A few months back I gave a keyboard lesson to the fellow who purchased my PSR-S910. It turns out that he's a computer engineer who sidelines as a keyboard specialist. He knows how to repair motherboards and all sorts of stuff. Apparently people have sent him keyboards from all over the world when a replacement motherboard was too expensive or not available.

Anyway, here's his Facebook page. https://www.facebook.com/KeyboardSpecialistChicago