[REWARD] Request for documentation - update

Actually, I do have a photcopier... It'smodern, and yesm, the cotnrol electroncis is based on one ASCI, presuably a microcontroller at least in part. But it;'s old-fashioned in that it's an optical thing, the ligt frelected off the original is focussed on the photoconductiove drum, there is no CCD or anything like that. And I feel I could rebuild the complete control system if I ahd to (a lot easier than driving a random CCD anyhow).

It was a manual electrostatic plain paper photocopier. I think Xerox produced them in limited numbers to trial the concept, before making an automatic machine, hence the interest from the Science Museum. The thing to be copied was placed behind a vertical glass plate, lit by a couple of 200W lamps, opposite which was a huge bellows camera. The camera could be moved along a graduated slide, to give an image between 50% and 200% of the original. After setting the copy ratio, you put a ground glass screen into the back of the camera, to set the focus. You then put a coated flat plate, mounted in a wooden frame, into an electrostatic charging chamber, ran the charging cycle and slid a lightproof shield over the coated side, before removing the plate from the chamber. The plate then replaced the ground glass screen and you withdrew the lightproof shield for the required exposure time, which IIRC was quite long. Once exposure was over, the lightproof shield went back in place and the coated plate went on top of another chamber, which contained a mixture of beads and toner powder. The shield came off again and the whole chamber was turned upside down and rocked to and fro on a central pivot, to run the beads and toner over the exposed plate. The toner stuck to the areas that had not been exposed to light in the camera (i.e. the black bits on the image of the original). Once that was done, the plate could be removed from the toner chamber (after turning it the right way up) and a sheet of paper placed, very carefully, over the coated surface. I think there was something to hold it in place. the whole lot now went back into the electrostatic chamber and the charge reversed, so that the toner was drawn onto the paper. ISTR there was a plus and minus control, although I forget which charged the plate and which transferred the toner to the paper. With a bit of luck, you now had a piece of paper covered with black toner powder, which was very delicate and easily smudged. That went into an oven in the apparatus for a few minutes. When it was cooked, you had your photocopy. It took about a quarter of an hour to do a single copy, although multiple copies could be done a bit faster per copy, as you could be preparing another plate while the first was being exposed and be doing the toner for that while the first page was cooking.