One of my growing hobbies is synth repair. Buying broken devices and trying to fix them. In the early days, it was because I wanted to play these devices. I was building my studio and I needed and wanted these devices to work right now. Now that my studio is filled, that urgency kind of drops off and things can sit around for as long as they need to before they get fixed, if they ever get fixed.
This Kurzweil keyboard I purchased over a year ago has been waiting for a donor board for a year, and when I finally got one, it had problems too. So now I have two unusable boards. But, due to the lack of urgency to fix them, I’m able to take the time as a learning experience and allow myself to make mistakes and try to learn as I go. So while the end result might be that neither of them work, I’m learning things that lead up to the final diagnosis of unfixable.
When I started, the one board sad it had bad ram and the other said it had a bad CPU. These are not solvable problems (for me). However, there are other problems that I can try to solve in the interim. For example, both boards have bad backlights in their display. I’ve discovered they use CCFL bulbs instead of EL sheets. This is new to me, so I’ve learned about the parts and repair of those.
After swapping the bulb, there was no real change. I could have given up right there, but based on past experience, a symptom like that suggests a power problem. The vast majority of electronics problems are power-related. The extent of my knowledge on that topic is changing capacitors. I had recently purchased a capacitor tester to support this limit of my knowledge and my tests showed that yes, a cap was bad near the backlight assembly as well as on the power supply section. Parts ordered. Days go by.
After replacing the caps, the backlight was better, but still not perfect. So I was on the right track, just needed more digging. Something most techs start with, but isn’t really in my troubleshooting list is using a multimeter to test voltages. I usually bypass this step because I don’t really what is good or bad. I test the voltage at the cap I just changed. It’s like 4.8 volts. I have heard and read that most devices either use 12 or 5 volts internally, so it looks to me that there’s an underpower situation. I probe farther back and its the same low voltage all the way back to the main power section. I test some of the capacitors in that area and find one that reads bad.
One of the things I’ve started doing is buying excess of any part I need, assuming that if I needed it once, I’ll probably need it again. And sure enough, I have a replacement for this cap on hand. When I flip the board over to unsolder it, I see the soldering points for the voltage regulator right beside it are darkened. The pieces are starting to fit together. Capacitors fail from exposure to excessive heat. Voltage regulator nearby getting hot enough to discolor the circuit board. Voltages are not to spec. I pull the voltage regulator and order a replacement (and spares, of course).
So all this time, I have all these parts and tools scattered all over my kitchen table. It’s a disgusting mess, but I live alone, so who cares? If I had another spare room, I could have a workshop, but all my rooms already have purposes. And again, this may be all for naught. Maybe I do get the backlight working fully and it doesn’t matter because the mainboard is shot. But the value in learning has been gained. I did some troubleshooting steps I hadn’t done before and identified issues that I might have made me give up before.
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