Leonardo Forti wrote in 090301 MMDigest:

> One of the valves has an external nipple stopped by a rubber
> tube with a screw in it.  What's that?  Is it original?  Only
> one crescendo speed seems to work.

Mr. Forti,  The Ampico crescendo mechanism you describe is incorrectly
blocked with the screw mentioned.  The screw is _not_ original.  Your
crescendo is not functioning correctly because of the screw blocking
the air supply,  Remove the screw and discard it.

This rubber tube is a not supposed to be blocked, or attached to
anything.  Its purpose is a "breather" and muffler for the valve system
inside, which is always pulsing and ready for a signal from tracker bar
ports #1 and/or #5 (for either Treble or Bass Crescendo).

There are two small nipples on the side of the crescendo.  They should
be marked 1-B & 5-B, or 1-T & 5-T.  Both the bass and the treble
crescendo mechanisms are identical.

With vacuum applied to the _large_ elbow on the top of the mechanism,
test 1 & 5 separately:

  #1 open by itself is a slow crescendo;
  #5 open by itself is a fast decrescendo;
  #1 & #5 open together is a fast crescendo;
  #1 & #5 both closed is a slow decrescendo.

At rest, there should be a faint pulsing sound at the end of the
muffler tube.  This is normal.

The screw that adjusts the spring tension is the setting for the lowest
level of intensity.  It should be set as low as possible, or low enough
that on very soft passages in the music, the notes are very soft but
not dropping out.

The average vacuum measurement of first intensity is between 5" and 7"
water gage suction.  This should be equal in both bass and treble,
according to factory specifications.  (My own preference is to set the
bass 0.5" higher vacuum than the treble to compensate for the heavier
hammers.)

It is very important that there are no leaks in the bellows cloth or
gasket and the valve travel is correct.

Bruce Clark