REI <==> Reverse Engineering, Inc.

Old Crow's Synth Shop: Korg Polysix Upgrade & Repair Overview

Welcome to the Polysix synth shop at the Old Crow's Network. Here you will find detailed, fully illustrated information on how to make repairs and upgrades to the now-vintage and classic Korg Polysix programmable 6-voice polyphonic music synthesizer. This machine was designed and built by the Keio Laboratories of Tokyo, Japan in 1980-81, and was available for retail sale in 1981 and 1982 before being replaced by the Korg Poly-61. This author's opinion is that the Poly-61, while having two oscillators per voice, did not have nearly the same degree of programmaing flexibility as the Polysix, and the Poly-61 was therefore an inferior "successor". The Polysix was one of the last machines built prior to the third revelation in modern synthesizer design: the digital synthesizer. (The first was Bob Moog's use of voltage-controlled elements, the second was the incorporation of microcomputers into the hardware to allow for programming, editing, and storage of patches). At the same time the initial digital synthesizers were making their debut in 1982-1983 arrived an innocuous little interface that was to change everything from that time forward: MIDI, the Musical Instrument Digital Interface. No longer were synthesizers isolated from each other. Now they could talk a common protocol between themselves, allowing each machine's keyboard to control the others, take instructions and scores from computer sequencer/patch assigning/composing tools and likewise send the realtime performer's keyboard playing to be recorded and recalled...just to touch the start of the immense list of options that MIDI has opened up over the years.

One of the items that will be present here on the Old Crow's Synth Shop is how to put MIDI into your Polysix. Two approaches will be offered: Richard Wolf's very nice Z80-based processor replacement board that 1) provides a comprehensive MIDI capability and 2) replaces the original Polysix CPUs with a single, much more capable processor to make future upgrades easier. This approach requires moderate circuit-board modifications, but the end result is a very flexible MIDI scheme. Richard has a site detailing his project at his Polysix-M site. The other approach features the second-generation design of my own MPX-61A MIDI-to-Keyboard-Matrix encoder. This method requires almost no modification to the Polysix itself. The original precis on the MPX-61A is available at my MPX-61 site.


NOTE: If you have a Korg Polysix and have never changed out the original backup battery, GET IT DONE NOW!! If you are not sure whether the battery has been replaced, open the unit and do a quick visual check. That battery is nearly 20 years old and long past the end of its expected life. Ni-cad batteries such as the one originally used on the Polysix do not go quietly, either. All too often they begin to leak on their negative terminal and the resulting corrosion in the area of the circuit board where the battery is mounted can cause the machine to fail. ALL Polysix units are now subsceptible to this problem, so have it checked out as soon as possible.

Opening and Inspecting the Polysix

The Complete Polysix Battery Repair Procedure

The Keyboard Cleaning Procedure

Give Your Polysix a Korg PS3100-style Triple Resonant Filter

The The Polysix Service Manual, "Mini" Version

Scott Rider --