Recently I had the Ampico treble crescendo unit fail.  It became
sluggish and erratic, but specifically failed slow crescendo.  It turns
out that valve that was affixed to the stem with a tiny brad had torn
loose from the stem.  Clearly the mating surface between the brad and
the leather valve face was so tiny that the forces would have been
high.  There is not enough surface area on the head of the brad to
distribute the forces.  The aged leather failed.

But the point of this posting is the hair spring that is wound loosely
around the valve stem to help push the valve up to its closed position
(it pressed against the inflated pouch and against the valve face).
This pushes the valve in the same direction as the inflated pouch.

Nowhere in published pictures of the unit does it show the hair spring.
I'm wondering if this is seen in other Ampicos.

Bill Chapman - AMICA Memberships
in sunny, breezy Palm Springs, Calif. area