WANTED - PR603M amplifier circuit board

Hi there.
I have a PR603M with amplifier issues. I've had it repaired three times, but each time it works well for a couple of weeks and then the original problem returns. Just wondering if by some miracle someone has an amp board that will fit (possibly from the PR703 as well, not sure if they are compatible). Maybe someone has a PR603 where the main board has gone and they want to get rid of the piano?
Any help or suggestions greatly received.
(I'm currently using a separate amp via headphone socket so can still use this wonderful instrument.)
Many thanks.
Phil.
Derbyshire.