[ Ref. 230729 MMD, Odd Action Stack Valve in Late Ampico 'A']

John Tuttle asked about the spill valves located on some Ampico stacks
[230729 MMDigest]. I always thought they were in late actions only but
I have a 1920 model with the feature in an upright so they thought of
the idea early, it appears.

The two spill units are located in the bass and treble at a blank spot
like a break. They are then connected to the universal vent block that
controls the pump cut-out.

The valves are modified in various ways to let them spill. In the
photos it is seen that someone filled the little gouge in the top of
the valve thinking they should not be that way. They should be open
there so the valve vents to atmosphere when the pouch is vented by the
cut-out valve block venting the cut-out pouch.

Their function would be to let the stack vent on re-roll in the event
the pump cut-out does not fully close and allow some vacuum to get into
the stack, making the notes maybe play on re-roll. I do not recommend
using them as they would cause catastrophic stack leakage should they
somehow get vented on play. It is up to you, however, to do as you wish
with them.

There are people, it seems, that like to say Ampico actions are of
"this type" or "that type" of something. It is better to understand
that Ampico was an innovator, and they refined their product over the
years and made many changes in their actions, both large and small, in
the ten or so years between 1919 and 1929.

Hope this helps,

Ben Gottfried - Ben's Player Piano Service
Richfield Springs, New York
https://bensplayerservice.com/