The MS-20 is a monophonic patchable analogue subtractive synthesizer, produced by Korg in 1978.
ms-20_vcofm.png- schematic of the VCO frequency modulation circuitry, hopefully clearer than the original
Does anyone have better scans of the service manual than the ones on Ben Ward's site ?
|H1||4 × brown|
|H2||7 × red|
|H3||8 × orange|
|H4||3 × yellow|
|H5||3 × green|
|H6||3 × blue|
|H7||brown black orange|
See also Kevin Lightner's photos.
The connectors were made by JST. Closest match in their current offer seems to be the NH series (pitch 2.50 mm). Digi-key reference a bunch of JST NH parts but only stock the female contacts (SHF-001T-0.8BS) and 3-position housings (H3P-SHF-AA). In a pinch, 0.1" AMP MTA and Molex Mini-KK connectors seem to mate with the JST connectors (but do not lock as the keying is different).
Factory 2012-09-18), the North American models had a single 120 V
primary while the rest of the world had a three-tap primary : brown
wire for 100 V, orange wire for 220 V and yellow wire for
Mine is a 220 V model and the transformer (stamped KA-221) matches
that description : four wires on the primary, mains between black
Secondary is centre-tapped, most probably 18-0-18 V (see synth-diy thread). Rated power unknown.
Over the years, my MS-20 developed a wavering.
The cure was to replace IC5 (CA3140).
See the thread on the
part 4 (two messages missing),
files/lpfres-vs-inpamp/- demonstration of how LPF resonance varies with input amplitude
ms20-dualres.ogg- illustration of dual resonance made possible by having two VCFs (and extremely dodgy playing)
ms20-dualres.txt- patch for the above
ms20-tsr12-loop.ogg- many layers of MS-20 looped with a Digitech TSR-12
ms20boing.mp3- boing sound
ms20shot.mp3- shot sound
ms20zip1.mp3- zipper sound
ms20zip2.mp3- zipper sound
telegraphiste-3.1.mp3- note how the exponentially controlled VCF fails to track the linearly controlled VCO
Unless otherwise noted, all recordings are of my MS-20, which has the earlier KORG35-based filters, not the later LM13600-based ones.
This is http://www.teaser.fr/~amajorel/ms20/, last modified 2014-03-30.