I got a supergun like this one but was not correctly working.
So in the past months I do some wiring works on it and now it's working great with a 3 buttons megadrive pad.
Me too have had sync problems in my lcd with some games (even with neogeo boards).
hi,no earth terminal used on the switch mode?i would use the earth for sure the casing of the switch mode is metal,your supergun would be more electrically safe using the earth terminal,all kettle leads use earth.