Data General NOVA 4/C help

I picked up the NOVA 4 last Thursday. I had help carrying all the stuff (disassembled) downstairs from the attic. At home I had to unload the van single-handed. Went well, although I felt my back that evening ... Today, I cleaned the rack, as all boxes were still on the floor. There was little dust, the machine was well taken care of. After the cleaning I mounted the hard disk drive on the slides. The hard drive is a model 6101-S2 (12.5 MB fixed disk). On the top plate of the hard disk is an 8" Qume floppy disk drive mounted. The hard disk and the floppy disk form one unit, never seen this construction before! The colored twisted-pair flatcable from the floppy drive goes to the hard disk and another colored twisted-pair flat cable goes to the NOVA 4/C computer, connecting on a paddle board using an edge connector. See my website: www.pdp-11.nl/dg/nova4/nova4.html After everything was connected I applied mains. The fans start to run, so far so good. Then I switch on the NOVA and then the hard disk unit. The POWER LED on the NOVA and on the hard disk is lit. I can hear the hard disk "hum", and when the humming sound stops after a few seconds the READY LED is lit. However, when I press RESET on the NOVA and then PR.LOAD, the READY LED on the disk flashes momentarily (brief), but nothing further happens. On the disk drive are (behind the panel) two small switches. One has the text "NORM" and "PROT", the other has several texts (forgotten), but with that switch you can set the hard disk as device 0 and the floppy drive device 1, or the hard disk as device 1 and the floppy disk as device 0. Basically you can set the boot device, as the machine starts from device 0. I have this from the accompanying documentation. When I put that switch in the other position and press RESET and then PR.LOAD on the NOVA, the floppy disk LED is lit for a few seconds, but I do not hear a head load ("clunk"), nor head stepping sounds. Of course, the floppy drive is loaded with a floppy disk. The label on the floppy says "opstart" (Dutch for start up). As the floppy disk access LED turn on, I guess that I can say that the NOVA itself is OK. As far as I know, I have the BERG connector put back on the pins where it was before I did the disassembly. That cable connects to the terminal. The question might be whether it was on the correct pins for starters. I do not get any character(s) on the Dasher D200 terminal that came with the system. For that reason, I assume that the terminal settings match the settings for the NOVA. One more remark. On the hard disk is a red label glued. The text on it says "remove 2 shipping brackets before operating unit unlock pivot arm (see over)". On the rear side of the label is a drawing that shows the "front left corner". At the side is a screw (???) to lock/unlock the head(s). However, I just don't understand the drawing and cannot localize that screw. I mailed the previous owner whether he remembers something ... Anybody has info on the 6101-S2 disk drive? A drawing of those shipping rackets, and more info about head locks? Thanks, - Henk