I restored a HP9100A and B. They are from the dame eara. That is, one I managed to repair, the other showed some sings of live, (but it was found under a floor, near sea, and showed signs of salt water). No sevice manuals, a big collection of hand-drawn schematics made by tony, the authority in 9100 land, but very hard to follow and project to actual pcbs. Everything was current driven that made probing not easy. The very rare, short, electrostatic CRT that was broken in the B version. Most common problem with these beasts.
This is a cutting edge calulator, the first programmable sceintific calculator (it even can do complex numbers)
I made a lot of pictures and it is made very interesting. It has hundereds of transistors and diodes. uses core memonrie and, a magnetic card reader. But on the other hand was the first use of teflon as pcb and some boards are multilayer with many layers.
If I understand well the ROM was made by a multilayer pcb which formed a matrix of crossing wires to makle some sort of replacement for core memory.]
If you can lay your hands on one it could be footage for an interesting tear down video. I do not have them anymore. I restored them for a museum.
http://www.pa4tim.nl/?p=3964 The 9100A that was very easy to fix
http://www.pa4tim.nl/?p=3878 The 9100B with lots of detail pictures. I got it to work with a round tube that fitted the cabinet more or less. But it seemed like the rom was gone. The crt showed some activity, it seemed to react to operators but it made no sence, After 2 months I gave up.
The multilayer teflon board :
Some of the > 1000 diodes in this thing