Vintage Simmons Drums (UK) Users Group

hello out there!

I have 5 SDS-1 drum units and none work properly. I've managed to get some sounds to play on 2 of them but they appear to work differently. The others are more or less dead.

I believe I can troubleshoot them if I have a schematic of the unit. I have a scope, DVM and tools and am pretty good with a soldering iron. Maybe a schematic can be added to the Manuals section in Files... It would sure help me out and probably some others!

Best Regards

Lou

I only have a partial schematic that came bundled with a Simmons SDSV service manual I downloaded which has the V/2 generator and 6V DC input, the decay control based on the 4538 which I haven't found out what kind of chip that is, half of the VCO digital clock, the entire envelope generator circuit complete with pickup and sequencer input jack, and R54 (220 ohms) from the V+ pin on the ZN429 DAC. I actually wanted to see the whole schematic up close, too, and not just the photos shown on eBay.