Having spent a good deal of time rebuilding my 1928 Marshall and
Wendell Ampico in 1981, I recently spent a lot of time re-rebuilding
it. I have rebuilt the primary valves and completely rebuilt the
expression devices, intensity control and crescendo units. I replaced
pouch leather, rubber cloth, gaskets, valve facings in toto on all
units. The beauty of the Ampico is that if everything is rebuilt,
everything should just work, but my crescendo units have the following
At zero level (all intensity levels cancelled) the crescendos
(particularly in the treble) just sit there and barely flutter.
The "flutter" is the unit in idle mode awaiting something to take
place, as I understand it, i.e., when the intensity level is raised,
or a demand on the vacuum by notes playing, or a crescendo hole opened
by the roll.
When the slow crescendo hole is opened, the slow crescendo valve,
(which is normally fluttering owing to the pallet valve and spoon
arrangement) should then seal as the crescendo bellows is exhausted.
Mine seems to engage only _barely_ and never really moves much.
My understanding is that the crescendo pneumatic should travel its
full distance (yes? no?) in 11 seconds. When the fast crescendo port
is opened and the bypass is opened, the device _does_ collapse in about
4 seconds, so there is sufficient supply to collapse the unit from the
Question: If there are no intensities set (the cancel has zeroed out
everything), will the crescendo bellows collapse the entire 11 seconds
and raise stack pressure to loud playing? Or is it merely a bridge
between levels of intensities?
I would very much like to speak with someone who has done a number
of these units, as my general knowledge of the minutiae of Ampico is
relatively nil. I know how to cover pneumatics, rebuild valves, set
travel, etc., but the specifics of Ampico trouble shooting is little
known to me.
Fort Worth, Texas