In my youth, as a Technical Author with Cossor Electronics Ltd, I wrote the maintenance manual for the SSR 1600 Transponder – which I once saw the control unit for on the flight deck of a Comet ( I think ) when I was allowed to have a look by a kind stewardess and captain. That was as close as I got to seeing it used ‘for real’.
Although I was pleased with my work on the manual, and particularly the electronics diagrams, I never had the opportunity to hear from any of the technicians who would have actually used the manual. I think I still have a copy somewhere, but as a longshot, I wondered if a post here might stimulate someone’s memory to let me know what they thought of my efforts. I know I’m talking about 50 years ago, but the Internet can produce some surprising results – but I won’t hold my breath! 
My maintenance company kept telling me in some remote manual some manufacturer wrote such and such so this must all be true. On the other hand a friend works for Airbus, she admits knowing nothing about planes but writes maintenance manuals as a full time job. So I think such manuals should be read but one should keep in mind how they are sometimes produced and also apply some common sense.
Not quite sure what point you are making Sebastian, but I was a qualified electronics engineer writing about electronics equipment to help maintenance engineers understand how the unit functioned so that they could repair it in the case of a fault. The information I provided was meticulously checked by the electronic engineers who designed the transponder, so one could be sure it was accurate.
My post was to try to discover whether the way the information was presented was helpful to maintenance staff – as I said before, particularly with regard to the circuit diagrams which I designed to provide functional clarity rather than just to show the contents of each of the circuit boards. If you had ever looked at old car manuals, you would have seen that their circuit diagrams had lots of straight lines – with loads of ‘dog legs’ – representing the wires joining the sidelights, headlamps, taillights, etc., which were positioned on the diagram relative to their positions in the vehicle. My diagrams were the very opposite of this approach, and were quite novel in those days.
I’m sorry I interpreted the comment you saw the device only once as a wish you had more chance to play with the actual device. Regarding the split between the circuit diagram and the location chart you certainly precedented the current manuals. For example the Piper wiring diagram for our plane focuses entirely on the circuit design. Then there is an entirely different chart which specifies where the actual components are located in the plane.
