Yamaha CS80

This is a big question here. The CS-80 I'm working on will barely change pitch all the way up 
the keyboard now. Some keys will play a little lower but not much. Now here are the 
symptoms:

I replaced most all the IC's on the sub board. I replaced the entire KAS board with a working 
one. Problem does not change.

The pitch ribbon is having no effect on pitch. Neither is the pitch knob.

The channel 2 detune IS working as is the footing sliders.

Ring modulator is working, sub oscillator is working and so is all the waveforms.

Any of the tech guys able to help?

Thanks!