamps" with model B spring clamps.  The model
B spring clamps allow for expansion and contraction.  The model A
"clamps" will eventually damage the unit valves.  Ampico knew this,
and that is why they replaced them in later model players.

In addition, the Bakelite valve seats become loose, and need to
be removed and resealed with burnt shellac.

The pump itself could leak.  It could be worn out, or have been
recovered with faulty bellows cloth.

I had one case where a hose controlling the Subdued become
disconnected, therefore the subdued was activated even though the
Subdued switch was set in the "Off" position.

One widely overlooked spot to check is the function of the amplifier
control block.  Often the small valve fails to seat properly, which
in turn prevents the amplifier pneumatic from closing.  Remove the
amplifier control box, and test it.  The valve should seat perfectly.
If not, the problem can be solved by removing the valve stem and
placing a small piece of thin felt between the valve stem and valve
button, allowing it to wobble slightly.  This allows the valve button
some freedom of error, and it should seat properly 100% of the time.

The biggest problem for all players is a _wide_ swing in the percentage
of relative humidity.  I do not have much faith in electric devices
placed inside or under pianos to add or subtract humidity.  I find it
far better to control the humidity of the entire room in which the
player is located.

I have told this many times, but few listen.  I will repeat: If you
will keep the humidity _steady_ year round, in the room where the
piano is located, it will solve more problems than you can imagine.
I suggest all owners of pneumatic players obtain an inexpensive
humidity gauge, and keep the room humidity steady.  35% would be ideal,
but steady is more important than an actual percentage.

In my home, where the humidity can increase to 90% in summer and dip
to 16% in winter during the heating season, controlling the humidity
presents a big challenge.  This may involve indoor climate control,
by obtaining a room dehumidifier for use in summer and a humidifier for
winter, and keeping the doors and windows to the room where the player
is located closed at all times.

Bruce Clark