I have the printer unit from an old desktop printing calculator that I would like to build an interface to. It's made by NMB, and the model number could possibly be 212-1550FG or 279486 (these numbers appear on the chassis), but I can't find any info on the Internet.
This one is an 18 column printer, numbers and math symbols only. It doesn't appear to have any interface electronics, just a 27 conductor ribbon cable for connection back to the main calculator PCB.
It uses a stack of 18 print wheels, one motor, lots of gears, a couple of shaft position sensors, a few trip levers and solenoids for tripping paper advance and print head, plus (I assume) 18 solenoids (hidden inside) for tripping the print wheels. I think I understand the logic of how it works, but not the voltages involved.
I was wondering if anyone has any experience with these things.
Edit:
I still have the original calculator, but it's not working. However, after poking at it for a while, I managed to get it to power the printer, and I took some voltage readings. It appears that everything operates on 15 volts. I can probably work out the rest now.
BTW, the CPU is a NEC D1251G 'calculator on a chip' circa early 1980's. Can't find any info on it. I suspect it's one of those old MOS devices that requires several voltages.