If you probe pin 28 of the FV-1, do you have anything there?
Doh, Jwin615 beat me to it.
If you do have something at pin 28, then keep working downstream from there to the output to see where wet's getting dumped.
Got signal at the TL072's pin 5 and 7? Yes?
I'd suspect the MIX pot, legs 2&3 look like they could use re-flowing the solder.
Check pins 26 & 27, in the photos it looks like a possible short there, but that could be a trick of the light.
If No signal coming out of the FV-1 pin 28...
then do you have signal going into it? Check pin 1 (and 2).
Definitely seems like a job for an audio-probe and work your way through the FV-1...