Yamaha CS80

Dear CS-80 friends,

i am currently restoring a CS-80 which collected dust for some 10+ 
years in a warehouse. Fortunately everything seems to work so far, but 
of course the tuning is a bit off.

When starting the tuning procedure i cannot go beyond step 2. According 
to the manual Value at pin 13 of IC2 KAS board should be set to 125mV. 
Mine stays always at 135mV- no matter how i turn the corresponding VR1 
pot. VR1 pot itself is ok though.

Anybody has a hint?

Thanks, Gregor