So, my amateurish trial and error fumblings continue. I post this stuff, not in a narcissistic way, but to contribute to the greater knowledge, since I have found many answers I needed in ground previously plowed by others. If I should stop, tell me.
I have disassembled 2 Model F 122-key terminals today, 1 from 1984 and 1 from 1985. Below are pictures of the circuit board/metal backplate assemblies, which I do not wish to take apart. They are surprisingly different. The 1984 (August) model is the one that looks all green, as if there is a much thicker layer of fiberglass over the printed contacts. It was in much better condition, and the metal back plate is quite shiny.
The 1985 (January), which is much like the 1985 (June) that I re-habbed and have been discussing for the past month, has the coppery-looking contacts.
My question is which of these boards should I use for my next project? I like the idea of the stronger coating over the circuit, since I have seen a Model F board (an XT 83-key) in which the copper looked like it was more than half eroded (or otherwise erased) away.
The 1984 looks very clean and nice otherwise, and unless there is a compelling reason for the actuation to be harder, such as the electrons have to work harder to get through the extra thickness of fiberglass, then I will use this one.
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I am an Industrial Designer, not an Electrical Engineer, so my intuition is not so deep in this realm. All else being equal, I will chose physical strength, but not at the expense of free flow of energy. Many of you must understand the subtleties and/or minutiae of this process better than I, but you know, miniscule differences matter to me.
Lastly, the rubber mats were in "bad" condition. I was spoiled because the June 1985 in my previous project had a very nice mat, not only was the rubbery surface quite nice, but the foam side was also mostly intact, shedding some 10%-20% but hanging together pretty well.
The mat of the 1985 was terrible, the foam was completely gone, transformed into a very ugly and hard-to-clean rubbery grit, and the thin remainder tore in more than a couple of places. It might possibly be almost "useable" but probably not.
The 1984 was considerably better, although still pathetic, in that the foam was pretty well gone, but the rubbery side was intact and workable. I can probably make it function properly, with some careful jiggling. I am careful and pretty good at making marginal situations viable.
Am I correct in assuming that it would be insanely optimistic of me to imagine that there is any way of getting replacement rubber mats, besides buying Model F 122-key keyboards and taking them apart to see what is inside? Please don't think I am smoking crack or living in La-La Land to even ask.
Probably Monday, I will re-assemble this thing and see what I can make happen. This has been a very difficult week for me (death in the family), and it would be nice if something worked out nicely.
So what was my question(s)? Is the green board better than the copper one, and how do I utilize/improve the rubber mats?
thanks a lot, folks