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My customer wanted me to do a full restoration on his 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.
That was caused by a defective ic23, a 4069, which I replaced. Also some electrolytic capacitors were bad. I re-capped the whole MS20. 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.
Here you can see some corrosion damage under the green solder mask.
I also cleaned all potentiometer, rotary, switches and the jacks. Here`s an example of such dark corrosion.
And right after cleaning…Now the MS20 works very well and very stable.
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!