A blog about my music, my studio and my DIY projects.
18 April 2011
Korg Poly 800 Repair
As you might have noticed I'm currently selling some of my synthesizers. I had some synths where I just couldn't find a nice spot for anymore and after the Musik Messe I really want to buy the Roland Jupiter 80 and Korg Kronos. So I need even more room now and money. One of the synths I wanted to sell was the Korg Poly 800 that I hardly ever use anymore. But when I tested it some of the knobs on the front panel didn't work that well. So this morning I decided to open it up and investigate what was wrong with it.
I actually expected that some of the switches would be the problem so I started by disconnecting all the wiring from the PCB that holds the knobs and took my multimeter to test all the individual switches. But after doing that they all seemed to work. Then I started to see how the knobs are interfaced and I saw quite quickly that they were arranged in a scan matrix with some diodes on the PCB. So after that I measured all the individual diodes and they turned out OK as well.
So then I started to look on the main PCB where the scan lines were going. And I decided to go and see what happened there with the oscilloscope. So I rewired everything back and starting pressing some knobs. And to my surprise all the knobs worked again. So probably there were just some loose connections on the inter PCB wiring. That was the easiest fix ever I think :) Well at least now you know what a Poly 800 looks like on the inside.
And here it is on the outside. As you can see it is a reversed keys version. At the time I thought it was cool, but now all I can think is that it doesn't fit my other synths :) And since I have enough analog poly synths now I have no need for it any longer. And in the mean time I also have a buyer for it already so it will leave my studio soon. In the mean time I also sold my Alesis Andromeda A6, Roland RS-09 and Roland SH-09. And more is going soon, as said before to make room for nicer new machines. If you like a list of what else I'm selling just let me know, but I have to warn you up front: I don't ship anything so local pickup in The Netherlands only.
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