Casio ap-21 - Key and Button Malfunction

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4. Certain keys do not function
5. A certain key does not function
Replace MA1M PCB.
Do the keys function?
Yes
No
Replace keyboard PCBs.
End
Clean the contact.
Does the key function?
Does the key function?
Yes
No
No
Replace the key contact rubber.
Replace keyboard PCBs.
End
Yes
6. A certain button does not function
Replace CN1M PCB.
Does the button function?
Yes
No
Replace MA1M PCB.
End