Vintage Synth Repair

Hi everybody,

I know this is not about a vintage synth but it could be useful.

I'm trying to fix a old Roland HP-5000SL digital piano that a velocity problem on one note even after the rubber key contacts have been replaced and the contact strips have been cleaned. 
I think the contact strip (board) is worn.
Those boards aren't available from Roland anymore.

Is there any way to refurbish the carbon contacts on those boards?

Thank you!

Nicolas