rock soderstrom said:
here a link to some of their famous "Baumappen" ("Build instructions")
http://sites.prenninger.com/elektronik/bausaetze/rim/rimbaumappen
Fantastic...
Looking at rock's RIM build instructions (which I wish I could read in English they look awesome) I notice that there are some that refer to the ELA-1004 system in the index. These might be a good place to start (if you speak german, or even if you don't and can match up the schematics).
I don't but here is what I picked up using google translate and my nose. The thing looks so well documented and organized that it is easy to follow even with my minuscule German (I had a german stepmother, briefly, 40 odd years ago, who tried to teach me):
in the index ...
There is an ELA - 1004B system
There is an ELA - 1004E system
and
There is an ELA mini system is dated 1971/72
The mini system it seems was a block system, which included individual blocks one block of which was the VV subsystem (maybe pictured, although yours seem to be part of the 1004 system).
The VV blocks maybe were part of the Preamplifier blocks it seems.
Here is the index google translated and guessed
block system of individual blocks
VV preamplifier
KL Klangreglverstarker (Universal line level input?)
SV Linear sum and output amplifier
RKL equalizers? -
EM Mithorverstarker (output amp?)
VU AM
NT 1 power supply module
NT 2 Power Supply Board
WS selector
There are more than one that document the ELA system, even the ELA1004 system.
Find someone who speaks german or even without that, you may be able to use the schematics on the ELA modules to work backwards to the voltages and bus structure on the Tuchel connectors.
Especially if other modules have RIM stuff in them.
How much of this stuff do you have anyway?