I use a Wallner System 500 Modular system in my darkroom. It was purchased impulsively a few years ago and has served me quite well. I have found little information or support sources on this gear and have started a Google group as a place to accumulate information and share experiences. The group is at:
http://groups.google.com/group/wallner?hl=en
I've uploaded the material that I have as a start. It's a public group and perhaps over time, people will find it and add to the information. I'm using the System 500 Labex/Wallner...picture attached.
The group is closed, But I was lucky to download manuals in 2010 from it.
Meanwhile I collected whole lot of stuff related to Wallner, but still have no info on CA2004DVM. I also PM'd you, if possible please reply.
Wallner's business was taken over in 1988 by FEM Kunze, and they still make darkroom meters. You may be able to obtain information from them.
http://www.fem-kunze.com/
I made a call to them and got following info - web site is closed and they won't open it any time soon. And lady said they plan to shut the phone in the end of thi year as well. Maybe I misunderstood, but it was said like that.
Also they don't seem to be happy answering questions about old wallner equipment. So Wallner owners - Brace yourself!
I got a scan from magazine from 1986 with description of mods for MC505.
I'll put them here later and also try to translate it from German. It describes memory mod and footswitch mod for timer operations.