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4-port upgrades


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1 hour ago, AtariHobbyLover said:

Unfortunately, the only way I am aware of getting audio is the top of R12 in the CX-55. This is a direct connection to pin 12 of the TIA, 444D chip. I tried to test pin 30 on J1 in the 5200 for audio and that did not work either. It's labeled as OSC.

Hm, OK.  I'll go back and check the schematics again when I'm at home; my memory could well be off.

1 hour ago, AtariHobbyLover said:

If you have a 4-port that you personally modded for the VCS adapter, the green wire you add to pin 30 and the other end to the middle of that 6 component assembly, per the install instructions, is suppose to be for audio.

Ah - I'm working with a 2-port 5200.  Don't have any 4-ports and have never performed the compatibility mod, so have no practical experience with it.  However, that's an interesting bit of information.  I'll add it to the 'to check' pile for when I'm back.

1 hour ago, AtariHobbyLover said:

Before I even added the UAV to the CX-55, I got audio on RF whether I had the green wire connected or not. That leads me to believe Pin 24 is carrying both audio and comp video to the 5200.

Got it.  Also added to the pile.

1 hour ago, AtariHobbyLover said:

I also don't believe the 5200 has a separate leg for audio going into the modulator.

That one I'm not 100% certain is correct.  My recollection is that video mixes to composite before entering the modulator, and audio is mixed with video within the modulator.  Again, though, I'm saying this without the schematics at hand so could well be mistaken.

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On 7/30/2023 at 10:18 AM, AtariHobbyLover said:

I think audio is possibly being mixed in with the video because it gets injected directly into the RF modulator in the 5200.

Got home, looked at the schematics for both the CX55 and the 5200, and it does appear that this is the case.  For some reason I had it in my head that audio was being carried separately, but it and video appear to be being combined before leaving the CX55 and subsequently being injected directly into the 5200's modulator.

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8 hours ago, AtariHobbyLover said:

Probably the reason no one has figured this complex puzzle out yet.

That and the lack of unused pins on the cartridge port.  There's just not enough of them to bring over all of the needed signals without doing some significant surgery.


At this point, the two best ideas I have both involve implementing an interconnect between the CX55 and 5200 to carry the A/V signals from the adapter to the console.  This idea may get some attention later in the month, time permitting.  Parts are on order, but it's fairly low-priority for me.


This isn't as much a case where there's a good way or a bad way to do things, but rather a bunch of different ways that all have their own shortcomings in one way or another.

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