MOTM

Folks, I just finished building a MOTM 300 VCO.  I have a problem.   the EXP/LIN switch is not acting correctly.  When I have a LFO control voltage in FM1 the oscillator appears to work fine when the switch is in the LIN position.   When I switch it to EXP, the oscillator will does not react, the oscillator acts as if nothing is inserted into the FM1 jack.

I am an experienced builder and I have built MOTM 300's before. I know I can email Paul S. on this, but I wanted to hit the list first to see if anyone had any tips on where I might look for an issue.

Any thoughts on what might be the problem and where I can look?

Thanks
Andy Miller