Circuit Overview:
Another mostly preset based subtractive analog synth in the fashion of ARP pro-soloist, having preset voicings that can be globally manipulated by sliders for vcf and mods, with only one preset available at a time. In fact even has aftertouch. However it's a magnetic sensor that is way too sensetive for me actually. I prefer the ARP with it's sensor strip that has to be pressed fairly hard. You get used to it though somewhat. It also differs greatly from the ARP in how the presets were implemented. ARP used ROM chips programmed to put out high and low lines in accordance with the needs of the facilities they are tied to (eg. some are tied to filter elements in op amp feed back loops so as to activate or deactivate the analog function basically. ). Roland however used discrete logic basically it appears. Much higher device count but easier to fix if something goes wrong of course :-).
Service Tips:
Watch for dirty contacts, including the power switch which can kill one or both sides of the power supply (it's a dual pole switch which gets power to the two halves of the transformer that create the independent voltage rails to run this thing. This brought mine up and running with a simple cleaning!) LATER I began to see issues with the tuning going crazy. I finally figured out it was related to the Portamento amount. The electrolytic capacitor near the slider for portamento is difficult to get to without pulling everything apart BUT YOU CAN just desolder it and knock it out of there. Then install another cap underneath the board instead! Much much easier.
I stock remanufactured knobs for these machines! Slider or rotating small knobs 3.75 each large $5 each
Parts:
I have a variety of parts that might help you on these as it appears Roland used many of the same parts those years. And also there are some discrete components that I usually stock.
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