Change in computers as a hobbiest... 2836

Jukka Aho

Well, it was not "built from scratch". I bought a video card kit. This was a single printed circuit card which contained a uart chip, some static memory chips, two 5x7 character ROM's (upper case and lower case) and a bunch of SSI parts to generate a video signal. To this I added a keyboard kit (George Risk). Both of these were kits, you got a bag of parts and had to solder them onto the printed circuit cards. I built the 5 Volt power supply and already had a small +-- 12 volt supply on another printed circuit card which I had previously used as a "lab supply". I then built a small kludge board which had a dip switch on it to select some terminal characteristics like baud rate and stop bits and had the TTL to RS232 conversion chips on it to interface between either the modem or one of my hobby computers and the TTL serial data coming from the video card kit (Cybernex 6416). All this was screwed down flat on a piece of 3-4 inch plywood 17"x24". As the video card kit, keyboard kit, +-- 12 volt power supply and my kludge board all had edge connectors I built a wiring harness which interconnected and plugged into all of these cards. After a couple of years, I started using this to dial into a PDP-11. PDP's liked to use square brackets and the Risk Keyboard kit (model 753) did not have those keys on it. However, the keyboard encoder on the keyboard kit did generate them and the appropriate leads had been run to the edge connector. So a bought a couple of additional George Risk key switches and the two keycaps for them -{ and -}and using those tiny EZ Hook clip leads added those two keys to the unit. You couldn't touch type with them as they're just lying there but the square brackets were just needed to log in. (This was before I became a C programmer and so the braces were at the time useless :-) As originally built there was one additional tiny circuit card which was a video oscillator which took the video signal and turned it into channel 3 or 4 which I then displayed on my Black and White television. With this, however, it was hard to tell the difference between B and 8 on the screen (and when you're looking at HEX dumps, this is important :-) so I eventually bought a small 9 inch video monitor which would accept the video signal directly with the expected improved quality of the image. (And now I could also watch TV and compute at the same time :-) Although I haven't used it in years, its in the closet in the next room and I just got it out to verify a couple of the facts above.

I suspect that many computer hobbyists of the mid to late 1970's would have a similar story to tell.

Chris AN GETTO$;DUMP;RUN,ALGOL,TAPE $$