Electric Typewriter Keyboard help

Question

I'm trying to interface my Arduino Uno with a typewriter (smith-corona sl 460) I picked up in a garage sale a year ago. My final goal is to make it so I can type in something on the serial monitor on my computer, and have it come out via the typewriter. I'm going to try to do this by wiring the output pins on the arduino to the keyboard input pins on the typewriter. However, I can't make heads or tails out of this cable coming from the keyboard, and if there are any silkscreen labels, they are on the other side of the board, which I don't want to flip over - I still want this thing to be operational if the hack doesn't work. How would I go about figuring out what line of the cable did which? I have, as I said, an Arduino Uno, as well as a multimeter, and a fairly basic pocket oscilloscope, with no digital analysis or even that much memory past a capture function. If I'm trying the wrong sort of approach for this project, please let me know.

A picture of the cable and the microcontroller:

A picture of the whole board:

Answer 1

What you're likely find for a typewriter keyboard like this is that the keys are simple buttons in a matrix arrangement like this taken from this page about Commodore 64 hardware:

Of course it won't be the same layout it's just to give you an idea of how it's likely to work. To determine the layout you could set your multimeter to continuity check mode (hopefully it has a beep mode) and systematically measure the continuity between pins as every button on the keyboard is pressed, it looks like you should be able to access the pins with the multimeter probes but it'll probably be a two person job so someone else can run through the keys.

It'll be quite tedious but you'll probably find the matrix follows the physical layout of the keyboard somewhat. For example if you start by measuring every combination to find what is shorted when Q is pressed by measuring pin 1 followed by the other 16, pin 2 followed by the other 15 etc and write down the result and then move to W which is to the right and A which is below you should find some sort of pattern starting to emerge so you can work out what the rows and columns are.