Recently I have been considering writing some of the stories of my life down, in the hopes that someone may find them interesting.

This page is where I am going to dump stories as I think of them, or as I tell them to others. Needs lots of cleanup

Atari 400

I finally got my own computer, an Atari 400, with a basic cartridge and a cassette drive!

Shelled walnuts all summer to save enough $$ to buy a floppy drive for it. (a Rana 1000, which could do double density, a whopping 360K on a double sided floppy).

Also added an memory expansion, from 16KB to 48KB.

Later I hand soldered a surplus keyboard I found to work with it instead of the membrane keyboard, added a swtich to turn off keyboard click, and added an audio output jack (since the 400 only had RF out).

Attaching my own keyboard to it was quite a learning experience.
The keyboard connected to the motherboard via a ~25 conductor ribbon cable.
So I unplugged that and took a piece of wire and poked it into the holes in various combinations until I had mapped what pins to short to enter each key.
I picked up an old keyboard at a computer swap for a buck, opened it up, cut various traces and soldered wires onto them in the matrix needed.
When I connected it and pressed keys, nothing happened. It didn't work at all. Puzzled, I took it back apart, and tried typing by directly shorting the pads with a jumper. That worked fine. It just didn't work when I tried to use the bottom of the key. Evetually I put a ohmmeter on the bottom of the keys and discovered they weren't conductive.
I had no idea what that meant, but solved the problem by glueing aluminum foil to the bottom of each key.
Worked great. I did have to disassemble and clean it every few months, though.
Years later I learned what a capacative scan keyboard was (an OH! so that's why that keyboard was like that moment).
There was one other thing I did on that keyboard: it had dedicated cursor keys, which the Atari 400 didn't. You had to hold down the ctrl key to turn other keys into the cursor keys.
I wanted to use the dedicated keys, so I cut the pads on the board in half, wired one side to the ctrl key, and the other side to the keys used for cursoring. Then I built up solder towers on the ctrl side so that it engaged first, before the cursor key.
Worked fairly well, although it was usually the first to start failing when it became time to clean it.

-- KevinSeghetti - 23 Nov 2011

Topic revision: r1 - 23 Nov 2011 - 21:10:16 - KevinSeghetti

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