Some time ago my Yamaha CLP-920 piano developed a sticky keys fault. At first, this was just a minor irritation but as time went by, more and more keys started to stick to the point where playing it was difficult. I tried moving the sticky keys to less used parts of the keyboard and this worked for a while but eventually the newly placed keys started to stick too.
An Internet search revealed that this was due to a manufacturing issue. The wrong type of lubricating grease was used on the keys and it was eating into the plastic. Eventually, the plastic became weak and broke causing the keys to shift slightly and rub against the rubber stop of the keyboard.
I asked Yamaha for advice. They immediately recognised the problem and, despite the piano being out of warantee they offered a free repair. This is really an excellent service.
After the repair I was left with a spare keyboard and the geek in me couldn't resist putting a power supply on it and probing about.
Skip to the download section for an unofficial "datasheet."
The IC which does the keyboard scanning is a YMZ-702-D. There appears to be no datasheet for this part and as of today my emails requesting information have been un-answered. I guess it's a proprietary part of theirs. So I put the results of my probing into an unofficial datasheet - hopefully that will help with anyones projects.
Watch this space. I have run out of time for now...
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