HELP! My MS20 is going crazy

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Joined: Sun Feb 17, 2008 9:51 pm

HELP! My MS20 is going crazy

Post by magnus » Sun Feb 17, 2008 10:07 pm

I'm having problems with my Korg MS20. I'm hoping they are easily remedied, as I really don't have the cash to spend £200+ to have it repaired.

The main problem is with VCO1. When I play it from the keyboard it sounds awful - every note fluctuates in pitch. This doesn't seem to happen when I control it through the frequency input.
Also, the octave select knob shifts the pitch by about 11 semitones rather than a ful octave. The keyboard did take it up by about 13 semitones C-C, but I had a tentative fiddle with the trimmers through the front panel, and this seemed to remedy the problem, without improving the octave knob's response.
Of slightly less concern is the fact that a few keys play flat intermittently, whichever VCO is used.
Does this sound serious? Fixable? I remember hearing that there is a nylon connecter somewhere inside that can eventually break and start destroying components, but I don't know what the symptoms are.
Any help would be greatly appreciated.

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Post by Maschinengeist » Mon Feb 18, 2008 7:06 am

If the frequency input control correctly the VCO1, we can assume then that maybe the keyboard CV need to be adjusted. You'll need a digital multimeter. Follow the instruction on the page 10 of the service manual (available online. Use Google)

Octave select knob: should a 100K. Verify it for accuracy with a multimeter. Could be a problem with a transistor. But I'd go with the pot first.

While at it, perform the adjustments outlined in the service manual. Your MS-20 will love you more.

Hope that helps
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Post by magnus » Mon Feb 18, 2008 8:08 pm

Thanks. I'll give it a go

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