Yamaha CP33 Sound Problem

Synth Repair
1

I have a Yamaha CP33 that has developed strange sounds on the top 19 notes. They sound faint and have a percussive sound, rather than the piano sounds that the rest of the keyboard has. This is also not uniform for all notes. Could this be a Main Board issue? I did inspect the rubber pads and there is no problem. Is there a coin cell battery somewhere? Is it possible to perform a factory reset, and how?

I also tried the MIDI out with another synth with the same results, and did notice that the top octave seems to be repeated an octave lower. Thanks for any help. GCH

2

I discovered the reset trick - " To restoring Yamaha CP33 to it’s factory settings, just simply power ON while simultaneously holding the “Rightmost White key (C7)” and “Three Black Keys (F#6, G#6 and A#6)” until “CLr” appears in the display."

3

That change nothing. GCH