I was kind of excited to work on this because it is the close relative of my own and favorite polysynth, the Kawai SX-240. The repair job started out smoothly and then descended into hell. The owner of this synth had just received it in the mail after buying it online, ostensibly fully functioning, but apparently it arrived seriously banged up with various pieces broken off inside (including the transformer) and not making any sound. After only a couple hours I had it playing again and thought that all I had left was to put the wood pieces back together (should only take an hour, right?)
The next day I began trying to reassemble it, but quickly realized I had underestimated how long it would take. All of the wooden body pieces were originally just held together with staples which had pretty much all torn out. It’s just a bad design, and really didn’t stand much of a chance. I finally resecured everything, requiring the addition of a lot of wood glue and various wood screws and bolts. Worse yet though, I started encountering intermittent electronic faults– DCO clock outputs not reaching the wave generators, voices dropping out, patch memory randomly corrupting.
This took me a long time to figure out, but I eventually found no fewer than 11 tiny (literally invisible except when the board was being flexed) hairline cracks scattered around the analog PCB that I had to repair. The hardest part was finding the first one. Because it is a problem I see so rarely, I didn’t think to expect it– once I understood that I should be looking for those invisible discontinuities, things got a little easier. Seriously though, this is the kind of task that can make me feel like I’m losing my mind. I’m worried there might be more that haven’t started causing problems yet… what a nightmare.
Work Done: replaced leaky NiCad battery and cleaned corroded areas from battery leakage. identified and repaired various torn-off wires. Replaced power supply capacitors. Removed, stripped and reattached soldered-in ends of 4 ribbon cables that had had many of their wires broken off. Reinstalled transformer in a different spot where wood wasn’t damaged– there is no room to add a reinforcing wood piece under it as I had originally planned, there’s not enough clearance between the transformer and the panel! You already read about the other stuff I did. Loaded factory patches. For some reason, one of the best ones is called “MOTELS.”
Important Note: when you replace a rechargeable NiCad battery with a lithium or other non-rechargable one, you have to put a reverse-biased diode before the + end of the battery to keep the synth from “trying” to recharge it and ruining it. I always just use 1N4148.