Thread: Korg SQ-64?
Have you tried a different wallwart supply? This sounds like a switching supply issue, because switching supplies tend to spew RF garbage when they're either in the process of failing, are being overtaxed by too much of a current draw, or just have sucky design in general. My bet is on #3, actually...find something with the right plug polarity and voltage but DOUBLE the available amperage. Fact is, there's a whole lotta processing going on in that box, and it might actually be overdrawing even Korg's own OEM wart!
...and even if that's not the issue, that bigger P/S will still be useful somewhere. But that's where I would start.