Yamaha disklavier MX-100A, Service Manual

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Explanation of Sensor System
The sensors on the DISKLAVIER are as follows:
• Key Sensor Unit···Optical Sensor···Detects key information.
• Hammer Sensor Unit···Optical sensor···Detects key information.
• Pedal Sensor Unit···Mechanical sensor···Detects pedal information.
1. Key Sensor Unit, Hammer Sensor Unit:
The Key Sensor, Hammer Sensor Units include the following equipment:
• Light emitting element···LED
• Light receiving element···Photo-diode (PD)
• Key detection element···LSI KAPP (YM2019)
• Conductor···Optical fiber, sensor head
• Shield···Shutter
Information is obtained by using a shutter to "Cut Off" the path of conduction for the light.
For each key there are three sensor heads, one on the keyboard (K) and two on the hammer (M1, M2).
The unit is constructed in such a way that the light will be blocked when (K) is located 4.5mm from the
start of keyboard depression, when the distance from the hammer tip to the string is 10mm for (M1),
and 1.5mm for (M2).
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