Dear Robbie, permit me to comment on your observations about
Pianocorder System key solenoid electronic parameters.  Pianocorder
System key solenoids receive a fixed 170 Volts DC.  This voltage does
not vary.  So how does the system create dynamic expression if the key
solenoid voltage is constant?

The answer lies in the duty cycle of the 170 VDC supplied to each key
solenoid.  When the solenoids are supposed to play weakly, the DC
voltage spikes are relatively slender; that is, the duty cycle is
attenuated.  When more force is called for, the duty cycle becomes
longer and the spikes become fatter.  The key solenoids play with
greater force.  This has been described to me as pulse width modulation
(PWM).

The Pianocorder System's method of PWM was reputedly one of the patents
held by Marantz which Yamaha Music Corporation was loathe to infringe
prior to their acquisition of all of the patents when they purchased
the Pianocorder Division from the company which bought Marantz' assets.
Thus, Yamaha did not sell Disklavier Pianos in the U.S. until after
they had acquired the Pianocorder Division.

Pianocorder Division did offer a fan kit, but the fan was supposed to
cool the sustain (and soft) pedal solenoids for systems installed in
commercial locations.  In over 22 years of working on Pianocorder
Systems, I have not encountered overheated key solenoids except where
a driver board's output transistor failed to shut its associated
solenoid's power off.  I believe that each key solenoid's mounting to
the massive aluminum key solenoid rail dissipates potentially large
amounts of heat.

There have been over these 22 years several service calls occasioned
by endemic Midwestern spiders and their ubiquitous webs sometimes spun
around the legs of the driver PC boards output transistors' legs.
One unlucky customer was very eager to turn on his recently purchased
Pianocorder System immediately after it had been delivered during
winter.  His home was well humidified and the ambient humidity
condensed on the spider webs spun around the output transistors.  He
managed to burn out around 12 key solenoids, and fried more than a few
TIP 47 transistors, too.

The most frequently affected large solenoids are found inside the P-200
Vorsetzer reproducer.  When these Ledex-manufactured coils fail
(usually due to heat), they simply stop working!

Regards,
Bob Baker