Disklavier

I'm taking the liberty of quoting (under fair use, I hope) from a Yamaha 
maintenance document.

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. . .   The core
plungers of the pedal drive units are not
separate items, but instead, are built into the
traditional pedal system, and the plunger
moves each time the pedals are moved. It is
fairly easy to see that a solenoid has to have a
certain opening or "gap" while at rest to provide
the correct amount of movement when the
current is applied. For example, if the gap is
less than it should be, the amount of travel of
the solenoid plunger is decreased by that
same amount, and might not be enough to
move the pedal action to the correct position. It
could also close completely causing a noise as
the solenoid core reaches the end of its travel.

Another issue is that by its electrical nature, if
the solenoid core is stopped before the job is
completed, the computer will continue to send
extra current trying to get the job done. This
extra current causes the temperature of the
coil to rise, and could shut down the entire
system rather than overheat. It is obvious that
the solenoid needs to have a specified gap at
rest to function properly.  . . .

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Thus, too small a solenoid gap could result in a thump when the pedal 
goes full down--both when being played or during reproduction.  The 
adjustment of the gap will require the tech to find or make a gauge and 
to get down on the floor with the gauge, a pair of wrenches, and perhaps 
even a penlight.

That gap, if misadjusted, however, could not account for the thump when 
the pedal is released, which probably comes from 88 dampers 
simultaneously striking the strings and abruptly transferring energy 
from the damper mechanism's fall.

The broad principle is standardization--all DKVs ought to play in the 
same manner.  That's why pedal regulation ought to be checked and 
adjusted before before trying to compensate with MIDI pedal values.

-- 
Robert Welcyng
Anchorage, Alaska