105 – TX81Z Repair

This morning, after making myself some strong coffee, I opened up my Yamaha TX81Z and changed 3 of the capacitors on the power supply board. These help smooth the output of the power supply so that it gives a stable voltage to the main circuit board in the synthesizer. You might have read about the power issue I was having in an earlier post. I’m almost 100% certain that it’s been fixed by this repair as it hasn’t been shutting off anymore. It was really rewarding get it working again and I learned a lot from doing this. I also figure that discussing how I got to this point would possibly helpful for somebody else, so this post will explain that.
 
In troubleshooting the problem, I wasn’t sure where to begin, so I began by looking for some help. I found a yahoo group called Yamaha Black Boxes, which is dedicated mostly to FM Synths that Yamaha made in the 1980’s. I posted about my TX81Z and described the issue that it was having. Several people responded with useful and helpful information, including how to test the power supply and circuit board (be very careful!). I ended up getting a digital multimeter, which makes a huge difference when testing circuits. A guy named Alan suggested changing 3 of the capacitors on the power supply board, saying that they usually go bad due to what they are made up of (foil and paste, basically).
 
It took a long time to dissassemble the synth and get the power supply board out of the casing, but the actual process of removing the capacitors with the soldering iron wasn’t too hard. Putting the capacitors in wasn’t hard either. Here is a great comic that’s fun to read and explains soldering really well. It’s called Soldering Is Easy. One thing that’s REALLY important with capacitors is that they go in properly with the negative & positive leads in the right places, which is indicated on the part and the board. Since I couldn’t get one of the capacitors at Radio Shack, I ordered them from Jameco Electronics and they came pretty quickly.
 
In this process, I also found some great videos from Make Magazine by Collin Cunningham. He goes over multimeters, schematics, tools, and more.
 
This was a great experience and confidence builder. It made me think that it might even be fun to buy a broken synth one day and fix it. My next project will probably be fixing some of the electronics I have that don’t work (two tape machines and an old record player). I know this is probably the longest post I’ve written for Noise Cycle, but I hope that somebody finds it interesting if they are trying to get into repairing/building electronics as well.
 
(The artwork for this post was created with Decim8 for iPhone and originally was a picture of the TX81Z LCD panel)
 

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