I have one of these on the bench now with similar issues. Brass and Synthe 1 and 2 are weak, and the traveler slider has little or no effect. This tells me there's a filter problem. The envelope works on synthe 1's volume, just no filter sweep. I cannot read the chip # for the filter ICs on the schematic-not much of anything can be easily read on it, actually. I have repaired some eroded traces, but some run under 14 pin DIP ICs that I am loth to pull for fear of wiping out a non-replaceable chip, so I am unsure if I got the whole trace right or not. There is output from the synthe and brass sounds, but weak and no filter action apparently. Anybody have a legible PCB trace layout on this beast? IC number/parts list? ANY HELP GREATLY APPRECIATED!!!!