Hello Everyone,  Over the weekend, I was giving my late Ampico A
a once-over (tightening the long stack bolts, running the test roll,
etc).  In the course of the test roll I discovered that the treble
side slow crescendo was not working properly.  With a gauge, I tested
both sides of the stack and everything was fine: just about 6, 20 and
30 inches (for 1 intensity, medium, brilliant) on both sides, using the
expression buttons.

All of the other tests on the test roll seemed fine except for the
slow crescendo on the treble side.  The slow crescendo would only raise
vacuum to about 13" then return to 6".  The fast crescendo, however,
was fine: at medium it increased and decreased from 6" to 20" and back
to 6" at the appropriate speed.

With tape over the tracker, I removed T-1 and watched the crescendo;
it did not close all the way.  I removed T-1 and T-5 and it closed
completely and stayed closed.  Likewise, when I pressed on the pallet
valve, the crescendo closed completely.  However, if I removed T-1 and
T-5 together, and put back only T-5 leaving T-1 off, the crescendo
would not stay open at 20", but close again to about 12".

Suspecting a possible leak, I double- and triple-checked the expression
pneumatics and connections, re-measured the span and collar of the spring
pneumatic and checked for air-tightness, checked the crescendo bleeds,
likewise checked the spring pneumatic connections to the crescendo;
everything appeared fine.  Likewise I checked the crescendo itself for
leaks but didn't find/hear anything.

All of the cut-out and drawer connections are fine, the expression
buttons work fine; Ampico on/off works fine, too.  The T-1 adjusting
screw is at about half and the T-1 setting is good for repetition and
volume.  The piano was restored within the last 15 years and the
workmanship overall is top "drawer" (Ampico; get it!).  To the average
listener, the piano plays fine and sounds good; however, there is
clearly something wrong that I'm not finding.

The bass crescendo works perfectly and I know I had tested the treble
crescendo within the year and it worked fine last time it was tested.
Any advice would be appreciated.

Adam Aceto