der Mouse <mouse(a)rodents.montreal.qc.ca> wrote: The big cavity clearly visible from the rear with the covers off is for the duplexer. The socket in the corner of this cavity right next to the formatter/PSU area is where the duplexer connects, that socket is wired to the DC controller and is very handy for checking voltages. The other socket is on the front directly above the upper tray cavity, that's for the envelope feeder. It is wired to the Paper Input PCA. The service manual contains a one page main wiring diagram. No schematics for individual boards, but at least all inter-board connections are shown with pinouts. MS