Follow-up: Mysterious unsolvable Yamaha double-striking uprights

[Geoff Sykes]

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Greetings all --
=20
Here is the response I got from David Durben at Yamaha. I plan on doing =
a
couple of the suggested tests so that I can learn from them, but my =
guess is
that since this is occurring on a number of pianos the double-strike =
that I
am experiencing should be considered acceptable behavior. When you think
about it, it really is occurring during a slow movement that is "outside =
of
normal playing conditions."=20
=20
-- Geoff
=20
In this case, the first thing I would mention is that we need the piano =
to
play correctly under normal playing conditions. As you know, when we =
piano
technicians are working with a piano, we often will cycle the action =
slowly
enough to have "malfunctions" occur, which would never occur under =
normal
playing conditions. We need to be sure that this is happening under =
normal
playing conditions, and if so, I have some suggestions.

First of all, I would want to be sure that the keys are traveling the =
full
10mm distance (with about 250 grams pressure). Then of course, check =
that
letoff is 2mm in the treble, graduating to 3mm in the bass (this looks =
very
deep, when compared to the 1/16 or 1/8 inch measurement that many of us =
have
become accustomed to). If these factors are correct, I would next test =
the
offending keys with the damp pedal engaged. If the problem disappears, =
we
know that the damper return springs are a little too stiff, and we will =
want
to carefully ease those off. If that still does not eliminate the =
problem
(or if pressing the pedal made no difference), we need to check the =
hammer
return springs, to be sure that they are set strong enough to do their =
job.
Again, be careful, use samples, and make any adjustments as evenly as
possible.


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