Hi, I'd like to introduce myself to the list and see if anyone out there has access to a usable SDS 7 Service manual.
My SDS 7 Saga :
About six months ago I restored an SDS7 which had been sitting on a shelf with a burnt out power supply for many years. It worked flawlessly with five voice cards for a few months when one day I came into the studio and found it had lost it's memory. Turned out that the battery for the digital memory had burst. I replaced it with a standard lithium memory backup battery of the same voltage from Radio Shack. This arrangement worked quite well for several more months, until that battery also burst, this time with enough force to effectively destroy both of the digital boards, (the ones located behind the keypad).
In the course of rebuilding it the first time I got a pretty good sense of the method whereby the parameters are transmitted to the individual voices. There is a complex staircase-like waveform that has all the analog voltage levels strung together, presumably to be de-multiplexed by the "hybrid" module on each voice card.
Now I'm entertaining the notion of embarking upon an effort to resurrect the voices using a more modern digital control section, potentially with midi control and pots or encoders, per parameter (15 of them). The main roadblock at the moment is that I don't have a legible copy of the Service Manual which had the circuit topologies. I do have the pdf scan which is available at
http://www.simmons.synth.net/sds7/Unfortunately that scan is of low enough resolution that the important details in the schematic sections are totally obscured.
If anyone has, and would be willing to share, this information. That would be wonderful. I would of course, in kind, return the fruit of these efforts to the list, should those actually bear any usable reults.
thanks,
Brian