Restoring a HP9830B calculator.

[Tony Duell]

I have an idea that those PCBs make it a 9866B. That can do lower case and dot graphics, which explains the changes to the shift registers and character generator ROM. Actually, I am surprised the microcode is the same, but...

There are photos of the 9866A boards on the Australian site. The control PCB looks very similar, there are differences in the visible traces round the '123 in the bottom row. But it's close enough that the 9866A schematics should be a big help.

As for the equivalents list, do a search for 'Bench Briefs'. The list was put in a few issues. Note that ICs were removed from the list if no device that was supported used them, so you want to get all the versions of the list you can.