Archive of the former Yahoo!Groups mailing list: Vintage Simmons Drums (UK) Users Group

That Schematic is very good. It was created by reverse engineering the SDS9 so took a lot of effort. His name is Thierry Eppherre. He is a list member.
I would suggest that you get permission just as a point of goodwill. The last thing needed would be for it to turn up on some pay for manuals site.
The SDS9 is quite complex compared to most brains as the CPU does quite a lot of work and it was the first full midi brain. They all tend to have various issues over time but they are fixable if you have access to some reasonable test equipment and you have a fair knowledge of electronics. I have repaired quite a few over the years. As to what is causing your issues I'd need a fairly detailed description of whats happening to at least head you in the right direction. Is the sound good from the tom individual outs? Is it bad only from the combined outs. Can you vary the volume of each tom? This is the kind of info needed.