7800 color in 2600 games

[7800 Emucoder]

So has anyone ever investigated if it's possible to re-configure or replace certain resistors or otehr components in the 7800 to make the colors in 2600 games appear correctly?

 

I just recently finished up a composite video mode in my recently acquired 2600 jr, and man - I forgot how much different and washed out the color was in 2600 games on the 7800. I mean, really really bad.

 

Anyone?

[Mr SQL]

7800 Emucoder,

the 7800 and the 2600 sound increasingly like the C128 and the C64; the C128 having trouble with some C64 games and having sound that is "different and washed out" like the colours you pointed out made many wish for a C64 instead.

 

It would be interesting to see screenshots comparing game colours on the 7800, the 2600, the Gemini and Intellivision add-on clones, and the different models from the heavy sixer through the Jr. Did your Jr's colours differ under RF before the mod?

[Rex Dart]

I'd like to see comparison shots, too. I've only ever owned a 7800, so I don't know what I'm missing. Maybe it'd be worth my while to pick up a VCS too.

7800 Emucoder, what specific mod did you perform/install?

[7800 Emucoder]

I'd like to see comparison shots, too. I've only ever owned a 7800, so I don't know what I'm missing. Maybe it'd be worth my while to pick up a VCS too.

7800 Emucoder, what specific mod did you perform/install?

it's essentially the same as the "easier 7800 Composite mod", but in the 2600 you need to change the values on the Luma resisitors to compensate for lack of brightness. I will do a picture blog of it in this thread later, and then show comparison photos of the 7800 vs. 2600.

[Shinju]

I have not noticed washed out colors on the 2600 portion in either of my revisions on my 7800's. BUT As far as 7800 games go there is a drastic color difference between the two systems, One looks normal the other one (new revision) has a slight green hue going on.

 

Oh and I play my 2600 games on my Colecovision with the 2600 expantion and they look great I do have a few 2600 jr's and a heavy sixer and a Coleco Gemini and the colors all display nice and crisp on those too.

 

Could be that your 7800 has some old parts that are on their way out and failing, I know when my Turbo Duo was needing a cap job done the colors and sound was all kinds of messed up and once it was fixed it looked better then it did before, probably due to the caps being dried up or almost dried out.

Edited January 15, 2013 by Shinju

[Trebor]

....the other one (new revision) has a slight green hue going on.

 

That is relatively easy to fix. There are two tint/pot adjust in the upper center portion of the 7800 board. The top one (below the cart port) adjust the Maria (7800) color palette hue/tint values the one beneath it adjust the TIA (2600).

 

Only real word of caution is that they are both pretty sensitive. Even a slight adjust will alter the palette, but you are free to turn clockwise and counter-clockwise as much as desired until you get the palette just right.

[Dauber]

I have a later revision 7800...colors on 2600 games look just fine.....

[7800 Emucoder]

That is relatively easy to fix. There are two tint/pot adjust in the upper center portion of the 7800 board. The top one (below the cart port) adjust the Maria (7800) color palette hue/tint values the one beneath it adjust the TIA (2600).

 

Only real word of caution is that they are both pretty sensitive. Even a slight adjust will alter the palette, but you are free to turn clockwise and counter-clockwise as much as desired until you get the palette just right.

That pot doesn't actually adjust proper Tint/Hue values in the conventional Green ~ Red tint adjustment manner. It adjusts Color BIas, so even very slight adjustments alter the color bias tremendously. It turns Brown to Blue and Green to orange. it's not really a good way to adjust tint.

 

The problem with the green push on the newer revision 7800s is the values of the resistors in the Luma ladder. Too strong Luma in the signal skews the overall color balance toward green. Too much chroma skews a bit red, but mostly it just over saturates the picture with color, and colors tend to bleed and smear.

 

What I typicially do in video modded 2600's and 7800's is replace the Lum0 Lum1 and Lum2 resistors in the Luma ladder with 10k or 5k potentiometers and tweak them until it looks better.

Edited January 21, 2013 by 7800 Emucoder

[Trebor]

That pot doesn't actually adjust proper Tint/Hue values in the conventional Green ~ Red tint adjustment manner. It adjusts Color BIas, so even very slight adjustments alter the color bias tremendously.

 

Understood and known. Shinju, however, did not indicate there was not enough red or too little red, just "a slight green hue going on". A slight adjust of the color pot will adjust green so that there is more blue and less green (Something I, on the other hand, should have stipulated just to clarify ).

 

Commando's grass/trees and Pac-Man Collection's Inky are excellent test examples and reference points; typically, while striving for the greenest possible grass and trees, Inky should neither be too green or too blue, but aqua in color.

[Trebor]

What I typicially do in video modded 2600's and 7800's is replace the Lum0 Lum1 and Lum2 resistors in the Luma ladder with 10k or 5k potentiometers and tweak them until it looks better.

 

That is a good idea for those who have the know-how and ability if they have a system with the issue you mentioned. Thanks, 7800 Emucoder

[Phano]

7800 Emucoder, on 21 Jan 2013 - 1:07 PM, said:

 

What I typicially do in video modded 2600's and 7800's is replace the Lum0 Lum1 and Lum2 resistors in the Luma ladder with 10k or 5k potentiometers and tweak them until it looks better.

These are R15, R11 and R12, correct? I'm new to learning all this and I'd like to be sure before I try hacking away at it like a mad scientist.