Roland EP 77 key contact problems

[Rdartist]

There are 3 keys which are not working under normal playing pressure. If you hit the keys very hard it will sound. I've cleaned the contacts, swapped the keys from other sections and swapped the rubber contacts from other sections yet the same 3 notes don't play while the other keys work in the swapped sections. Any clues or hints?

[Jazz P Bass]

Have you cleaned the circuit board underneath the rubber contact.
Alcohol seems to do very well.

[Rdartist]

I cleaned the circuit board with alcohol. That is what I meant to say when I said I cleaned the contacts.

[Jazz P Bass]

I have used a pencil eraser already (gently), if the pcb contact is really black.
Then denatured alcohol.

[diydidi]

Check for cracked traces/ pcb