Misbehaving Yamaha CLP-155. Odd symptom.

by Wiliam
(California)

The E,F, A# and B keys, in all octaves of my CLP-155 only work the first time pressed. Second press, nothing. After a few minutes, the affected keys work again..once.

The rest of the keys work perfectly.

The demo works perfectly.

I replaced the keyboard rubber contactor strip and cleaned the three key contact circuit boards...to no avail...the single keystroke symptom persists.

There are no obviously failed parts on the power supply board or DM motherboard.

I bought a service manual, and am an experienced board-level repair tech, but have no idea what the signal flows are for Clavinovas.

Has anyone seen this single keystroke symptom before?

Thanks for reading this. You are very kind.

William