One final problem I've been having with this synthesizer restoration project for a friend.
I've reassembled the synthesizer and noticed that the membrane switches on the front panel weren't functioning properly. I traced it back to a certain connector on the board - when I tug upwards on the wires leading to the header the buttons function normally, but when I relax them slack and let everything rest normally the buttons stop functioning again.
I've lifted up the board and tested continuity between the soldered PCB pins and the points where the wires from the membrane button board enter the detachable header while connected and everything tests fine, so I'm not exactly sure what the problem is...