Yamaha CS-20M -1979    Weight = 37 Lbs. Number mfg.= ? MRP=$1595


User Manual: Yamaha
Reset Proceedures: N/A
Operating System code: N/A
MIDI or other control protocol: N/A
Software related Links: N/A
Patches or knob settings:
Circuit Overview: below
Scematics/Service Manual: fdiskc archive or Manual Manor
Common Service Issues/Tips: below
Parts Sources: Keys knobs semiconductors misc
Uncommon chips/modules used:M51620P/IG00150 lfo chip, M51621L/IG00151 VCA's, IG00153 VCO, IG00156 VCF, IG00158 WSC, IG00159 EG/VCA, uA796HC gain cell, BA634 divider, BA617 OTA, YM615 key assigner, YM616 cpu, YM617 mux/demux, lots of TC series chips.
Modifications:Eric's CS-15dx modwhich I believe is adaptable to all dual vco cs synths.
General Info Links: Vintage Synth Explorer

Circuit Overview:
     A subtractive analog synth similar in many ways to other CS series. Sine wave feed past filter to thicken up things. All knobs and 8 memory locations with typical knob scanning by CPU through analog switching.

Service Tips:
     Typical problems in CS series are power supply over voltages which blow tantalum capacitors and they short, or the caps just fail over the years. During this various chips may be taken out. I've seen LFO chip, VCA's and dac comparator fail so they might be most susceptable. In recent one the YM617 MUX chip failed out of the blue after running solidly for quite a while. Fortunately Yamaha still had some!

Parts:
I believe I should have any electronic part or keys for these save exact transformer, etc. Ask if you have need.
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