Circuit Overview:
An 8 bit ROM based sample machine with wavetable joystick control and a cool AM routing. All cheap digital design. Amazing machine for it's day in terms of features/price. Came in Rack and module/table top version as well as 61 key keyboard. The K1-II just adds fx and some kind of drum set organizer as I recall.
Service Tips:
I haven't really seen any issues with these but from looking over one of my modules I imaging solder problems have happened. Even fixing that I still have a pop when envelopes decay all the way. My other one doesn't seem to do it. Annoying!
Parts:
Most of the parts are going to be pretty hard to find I'd think on these and they're probably available too cheap to worry much about it. :-)