Yamaha Disklavier E3 Series Maintenance Handbook page 28

B. Adjusting the Key Sensor Unit
When shipped from the factory, the key sensor unit is adjusted to the following
positions and measurements.
Clearance does not require adjusting under normal circumstances. However, when the
unit is replaced, etc., the measurements should be adjusted to those given below.
Position: Clearance between the bottom of
the keyboard and the top of the key sensor
unit chassis when the black keys on each
section are fully depressed.
Basic dimensions:
Clearance 3.8mm to 4.0mm (ａ).
Adjustment: Use the screws (1 each) on the
front and rear of the sensor unit brackets
(4 locations) to adjust (※①).
Align key sensors so that they are parallel to
the keyboard.
When the clearance between the key sensor and the keyboard is too wide
 the key shutter will not be able to break the light beam.
When the clearance between the key sensor and the keyboard is too narrow
 the keyboard will come in contact with the key sensor when played hard.
Sensor measurement with the service center mode is required not only when replacing
key sensor units, but also when carrying out keyboard height adjustments and other
keyboard related adjustments.
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