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.
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.
Last edited: