2) Place a 1,500 gram weight on each key in sequence and note the keys that give the lowest (the low weight key) and highest (the high weight key) impedance values. Mark these two keys (with tape, etc.).
General standard: The low weight key is a white key and has an impedance value of 3 ohms or less.
The high weight key is a black key and
has an impedance value of 500 ohms (+10%).
3) Connect an oscilloscope to KLM-759 CN21 1-pin (output) and 3-pin (GND).
Connect to CN23 which was previously disconnected.
4) Place a 500g weight on the front of the low weight key found above.
Adjust VR1 so that output voltage crosses the OV line (rising from – to +) within 2 to 8 seconds of loading the key with the weight.
(Threshold voltage level adjustment.)
5) Next, put a 1,500 gram weight on the front of the high weight key and adjust VR2 so that the output voltage crosses the +3.SU line within 2 to 8 seconds of loading the key with the weight.
(Buffer amp gain adjustment.)