Vintage Synth Repair

Hello,
I bought a second hand poly800II and some time after playing it I noticed 
that its frequency values are out of defaults.
I believe that the guy i bought has changed the values on the board inside 
(VR2, VR3, VR4 VR5)
First it was detuned and i had to make some changes inside, in the green 
board to make it get on tune, but cutoff, resonance seem to be
Is there any way i can calibrate it again???

thanks
italo
italo@...