Yamaha CS-50 Synthesizer w/ 6-Voices & Aftertouch Mod

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via this auction

pics of the inside below.

"I bought a CS-50 years ago and modified it with a couple of extra cards to be a 6-voice. It is serial number 1031 which is the earliest unit I know of. The rails were actually drilled for six voice cards from the factory; I expect they intended the CS-50 to be a 6-voice and later backed off to four voices. The two additional voice make it much more musically useful IMO.

The new voice cards are original CS cards that were plumbed into the SH and KAS boards with the required modifications on those boards to make it happen. The wire looms were made by hand using Yamaha wiring and all the correct color-codes (of course) which match the coding in the CS-60. It's a very professional job using wax-coated lacing for the harnesses.

The voice boards have been modified to include LEDs which illuminate when the card is activated for ease of maintenance. All circuit boards have been fully recapped. The power supply has been fully-reworked with a new power cord, all-new capacitors, rectifiers, opamps and all power transistors on both the circuit board and the heat sink.

It has also been modified to have Sustain pedal function like the CS-60 and CS-80. I did not add an On/Off switch on the panel as on the later units, rather all the switching is done internally when a Yamaha sustain pedal (or other NC pedal) is plugged into the added socket on the back panel.

It includes the lid, but there are no legs. The metal box that contains the power cord when it is stuffed up inside the synth is missing. There are some scratches on the left modulation panel and right power switch panel, but the main panel is in pretty good shape.

Another modification I did was to re-route the aftertouch volume Level paddle to instead control the LFO Speed. I find it much more expressive that way, but I can easily put this back to normal operation if a buyer would like to have that modification removed. The unit has been completely calibrated and is ready to go."