Dejan Levec

Old Epson “Printer”

Today I was searching for something at home and stumbled upon old printing calculator, that hasn’t been in use for a few years.

Firstly, I plugged it in the wall socket and tried pressing different keys to see what it can do. Since I don’t really know how to use it, only thing I got were some random numbers printed on paper.

Secondly, I started thinking what I can do with it … well, I can at least open it to see what’s inside.

Picture below shows how it looks inside. On the upper right there is a mains transformer which has two outputs, first one is probably for micro controller and logic circuit and outputs about 6V, and the second one has output of approximately 22V and might be used to drive printer and display.

On the upper left there is a numeric printed which is surprisingly made by Epson.

On the middle/bottom part there is a logic board with the screen and a second board which holds keys.


Logic board has Mitsubishi 8-bit micro controller MS50754-125SP which has (according to datasheet) 6144 bytes on ROM and 160 bytes of RAM and apart from supply circuit it also features three Mitsubishi Darlington transistor arrays M54531P which are used to control numeric printer.

I don’t really have any use of screen and keyboard, but printer looks quite interesting. I don’t really know how much time will I have in the near future, but I would really like to control this printer from micro controller/computer.

Click here for more pictures of the printer

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