A simple subtractive analog synth similar in many ways to other CS series.
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.
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!
Also I figured from schematic and the manual deciphering Japanese as best I could, that you first tune VR4 and fine tune vr3 to get the high pitch C in 2' setting to the frequency shown in the chart..8.9Khz or so using frequency counter. Then the lower C's with VR2 and center tune with VR1 around til it's all right. It's all interactive some of course. Clean the trimmers first.
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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