Rob Norris

@tpolecat
907 Followers
124 Following
2K Posts

dijkstra would not have liked this

#retrocomputing

Never forget.
Rock on. Serial works in both directions and I can send typos as well as commands (in this case eventually displaying the contents of the status register). Need to tidy up what I have so far, then I'll work on adding some RAM. 5/n
Life! I added a bunch of wires stuff and I now get serial output on reset, which is decoded at the bottom of the oscillogram: CRLF, the PC as six octal digits, CRLF, and an `@` prompt, exactly as expected! Now I need to hook up an RS-232 transceiver and see if I can give it commands from a terminal. 4/n
I can focus much better with paper documentation, so I print out data sheets and old manuals when I know I will be writing notes and flipping around a lot. I have tried using a tablet for this and it doesn't work well for me … e-readers are great for narratives, but not so much for reference materials where the access pattern is kind of random. 3/n
The DCJ-11 processor's ceramic package looks, feels, and sounds like a little bathroom tile. In principle one can hook up a UART and a bit of glue logic and gain access to the operator's console, yielding the world's worst PDP-11 on a few breadboards. It's showing some signs of life, although fewer than I was hoping for at this point. Anyway we'll press on and see how it goes. 1/n
Ok all back together and I think we're good. Would be more fun with a game controller.
The Atari has RF video output, but I didn't have an ancient TV to plug it into so I made a small modification and now it outputs s-video. Seems to be working ok. Now I need to get a game controller.
Nigel takes a break.
A friend brought me an Atari 400 so I’m cleaning it up (pictured) but haven’t been able to test it because it wants 9V AC and I don’t have a transformer that’s the right size. I have run into this kind of thing a few times before and I’m wondering if a variac would work here. Does anyone out there in #retrocomputing land know if they behave ok at low voltages?
Last night I worked on a cap for the "step" button by printing a few layers of white on top, with an asterisk-shaped cutout. I need to do some fine-tuning but I think it's going to work, and it should be much more durable than a sticker.
×
A friend brought me an Atari 400 so I’m cleaning it up (pictured) but haven’t been able to test it because it wants 9V AC and I don’t have a transformer that’s the right size. I have run into this kind of thing a few times before and I’m wondering if a variac would work here. Does anyone out there in #retrocomputing land know if they behave ok at low voltages?
The Atari has RF video output, but I didn't have an ancient TV to plug it into so I made a small modification and now it outputs s-video. Seems to be working ok. Now I need to get a game controller.
Ok all back together and I think we're good. Would be more fun with a game controller.
@tpolecat that’s amazing!
@davbucci
I believe the 9V AC is immediately turned to DC by a rectifier inside. You should be able to fers it DC just fine. In that case polarity won't matter. Ill look around for confirmation.
@tpolecat

@davbucci
https://retrorepairsandrefurbs.com/2023/02/04/1982-atari-400-repair-restoration/
If this is the same as yours the 9V AC is rectified and regulated to 5V and 12V.

9V AC is about 12.7 RMS and the transformer probably put out much more until fully loaded. The 7805 needs 7 to 35V and the 78M12 needs 14 to 35V. Feed it 14 to 16V DC and you should be good to go.
@tpolecat

1982 Atari 400 Repair & Restoration

Believe it or not, I’m known around my workplace as a bit of a geek, primarily because of the tinkering around with vintage electronics that I do in my spare time – as such, every now a…

Adam's Vintage Computer Restorations
@maker_tom @davbucci Cool, thank you! I managed to find a 9V transformer but I will keep this trick in mind for next time.