Technics Digital Piano SERVICE MANUAL or info needed--my Digital Ensemble model is SX-PR50V, but keyboard encoders (my interest) are probably all the same that era. Two notes dead, all else maddeningly perfect. I wish I knew which diodes to check before disassembling the sensor board, hate to cause alignment problems or something, do no harm and all that. I could even break out scopes etc if I got seriously stupid, and had a schematic hopefully. Any tips? Chassis disassembled on dining room table....