MIDIfying a Yamaha Keyboard (YMZ-702-D)

Picture of keyboard part from CLP-920

A little history

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...


If you find these useful, please let me know on the comments form below!

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Previous comments

  • Armin posted 2016-12-14 21:34:55.591 (182)

    Hi all, based on Paul's description here, I've pubished some more documentation on this with a way to realize a MIDI output for such keyboards. For anyone of interesst, please have a look here: http://elleven.band/midify_ymz702d/

  • Quark66 posted 2014-03-08 01:07:00.0 (98)

    Hi all, especially Armin. Great job with a description of YMZ 702-D chip. I exactly find this info whole day! My last ideas was get info from from repair manuals Yama CLP-8x, CLP9x Px CVP-9x families. But there is only el.schema, not communitacion logic. Many thanks! (I get this keyboard from eBay now and my plan is to build up Clavinova piano. E.g. Atmel reduction into Midi signal and than use old sound unit Yamaha MU90-R inside.)

  • Armin posted 2012-05-28 21:45:21.624179 (81)

    Hi, I just worked on the same issue to adapt a Yamaha keyboard with the YMZ 702 to my own DIY master keyboard project. The information here on this website brings me extremely forward and now I've decoded the communication protocol completely and I've already finished a software for an Atmel AVR controller, which reads out the Yamaha keyboard, sends the data over MIDI, merges any MIDI IN data to it and provides 4 different velocity characteristics. The MIDI channel for the note events is also selectable. If anyone is interested, please contact me using the contact form of my website http://www.elleven.de/en/ Thanks a lot to Paul Banks for the provided information here on his website - great!!! Regards, Armin

  • Colin posted 2011-12-06 17:07:51.252323 (69)

    I have just got an 88note hammer action keyboard(GH88) from a CLP130 and would love to convert it to a midi controller keyboard,can't wait for an update

  • Matt posted 2011-10-15 06:55:54.834081 (65)

    Any update on this? I just got a clp 930 keyboard [just the keys] and it has all the circuitry up until right after the IC. I am looking to convert it to midi. Thanks!

  • ricangus posted 2011-01-11 14:21:16.757577 (23)

    hi, I am a electronic music repairman. I have some keyboard like this, i am so interresting to transform this keyboard in midi keyboard to control expander. cya ricangus