Hi, I have an old Solton M5 and I tried recently to play it, after years since the last time it has been used. The only problem is that the black keys are off tone compared to the white one, but are in tone between them. There's also one more oddity: every A# key is in tone with the white keys (I'm not sure if I remember well, it could also be the D# key). Someone knows what can I do to fix this? The keyboard is otherwise perfectly functioning.
