Yamaha CS-40M -1979    Weight = ? Lbs. Number mfg.= ? MRP=$2195

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 probably can be done in any dual vco CS synth though the 40M may require a lot of modifications
General Info Links: Vintage Synth Explorer or Travelogue review

Circuit Overview:
     A subtractive analog synth similar in many ways to other CS series, but this one has a duophonic capability. Not sure which method they used. Similar to CS20M in memory design I'm sure.

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. SEE CS20M for more tips since I've never worked on a CS40M and the 20M is very similar. Also fuse resistors may blow in the insulating jackets in PS if fault occurs.

I had a most peculiar manifestation shown in a video I did on CS5. The cutoff control would just cease to impact a highly filtered sound at the Ab second from top and below or like that. It would change a note during warmup. Turned out the VCF chip was the issue!

Slider caps and Knobs- I have a decent selection of rotary knobs The sliders are identical to those used in Moog Opus 3 etc. I have some reproductions from chipforbrains. Not cheap since they're out of production again i think. I try to keep some crude reproduction slider caps in at 6.00 each.(Contact Sound Doctorin')

Semiconductor and Parts:

See Semiconductor page. I believe I should have any electronic part or keys for these save exact transformer, etc. Ask if you have need.
Contact Sound Doctorin'