Vintage Synth Repair

Hi group,

I'm currently restoring my whiteface Odyssey. I tuned it up (PSU, A and B boards), changed a few tantalums and changed the LM301 driving the filter. 

However, there is something weird in the filter section; the driving voltage (which should be negative according the service manual) is always close to 0 (ADSR moves it a little bit). And the filter itself is always closed: to open it up, I have to set KBD CV, LFO and ADSR control voltages, as well as CUTOFF at max.

I removed the filter and checked the output of the LM301; seems good but does anyone knows what voltage range I should expect out of the LM301? 

Any advice to test the 4023 filter module?

Thanks,
Francois