In response to D. L. Bullock's question in MMD 030405, I have slightly
changed the subject by inserting "A" behind the word Ampico, and offer
the following.

While Robbie did reply correctly to the question based on his
understanding that D. L. Bullock was referring to an Ampico B, this is
not what D. L. Bullock was asking.  Yes, the Ampico A does have, on
some models, special valve blocks that vent the stack.

I can describe my observations and conclusions drawn.  Ampico did place
special valves on the stack: one on the treble and one on the bass.
These valves are modified secondary valves and are placed on blank
spots on the stack.  When the valve is triggered, it opens the upper
hole, the one that normally goes to a striker pneumatic, to the
atmosphere.  These valves are triggered during rewind.  They are tubed
to the primary valve that controls the pump cutout pouch.

The theory is that these valves will immediately equalize the stack
pressure to atmospheric anytime the reroll mechanism is engaged.  Why?
If the stack is tight enough, if the reroll perforation is too close to
the last playing notes, the piano can actually play, in reverse, the
last few notes on the roll.  A secondary function could possibly be to
keep the notes silent if the pump cut out leaks during reroll.

The installation of these valves was really unnecessary, as most Ampico
A's do fine without them.  On a personal note, I have had freshly
rebuilt pianos that do play one or two notes in reverse on reroll, when
these valves are not present.  The down side of the presence of these
valves is that they "rob" the power of the pump cut out primary during
play, and if other system leaks are present, the pump cutout pouch can
"sing" during play.  This singing occurs when the pump cut out is not
fully open during the "play" mode.

So after a long discussion, the short answer is:  tube them to the pump
cut out primary and hope that the cut out pouch doesn't "sing" during
play.  There should be no comparison of these valves to those found on
the Ampico B as the intended function is entirely different.

Bob Taylor