I just picked one of these up for pretty cheap, and have been cleaning it up and working on adding all the great mods for this synth. Everything works fine except for a popping sound on fast attack and decay (goes away with longer attack/decay settings on contoured), a hissing sound as the cutoff is reduced, and the emphasis is barely noticeable. Now, of the things I have checked:
-OTA CA3080 is fine. Have tested multiple with no change. This was my first plan of attack as I found this website: http://www.arcfn.com/2010/03/fixing-my-concertmate-mg-1-synth.html
-Emphasis AMP 741 is fine as well. Tested multiple also.
-Replaced all electrolytic caps.
-Tested matched transistor IC CA3046N. Diode test seems fine.
-Discreet filter transistors Q1017-Q1022 test fine in circuit.
-VCA Balance trim seems to have no effect.
-Voltage to the LF353N buffer seems fine.
-Voltage through cap C23 - which charges up to 6v on attack and back down to 0v on decay - seems to have a constant output of .18v. Old cap and new test fine.
-All resistors/diodes test OK, but I have yet to get the replacement sliders in the mail. Reading through the service manual it says that it sums the voltage through many of the sliders at once. Could low operational resistance add up over several sliders? I can upload schematics/pictures if necessary, and I will update when I install the new sliders. Any help would be great, thanks!