Vintage Synth Repair

hi
i have received a korg polysix, it's in good condition but when i 
plugged it and turn it on, everything works except filter and VCO
1-the cutoff and resonance don't work
2-the vco doesn't match the change of tessiture ( 16', 8' 4' or 2')

for these two point do you know what is or are the componant to be 
change on the board KLM

regards for all
Florent