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