Vintage Simmons Drums (UK) Users Group

New member on the list, and obviously I’m here in need of help.

 

The other day a took delivery on a 9 voice SDS7 where seller pointed out it needed a new battery and that one channel was triggering all the time. As it turn out this thing need a lot more help than that.

 

I found sensitivity potentiometer on one channel broken off. Hopefully this is the retrigger issue. Sourcing 16mm pot with long 4mm shaft will prof difficult I think. Anyone in the know where to get one? If not I’ll try to reuse the old 4mm shaft and use shrink tube and glue to a standard 5k Alpha pot with 6mm shaft.

 

Battery I’ll probably copy Jesper’s approach. One question regarding the original battery. Trying to source a new NC-M battery I found that there is something called Lithium-ion NCM. This is a battery that can be charged. To clarify, do SDS7 charge the original battery or is it a Nickel Cadmium?

 

Readable schematic for SDS7 has also proven difficult to find? I’m trying to get a understanding/documentation of the card buss and how and when the main board issue sound parameters to the bus/voices. Is it sending CV or data?

 

The first SDS7 I owned way back when you had to trade your car for a SDS7 kit had a rather nervous fly wheel selector knob build with LED’s and light sensitive resistors. My "new" specimen has a closed dented selector. It looks like its original mounted. I can understand why they changed it. But the speed wheel thing was great fun in use, when it functioned that is.

 

I’ve posted pictures of my disassembled SDS7 at http://snw.lonningdal.no/sds7/

 

I easily get side tracked with new ideas and projects. But my intention for the SDS7 is to modify it when I’ve sorted out some of the quirkiness mine has. I’ll like to have 3.5mm trigger inputs on front panel. Maybe try replacing a couple of the EPROM’s with Flash chips. Or load SRAM from SD card using Arduino. If I can get my head around the bus structure maybe I can have real-time modulation with CV control for some of the parameters?

This is a part number from a post I put up in March 2014.
The Digi Key PN for the pots I will be using is: 987-1572-ND

Not sure if those will work on your model, but it's a start.
The shaft diameter is different, but they worked great.

Rich

Thanks Rich!

As far as I can see 5k Alpha pots from Tayda will also fit. But with wrong shaft length and dimension.

I also got a tip off list to visit Kessler electronic. They do stock 4k7 pots with correct shaft 4x32mm. But sadly only in Log scale. Great for a volume control, but not so much for sensitivity adjustments.

 

I guess for cost reason Simmons used Linear pots in both position. That’s why all the volume controls feels like they’re broken with only a very short useable scale at the end.

 

Of course I could move the Lin volume pot to the trigger position, but then I will eager to modify all my voice cards to have Logarithmic volume pots.

Actually this is a worthy modification if local volume control is needed in ones setup. But doing so it would make sense to use better quality potentiometers than these. Even those 0.5$ Alpha pots at Tayda are smother and better quality than what’s used in the SDS7.