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Repair Korg MS20 Vintage Analog Synthesizer Reparatur

Repair Korg MS20 Vintage Analog Synthesizer Reparatur

My customer wanted me to do a full restoration on this Korg MS20 Vintage Analog Synthesizer. It also had one issue with EG2 (second envelope generator). It was like the hold potentiometer was always in full postion, like a short.
 
Repair Korg MS20 Vintage Analog Synthesizer Reparatur
That was caused by a defective ic23, a 4069, which I replaced. Also the electrolytic capacitor was bad. I re-capped the whole MS20, because most of them showed signs of leakage. Like in this picture.You can clearly see the dark spot around the negative hole of the C13 capacitor.
Repair Korg MS20 Vintage Analog Synthesizer Reparatur
Here you can see some corrosion damage under the green solder mask.
Repair Korg MS20 Vintage Analog Synthesizer Reparatur
I also cleaned all potentiometer, rotary, switches and the jacks. Here`s an example of such dark corrosion.
Repair Korg MS20 Vintage Analog Synthesizer Reparatur
And right after cleaning…Now the MS20 works very well and very stable.

Caution


There are lethal voltage exposed in electronic devices. Unless you know what you are doing, don’t try this. If you following along, you doing so at your own risk.
I’m documenting repairs for my reference and yours. I do synth restorations and repair with a specialty in vintage synthesizers, drum computer and other vintage gear, based in Düsseldorf, GER. Get in touch about your synth situation!