Discussion about the Korg PolySix synthesizer

That sounds like a lot of work. “no cables are modified”? To put it back the way it was, you would need to unsolder all the black and white wires from the midi board and solder them in the correct order to the key contact circuit board on the bottom of the keyboard, which also means unsoldering all of the red/black or orange/black (colors are hard to tell in the video) that are currently soldered to the key contact board. How about unscrewing the midi board and lifting it up to isolate it from the foil shield below? Does that make any difference? The way it makes more noise when the metal keybed touches the foil shield could be a ground loop or it could mean something is connected to the foil that shouldn’t be, so it is acting more as an antenna for noise. There should be no connection between any of the red/black wires and the metal keybed. The only connection to the metal keybed should be when it touches the foil shield. The only ground connection to the foil shield should be one wire from a lug screwed into the foil just behind the chorus board which is soldered to the ground of the output jack on the jack panel. Also you have that gray ribbon cable running over to something on the 366B board which looks like another non-factory circuit board wrapped in some sort of white foam. Is it screwed down? Can you lift it away from other components to see if the noise changes?

Don B.