The standard for video output on 8-bit computers is there was no standard. Well, oddly enough, a bunch of companies did something super similar, but there are enough gotchas that you have to be careful. At least Atari sidestepped the problem. Here’s my experience with Atari 800 video cables, which also (mostly) applies the XL and XE variants. And you can use the same cable with other machines in a pinch.
Premium Atari video cables
If you want the equivalent of a Monster Cable for your Atari 8-bit, contact Best Electronics. For a little over $20, they’ll sell you a no-compromises version of whatever you want. And for what you’re getting from them, it seems like a fair price. The build quality is similar to Monster, without the ludicrous claims and the crazy markup. The main thing they brag about is how they drove their manufacturer nuts in developing it.
But that’s not what I’m here to talk about. I’m here to talk about a cheap-enough, good-enough solution with some versatility in the types of displays it works with, and that can also, with caveats, work with other computers and early Sega game consoles.
The 4-plug MIDI to RCA cable on an Atari 800
For a good-enough solution that only costs a few dollars, get yourself a MIDI to RCA cable. I paid around $6 for mine, which is 1/3 what a similar cable costs from a computer dealer. A MIDI cable works because pin 2 is ground, the same as an Atari. When you get the cable, double-check with a multimeter. Make sure the outside of the RCA plugs is connected to pin 2 (the center pin) on the DIN connector.
The cool thing about these 4-plug cables is you can get either standard composite out of an Atari 8-bit or, in the case of systems like the Atari 800, separated composite with chroma and luma signals like S-Video. That’s just like a Commodore 64, so you can connect an Atari 800 or XE to the excellent Commodore 1702 monitor. Of course other 1980s monitors had this capability, particularly Magnavox monitors, but the Commodore 1702 was the most reliable in my experience and will probably be easiest to find.
Mapping out the cable
Unfortunately there’s no standard for the color codes. You’ll have to either map them out with a multimeter to figure out what pins do what, or do some trial and error. If you want to use the multimeter, pin 3 at 3 o’clock is audio. Working clockwise, the next pin is pin 5, chroma on the 800 and the XE. It’s not connected on the XL unless someone modded it. Pin 2, at six o’clock, is ground. I hope you already tested that one. Pin 4, at 7 o’clock, is standard composite video. Finally, pin 1, at 9 o’clock, is luma.
I wrote labels out on pieces of tape and put them on all of my wires.
With an Atari 800, you can get away with trial and error. Plug in a game cartridge that makes some noise and try it out. The video plugs won’t make a sound, or will emit odd sounds if you plug them into the audio jack. Luma will give a monochrome display or no display if you plug it into a composite input. Chroma will give either an odd display or no display. The composite display can sub in for Chroma in a pinch on an XL machine. It won’t look quite as good as separated composite but it works.
The 4-plug MIDI to RCA cable on other machines
Lots of other machines use a very similar connector, such as the Commodore VIC-20, C-64, Texas Instruments TI-99/4A, and Sega Master System and Genesis game consoles. But there’s a caveat with each of these systems. The Atari 800 and XE are the only systems that can use this cable with no caveats.
On US versions of the TI-99/4A, pin 3 at 3 o’clock outputs audio. Pin 5 is not connected. As usual, pin 2, at 6 o’clock, is ground. Pin 4, and 7 o’clock, is composite video, the same as Atari. Pin 1, at 9 o’clock, outputs 12 volts DC to power an RF modulator. Label this plug as dangerous on a TI.
The European version of the TI-99/4A doesn’t output composite video so I won’t cover that one here.
If you do the trial-and-error thing, check every plug with a multimeter first, and mark the one that gives you 12 volts.
Incredibly, the VIC-20 uses the same pinout as TI, just differing on the voltages. Pin 3 at 3 o’clock outputs audio. You can ignore pin 5, which is not connected. Pin 2, at 6 o’clock, is ground. Pin 4, at 7 o’clock, is composite video, the same as Atari. Finally, pin 1, at 9 o’clock, outputs 5 volts DC to power an RF modulator. Label this plug as dangerous on a VIC.
If you do the trial-and-error thing on a VIC, check every plug with a multimeter first, and mark the one that gives you 5 volts.
The C-64 and 128 don’t have any dangerous voltages like the VIC, but pin 5, at 4 o’clock, is the audio input to the SID chip. You don’t want to touch that plug if you have a 4-plug connector connected to your 64 or 128, because SID chips are getting crazy expensive. Commodore put the separated composite lines on other pins on an 8-pin DIN, and you’re better off using one of those cables on a 64.
Because of the SID input, I don’t recommend the trial and error approach with the 64 or 128. There’s too much risk of damaging your SID chip.
Sega Genesis and Master System
A 5-pin plug fits the Genesis and Master System, but the mapping is completely different. Pin 3, at 3 o’clock, is composite video. At 4 o’clock, pin 5 is an RGB signal, not useful for these purposes. Pin 2, at 6 o’clock, is ground. At 7 o’clock, pin 4 is the dangerous one, so mark that plug as unsafe for Sega. Pin 1, at 9 o’clock, is audio.
If you do the trial-and-error thing on a Sega, check every plug with a multimeter first, and mark the one that gives you 6 volts.