13 replies to this topic

[snstay]

I just hooked up my 7800 and the colors dont seem as vibrate and bright as my 2600. Is this normal or is there something i can do to fix it. Or do i just deal with it?

[Mitch]

It's pretty much normal.

Mitch

[Atari Joe]

I crack that sucker open and start twisting that little dial around thats in there that lets you fine tune the colors the way you want them. I love the 7800 as my favorite system or maybe the Lynx but sometimes the colors just look dull compared to NES and SMS.

What I do is mess with that dial inside the board and then also set a color preference profile on my tv screen the way I like it so the colors on the 7800 look the way I want them to. Sometimes when it comes to stuff like this I find myself wishing the 7800 was a better system than it really is.

[Underball]

That dial is a color bias/hue control. It has nothing to do with the color brightness or saturation.

[Tubular Gearhead]

Underball, on Thu Jun 9, 2011 7:07 AM, said:

That dial is a color bias/hue control. It has nothing to do with the color brightness or saturation.

+1 You need to change a few resistors and switch a few things around if you want to fix the way the 7800 displays "dull" 2600 colors.

[SlowCoder]

Tubular Gearhead, on Thu Jun 9, 2011 9:41 AM, said:

You need to change a few resistors and switch a few things around if you want to fix the way the 7800 displays "dull" 2600 colors.

Any documentation on this?

[Underball]

Tubular Gearhead, on Thu Jun 9, 2011 9:41 AM, said:

Underball, on Thu Jun 9, 2011 7:07 AM, said:

That dial is a color bias/hue control. It has nothing to do with the color brightness or saturation.

+1 You need to change a few resistors and switch a few things around if you want to fix the way the 7800 displays "dull" 2600 colors.

Yeah, I know it's not hard, but does anyone have a wiring schematic for doing this mod? I'd love to do it while I have some free time coming up.

[Tubular Gearhead]

Underball, on Thu Jun 9, 2011 2:49 PM, said:

Tubular Gearhead, on Thu Jun 9, 2011 9:41 AM, said:

Underball, on Thu Jun 9, 2011 7:07 AM, said:

That dial is a color bias/hue control. It has nothing to do with the color brightness or saturation.

+1 You need to change a few resistors and switch a few things around if you want to fix the way the 7800 displays "dull" 2600 colors.

Yeah, I know it's not hard, but does anyone have a wiring schematic for doing this mod? I'd love to do it while I have some free time coming up.

I don't have a schematic. There might be some floating around the internet. I do have a basic diagram of where the problem is and what needs to change.



The 2600 signal is compromised so that when in 7800 mode there will not be interference. The value of R17 is too high (low signal) to allow good colors. They should have used a switch (like I show in diagram) or an "OR GATE" like U3 to toggle between the chroma signals instead of just crippling the 2600 signal. The luma ladder values are a little high for a simple video amp. I cut all their values in half. I disconected the RF completely. My 7800 is just as bright in 2600 mode as a heavy sixer...

I know this post isn't complete, but I hope it helps a little.

[Mr. Do!]

snstay, on Wed Jun 8, 2011 7:32 PM, said:

I just hooked up my 7800 and the colors dont seem as vibrate and bright as my 2600. Is this normal or is there something i can do to fix it. Or do i just deal with it?

I raised this issue way back in the 90's on Usenet. I received 2 answers back then:

1) Replace the chroma/saturation circuit in the 7800.

2) Adjust the color pot for the 2600 in the 7800 (supposedly it has 2 pots, one for 7800 games and one for 2600).

I never bothered doing either. I noticed the difference when I finally hooked up a 2600jr after exclusively playing 2600 games on my 7800 for many, many years. I stuck with the 2600jr because I didn't have to alter carts (like the Tigervision games) that wouldn't fit in the 7800 anyway.

[Tubular Gearhead]

Mr. Do!, on Fri Jun 10, 2011 8:36 AM, said:

snstay, on Wed Jun 8, 2011 7:32 PM, said:

I just hooked up my 7800 and the colors dont seem as vibrate and bright as my 2600. Is this normal or is there something i can do to fix it. Or do i just deal with it?

I raised this issue way back in the 90's on Usenet. I received 2 answers back then:

1) Replace the chroma/saturation circuit in the 7800.

2) Adjust the color pot for the 2600 in the 7800 (supposedly it has 2 pots, one for 7800 games and one for 2600).
I never bothered doing either. I noticed the difference when I finally hooked up a 2600jr after exclusively playing 2600 games on my 7800 for many, many years. I stuck with the 2600jr because I didn't have to alter carts (like the Tigervision games) that wouldn't fit in the 7800 anyway.

Answer #2 (bold) has been around for a while is not correct. See post #4. Adjusting this knob can correct an issue with the color HUE, but will not get you the result you are looking for.

Answer #1 works.


FWIW, the plastic cartridge guide on 7800's is terrible. I took mine out, put it in a mill, and removed the squared off corners and other obstacles to tight cartridges. Never modify the cartridges!

[Underball]

Tubular Gearhead, on Thu Jun 9, 2011 4:49 PM, said:

Underball, on Thu Jun 9, 2011 2:49 PM, said:

Tubular Gearhead, on Thu Jun 9, 2011 9:41 AM, said:

Underball, on Thu Jun 9, 2011 7:07 AM, said:

That dial is a color bias/hue control. It has nothing to do with the color brightness or saturation.

+1 You need to change a few resistors and switch a few things around if you want to fix the way the 7800 displays "dull" 2600 colors.

Yeah, I know it's not hard, but does anyone have a wiring schematic for doing this mod? I'd love to do it while I have some free time coming up.

I don't have a schematic. There might be some floating around the internet. I do have a basic diagram of where the problem is and what needs to change.



The 2600 signal is compromised so that when in 7800 mode there will not be interference. The value of R17 is too high (low signal) to allow good colors. They should have used a switch (like I show in diagram) or an "OR GATE" like U3 to toggle between the chroma signals instead of just crippling the 2600 signal. The luma ladder values are a little high for a simple video amp. I cut all their values in half. I disconected the RF completely. My 7800 is just as bright in 2600 mode as a heavy sixer...

I know this post isn't complete, but I hope it helps a little.

Ok. so let me see if I follow properly here:

R16 and R17 get combined, so you replaced R17 with a lower value resistor, (maybe 2.2k?) and then put a toggle switch in between the combiation point, so that the now higher TIA chroma output wouldn't bleed and cause intereference?

Makes sense. I will have to warm up the soldering iron and have a go at it. I could hide the toggle under the side, next to the A/V ports I added from the composite mod.

Sweet.

[Tubular Gearhead]

Underball, on Fri Jun 10, 2011 10:29 AM, said:

Ok. so let me see if I follow properly here:

R16 and R17 get combined, so you replaced R17 with a lower value resistor, (maybe 2.2k?) and then put a toggle switch in between the combiation point, so that the now higher TIA chroma output wouldn't bleed and cause intereference?

Makes sense. I will have to warm up the soldering iron and have a go at it. I could hide the toggle under the side, next to the A/V ports I added from the composite mod.

Sweet.

Yep, basically that is it. After that, if you want composite out just insert your favorite amplifier circuit of choice at the point where is says "C video J2-3" right before the RF modulator, disconect the RF if you wish (cleans up the picture still and unloads the circuit a little), and away you go. I also disconected the sound mixer circuit for the RF (I believe removing C9 does the trick), as you dont need to be mixing sound with picture any more if you toss the RF box. I put my amplifier board where the old RF box was.

Cheers!

Edited by Tubular Gearhead, Fri Jun 10, 2011 11:07 AM.

[Underball]

Tubular Gearhead, on Fri Jun 10, 2011 10:59 AM, said:

Underball, on Fri Jun 10, 2011 10:29 AM, said:

Ok. so let me see if I follow properly here:

R16 and R17 get combined, so you replaced R17 with a lower value resistor, (maybe 2.2k?) and then put a toggle switch in between the combiation point, so that the now higher TIA chroma output wouldn't bleed and cause intereference?

Makes sense. I will have to warm up the soldering iron and have a go at it. I could hide the toggle under the side, next to the A/V ports I added from the composite mod.

Sweet.

Yep, basically that is it. After that, if you want composite out just insert your favorite amplifier circuit of choice at the point where is says "C video J2-3" right before the RF modulator, disconect the RF if you wish (cleans up the picture still and unloads the circuit a little), and away you go. I also disconected the sound mixer circuit for the RF (I believe removing C9 does the trick), as you dont need to be mixing sound with picture any more if you toss the RF box. I put my amplifier board where the old RF box was.

Cheers!

Already have the "Easier 7800 composite video mod" in place.

When I get some time, I will play around with this and post results. Maybe even add this to the Easier 7800 video Mod Thread as an addenda.

[snstay]

So maybe if i get a s video mod it might help the dull colors?