Spare parts could be a worry, and that crossed my mind when I took the keyboard in for repair. I guess the -15V DC regulator is a generic part and so didn't have to be a Technics component, although I didn't ask about that.

KN7000 users may like to know (or may NOT like to know) that when I took the keyboard in and explained the problem, the repairman said that hopefully it will just be the negative 15V DC regulator. Seems to imply it wasn't the first case he'd encountered!