Yamaha CS-50 Analog Synthesizer 4 voice

via this auction

"The Yamaha CS-50 has 4 VCO's and 4 VCF's. It has 4 note polyphony. You can play 4 notes at a time.

The keys work perfectly. The PW and PWM potentiometers are damaged. But the Pulse and Saw wave VCO's still work fine. This CS-50 works well enough to play.

The filter ENV works. The VCA ENV works, except for the DECAY pot is not 100% functional.

The "Tone Selector" section : String 1&2, Brass 1&2, Flute, Electric Piano, Clavichord, Harpsichord, Guitar1&2, Funky1&2&3, & Panel: All of these work fine.

The "Transposition" section ": 1&2 OCT DOWN, Normal, 1 OCT UP ...works fine

The "touch response" controls: "Sub VCO, Oscillator VCF, Brilliance and Level" need servicing.

The "Foot Controller" jack has a problem. I tried plugging in an Alesis Foot Controller, and the CS-50 blew a fuse. (The "-15V" fuse)

The "External IN" jack works, and it causes VCO FM, VCF FM, or AM. The sound at the "External IN" jack is also heard at the Main OUT jack.

All of the other controls work fine.

I added an RC4558 op-amp to boost the output sound.

The sound is very good. This synth is fun to play. The VCO, VCF and VCA are all 100% analog. No DCO's or anything like that.

There are a few scratches on the front panel.

The signal to noise ratio is about -50dB.

The CS-50 is a "Performance Synth." It is meant to be played by hand, like a piano. There is no onboard sequencer. There is no Midi IN or OUT. There is no GATE CV INPUT. There are no CV inputs at all."