Need help with my Atari 2600 A/V mod

[Need help with my Atari 2600 A/V mod]

Thanks to everyone here, I was able to successfully mod my 2600 Jr. this past weekend. I ended up using Zybex's mod and making the 3 luma resistors and exact 1:2:4 ratio, as well as bumping the next (attenuating?) resistor up to 10 kOhm. I did end up using Air-Sea Battle in B&W mode to see all the luma levels, it's pretty useful actually! The luma level separation still wasn't 100% what I'd like it to be, but it was pretty darn close and you wouldn't notice the difference unless you were comparing the two outputs side by side. I'm going to mod my friend's Atari next, and I think I'll try out the 4050 mod w/o the 4050 chip.

 

I had to play around a bit to get the stereo audio to work with the channel 2/3 switch (for stereo/mono), but now that's up and running as well. I remember seeing a post about how to get stereo, I'll go back to that one and add what I had to do. Thanks again!

[Need help with my Atari 2600 A/V mod]

If it's just a matter of the colors not being bright enough you can just change R4. This doesn't sound like it's for you though, as the whites were too bright. What game(s) do you use to see whites? I just found out that there's an adjustable color pot on the Atari itself so I'll go back to Zybex's original circuit and play around with the pot first.

[Need help with my Atari 2600 A/V mod]

I'm in the process of modding my 2600 jr to output composite video and stereo audio. So far the audio is great and the video works, but I'm not too happy with the colours when I compare them to the original rf. I figured I'd drop a note here to see if anyone could help me out. I also have to say thanks to the various members here who have posted info about the mods I'm attempting.

 

I'm using a transistor circuit, and have tried both the 4050 mod w/o 4050 chip (http://www.atariage.com/2600/faq/index.htm...=2600#composite), as well as the circuit designed by Zybex (http://www.atariware.cl/pixel/sec/eng/2600av.htm).

 

I changed the 4050 mod by taking the chroma signal directly off the resistor on the 2600 and adding it to the combined luma signal (kinda like what was done in the Zybex's mod), then just passed it into an rca jack for composite.

 

In both mods the colours seem to be off. I'm comparing Adventure on two 2600's hooked up to the same tv simultaneously (one unmodded rf, the other one modded composite). I find the greens to be off by quite a bit (more yellowish), and the blues to be a lot lighter, especially for Zybex's mod. I've tried dropping the 3 luma signals in an exact 1:2:4 ratio but it still didn't do the trick. If I bump the 2.7 kOhm resistor in Zybex's mod to 3.7 the blues/purples get better, but the greens/oranges are still off by a lot imo.

 

I can't remember the guy's name, but I've looked at the Video Mod comparison page (quite useful btw!), and I'm definitely not getting the same colours seen in the colour bar pictures (again, I'm comparing the first few screens of Adventure using both rf and a modded 2600).

 

I know this probably all sounds confusing, but I'm just wondering if anyone here has successfully modded an Atari (jr or otherwise) for composite using either of the above mods, and if you had to change anything to get the colours right. Also, if anyone could explain to me what the 3 luma signals actually are I'd also be quite happy. Finally, is there somewhere where I can obtain a couple of copies of this Color Bar Generator? Thanks in advance!

 

Toni

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