Hi Daniel,
I would replace the bad LM3900 if you are certain the output is stuck at 7 volts. Compare the outputs to the other LFO's. Pin 5 is output 1, pin 4 is output 2, pin 9 is output 3, and pin 10 is output 4. If you can find the offending output voltage stuck at 7 volts you have the bad chip. Everything downstream will be 7 volts too. This is what a tech that works on op amps all the time would call stuck at the rails (power supply voltage).
HTH, Fran
P.S. I did not send that other email. Sorry I never replied. We've been busy learning new material plus I've been out booking more gigs. Added some 90's tunes for the millennium crowd..... The Alibi Band