Atari 800 Monitor Pin-out/Compatibility

[robert_sissco]

I recently got an Atari 800 computer (Not an 800XL, the older 800 model), and I have a question on the pin-out of the monitor port. Is it compatible with the a video cable for a Commodore VIC-20?

I ask because it does not come with a cable for the monitor port, but I do have a cables for the VIC-20, and I see that they use the same 5-pin DIN connector.

I am just asking before I spend $20 on a cable that says it will work with the Atari 800 when i may have a compatible one already hooked up to my monitor.

Thank you

 

[vwestlife]

Yes, Atari and Commodore computers use the same pinout for composite video and audio outputs.

Just be aware that when it comes to luma/chroma video, the pinout differs between Atari and Commodore -- and on the VIC-20, instead of having a luma output, the same pin is used to provide 6 volts DC to power an external RF modulator. So don't attempt to use an Atari luma/chroma video cable on a VIC-20!

 

[robert_sissco]

Yes, Atari and Commodore computers use the same pinout for composite video and audio outputs.

Excellent, I don't have any 5-pin Din Connector luma/chroma cables at all, but I do have composite cables that use that pin out (I just noticed that I did not specify composite in my original post, my bad there), but that you for clarifying that I can use my existing composite video cables for the Atari 800 as I already do for my VIC-20's.

 

[MiaM]

IIRC it's the other way around, kind of sort of.

I.E. a cable for an Atari or a C64 (composite) will work on a VIC 20, but a VIC 20 cable might not necessary work on an Atari or C64. The reason is that the VIC 20 has two pins for composite. The manual vaguely indicates that they have different signal level but every VIC 20 I've seen have these pins tied together.

Thus if someone made a cable for a VIC 20 without any regard for other computers, there is a 50/50 chance that it works on the others if the cable just connects to one of the composite pins. If it for some reason connects to both (perhaps it was easier to solder it that way, labor vise) it might be a bad idea to try it at all.

I assume that all VIC 20 cables have non-molded DIN connectors. Thus it should be easy to pry the locking mechanism so that you can pull the outer sleeve in the cable direction, and then one half of the metal casing will just fall off or at least be easy to lift off, and that will allow you to check which pins are connected (and likely check what they are connected to unless it's a round cable going to a single connector at the other end, say for example a SCART connector or another type of DIN connector or so).

 

[robert_sissco]

I.E. a cable for an Atari or a C64 (composite) will work on a VIC 20, but a VIC 20 cable might not necessary work on an Atari or C64. The reason is that the VIC 20 has two pins for composite. The manual vaguely indicates that they have different signal level but every VIC 20 I've seen have these pins tied together.

The 5-Pin Composite cable that I have works on both my VIC-20 and my C64's with the 8-pin connector. I did test this a while back due to idle curiosity, so I am hoping that even with your additional information that it will work on my Atari 800.

 

[vwestlife]

Thus if someone made a cable for a VIC 20 without any regard for other computers

Unlikely, because by the time the VIC-20 came out, the Atari 800 and TI-99/4 had been on the market for a year, so this created a crop of "Atari/TI/Commodore compatible" composite video cables.

 

[MiaM]

Unlikely, because by the time the VIC-20 came out, the Atari 800 and TI-99/4 had been on the market for a year, so this created a crop of "Atari/TI/Commodore compatible" composite video cables.

Yeah, but especially for a DIY cable, or for that sake a cable manufactured by a local shop, the information about other computers might not had been available at the time.

 

[vwestlife]

Yeah, but especially for a DIY cable, or for that sake a cable manufactured by a local shop, the information about other computers might not had been available at the time.

Of course it's always good to verify the pinout of an unknown DIN-to-RCA cable. For example, there were "Atari monochrome" cables that give you luma only. Plug that into a VIC-20 and you get 6 VDC!

But another reason why VIC-20-only A/V cables are likely very rare is that once the C64 came out, it repurposed the VIC's "video high" output for an audio input. Short that to the composite video output, and you'd get a loud buzz.

 

[MiaM]

Also the 6V is a misprint or misunderstanding that ended up in the documentation and stuck for ages. It's actually the regular 5V rail that powers everything (except parts of the cassette motor circuit) in the VIC 20.