Yamaha CS-15D -1979    Weight = Lbs. Number mfg.= ? MRP=$1095

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:
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, IG00159 EG/VCA, YM24800 key assigner
Modifications:Eric's CS-15dx modwhich I believe can be adapted to all CS dual vco synths.
General Info Links: Below

General Information:
     These machines use a lot of the same circuitry as CS-15 and other synths of the series. So a lot of troubleshooting can be done using those service manuals for filters and so on. The CS-15D however only gives knobs for the settings on the second VCO. It also offers presets if you don't choose to use those knobs but you can always tweak the global settings which are typical of preset monosynths plus a few extras. But the first VCO is entirely presets and there is a pan slider between the two VCO's channels. It's a great sounding mono and...apparently pretty rare. I've only seen a few on ebay and some nice person decided they wanted to give it to me on a buy it now for 200 with flight case! Thus began my appreciation for the beauty of the Yahama filter design. The presets are quite cool actually. They have an ethereal character that isn't strange like the Pro-soloist but isn't cheesy consumer oriented either! I'd like to know how many they sold.

Circuit Overview:
     A simple subtractive analog synth similar in many ways to other CS series.

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. If PS fault check fuse resistors in insulating jackets.

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!

The knobs for these are a black knob w/white pointer tht I think I have similar ones to if not same. The sliders I don't think I have the same thing for these. Several failures of YM24800 keyer chip have been reported over the years and Mail Dean at Five Star to get on his list because he has successfully created a retro board to replace these impossible to find chips! I believe I should have any electronic part (except assigner) or keys for these save exact transformer, etc. Ask if you have need.
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