Hi Im just an old guy trying to repair digital pianos -I have a yamaha clavinova cvp 107 -with a strange problem and nobody seems to understand it -it has led me to try to understand how the cpu is able to interpret the information sent from the key board contact board with just 4 pins providing signal for multiple notes and velocity control to the cpu -I have looked around on the web for this info with no success-I was wondering if some one would be so kind as to point me in the right direction or explain this process /as I do not under stand the signal cpu interface. thanks attached schematics of the relevant areas

 

Hi Im just an old guy trying to repair digital pianos -I have a yamaha clavinova cvp 107 -with a strange problem and nobody seems to understand it -it has led me to try to understand how the cpu is able to interpret the information sent from the key board contact board with just 4 pins providing signal for multiple notes and velocity control to the cpu -I have looked around on the web for this info with no success-I was wondering if some one would be so kind as to point me in the right direction or explain this process /as I do not under stand the signal cpu interface. thanks attached schematics of the relevant areas

The goal of your search is the YMZ702-D chip. That is a high speed keyboard scanning chip. It checks which key is pressed and how far it is pressed (so the cpu can calculate the attack). There is no official datasheet for this chip but someone has done an autopsy of a dead keyboard and figured it out - mostly.
https://paulbanks.org/download/files/ymz702keyboard/YMZ702d.pdf

 

The goal of your search is the YMZ702-D chip. That is a high speed keyboard scanning chip. It checks which key is pressed and how far it is pressed (so the cpu can calculate the attack). There is no official datasheet for this chip but someone has done an autopsy of a dead keyboard and figured it out - mostly.
https://paulbanks.org/download/files/ymz702keyboard/YMZ702d.pdf

thank you so much for your help