I have scanned the operating and the service manual for the Sinclair DM-235 multimeter. I also included a schematic of the resistor network, as obtained by reverse-engineering, on the last page of the operating manual. Both are available at the links below. Hope this helps someone!
Sinclair DM235 Operating Manual (including resistor network schematic): http://home.comcast.net/~medasaro/DM235_OM.pdf
Sinclair DM235 Service Manual: http://home.comcast.net/~medasaro/DM235_SM.pdf