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Kawai CL20R repeated key not working

We purchased a second hand keyboard with some non working keys. My husband works with electronics. We pulled it apart and cleaned all the contacts but then found the not working keys are the same repeatedly all the way up the board, the last one on every line of the grey silicone bubbles sections that compress onto the carbon sensor. We checked all the diodes and the cable that connects into the motherboard and they are all working. Any other ideas?
thanks so much.

torokj picture

Hello Amanda,
The cleaning sometimes is  not enough,the graphite-rubber  layer loses his conductivity.
I would check it first with DMM (few kiloohms) 
Maybe this type of conductive pads would help (cut the original and replace with a silicone base glue):
Good luck to repair!


Sakos2 picture


I suspect a different root cause, because this device has touch-sensitive keyboard (and not simple pushbuttons like a tv remote) furthermore the issue affects a group of keys systematically.

Do this: Press and hold a working key. Wait the sound fade out. Then without releasing the key test if the same key one octave above or below is producing sound or not. If not, then you have chance that one of the keys in the non working group got stuck and blocks the others.
So, I would check the resistance of the sensors against abnormal values, mainly short circuit. If they seem OK then I would check the keyboard scanning lines with an oscilliscope.