Circuit Overview:
I'd been misinformed when I wrote this page years ago thinking this was like ARP pro-soloist; another ROM chip array controlling aspects of analog filters and so on to create the settings needed for the preset button which controls the address bus of the ROMS. In reality diagram shows a resistor matrix; a more straightforward approach perhaps. One reason I put off getting into this is, there are two very different schematics at least and another with some differences. But the machines use a single vco through a voltage controlled bandpass filter which center frequency and bandwidth trimmers can preset and the emphasis panel control can affect, followed by a lowpass filter. Which in one version uses two OTA's and earlier ones a 3 rung transistor ladder with SG3821 arrays. The 'color' control affects the amount of envelope that modulates BOTH filters while the 'contour' control varies the baseline of the same modulation source. ie. look in the eg. section to find the contour.
Service Tips:
First of all figure out which diagram yours needs, comparing board diagrams in the various service manual renditions. If you have the regular moog version it's probably going to fit the diagram listed above. I have two other Diagrams I think here if you need to send a photo of your board to see if mine is a better fit. Key contacts were the issue on the Thomas version I documented in the Video.
Parts:
Have most of the parts here for them electronically.
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