Step 1: Find a synth that uses that particular keybed (maybe Kurzweil?)Step 2: Get the service manual for that synth.
Why not just use the midi output the Fatar keyboard already provides? That is a nice midi controller, I hope you haven't butchered it.
I guess we have something different. I think ours is full 88 keys and weighs a ton as I recall. Very nice piano action feel, my wife learned to play on it for several years until she decided she needed a real piano for the more subtle feel a real piano offers.I think it's this one, I got it used at Guitar Center quite a while ago.http://www.studiologic-music.com/sl-990-pro.htmlWhat kind of parts are on the electronics board?