Frank Himpsl mentioned that his Ampico expressions seem to "lock on" and
stay locked if he starts an 88-note roll with the automatic switch to "on"
then depresses the two manual buttons and leaves them depressed while
turning the automatic switch to "off."  An interesting anomaly.

The only thing the automatic switch does is operate the expression cutout
strip.  When it is "off," the cutout pouches in the strip close off the
ports to the expression valves.  The two manual buttons slave proportional
cutout pouches. To whatever degree they are depressed, the pouches follow.

If the buttons were fully depressed, the pouches follow the buttons,
automatic or not.  So "tricking" the expression by switching off the
Ampico automatic switch with those pouches closed should not change
anything unless something else is causing the pouches to stay positioned,
or several cutouts in the expression cutout strip are not closing off.
That allows some expressions to actuate but not cancel, perhaps. Once
they are up, they stay up.

Craig Brougher

 [ My Ampico B had similar anomolies before it was rebuilt.  I think
 [ that when the vacuum rises slowly, as when the motor is turned on,
 [ the valve logic doesn't "follow the normal rules." -- Robbie