fatar studio 90 reset

[burtnik]

I recently started using a fatar studio 90 that was lying in my friends garage for sometime. I've noticed that some of the keys sound louder than others and in order to produce a velocity of 127 you have to hit the keys incredibly hard, so hard that its only possible if you focus you're energy on one key and really whack it! Controls are minimal, split and transpose up and down. I used other fatars and on them there was always a way to reset the midi using a combination of holding down keys/powering on/off, anyone know if its possible on this model and what the combination is or how to reset? Could be an actual fault with the keyboard, any advice appreciated.