Regulating the Duo-Art is not an easy task. It is a nightmare for the
inexperienced technician. The probability of this thread helping solve
the problems discussed in the last few days is quite low. Even so,
I will make a few general comments.
First, the accordions are only bench set at the binary gap scheme given
in the literature at 1/16, 1/8, 1/4, and 1/2 inches. Once the test
roll regulation begins, these gaps must be "tweaked".
Second, the "Play/don't-Play" sections of the test roll are not 100%
reliable. In other words, just because the piano performs these test
perfect, it doesn't mean regular performance rolls will sound correct.
There must be further tweaking and hundreds of rolls played to get it
In both the examples recently given, I see a several common possible
deficiencies. They are:
1. Leaking knife valves (indicated by rapid increase of vacuum
2. Weak pump or general leaks (indicated by low maximum vacuum,
3. Spill valve setting too high or incorrect operation
I hope this helps. Keep in mind, it is a very big jump from the
mechanical adjustment to the musical performance.