Latest 7800 project

[AtariAwesomeness!]

This started as a completely blank pcb from best electronics. Just finished it and it works great. Looking for opinions.

[Trebor]

You have the newest 7800 console out there...

 

Very cool and great job!

[+sramirez2008]

Looks great! Please hook it up to a CRT and show us a picture of it running a game or two.

[AtariAwesomeness!]

Sorry don't have a crt. Here is ikari warriors and commando on my plasma

[Trebor]

Sorry don't have a crt. Here is ikari warriors and commando on my plasma

 

Adjusting the tint/hue on the Plasma will yield a much better picture for Commando and Ikari Warriors.

 

Leaving a modern display at default tint/hue yields a very overly green looking dirt, due to the nature of the hue "brown/tan" (range) being utilized for Commando and Ikari Warriors being highly sensitive, strongly contingent on the default tint/hue setting of the display device.

[AtariAwesomeness!]

Adjusting the tint/hue on the Plasma will yield a much better picture for Commando and Ikari Warriors.

 

Leaving a modern display at default tint/hue yields a very overly green looking dirt, due to the nature of the hue "brown/tan" (range) being utilized for Commando and Ikari Warriors being highly sensitive, strongly contingent on the default tint/hue setting of the display device.

Thanks for letting me know. I was wondering about that. I adjusted the color pots using diagnostic cart.

[AtariAwesomeness!]

Thanks again Trebor

[Dauber]

Leaving a modern display at default tint/hue yields a very overly green looking dirt, due to the nature of the hue "brown/tan" (range) being utilized for Commando and Ikari Warriors being highly sensitive, strongly contingent on the default tint/hue setting of the display device.

 

Whoa...does that explain why Donkey Kong looks green on my 7800???

[Trebor]

Whoa...does that explain why Donkey Kong looks green on my 7800???

Short Answer:

Yes.

 

Long Answer:

Donkey Kong's fur specifically utilizes the value $F3. The Hue range $Fx is one of three hue ranges across Atari consoles in which a resulting shade of color can vary quite noticeably. The other two ranges are $Ex and $1x.

 

-$Fx and $Ex = Impacted greatly by tint/hue setting of the display device AND how "warmed-up" is the console.

 

-$1x = Impacted greatly by tint/hue setting of the display device ONLY. The appearance of the colors will not change regardless of console "warm-up".

 

The Kicker:

Color calibration of the 7800 console (Color pot closest to the cartridge port on the motherboard) is contingent on matching a $Fx value with a $1x value. This inadvertently can cause a very strongly calibrated green looking palette if the $1x reference is leaning green, as $Fx will be configured that way as well.

 

The Fix:

Hue range $1x should not lean green or chartreuse (Green-yellow); instead, it should appear as a true gold/golden range. The dark end of Hue $1x range should be a true brown (Not dark hazel), the light end a bright yellow (Not yellow-green).

 

Hue $1x is highlighted below, taken from the Color Demo Cart and from RevEng's utility cartridge, exemplifying a properly calibrated color pot:

 

 

Ensuring Hue $1x is in the golden range first on the display being utilized, then calibrate the color pot on the 7800 console, avoids an overly green appearing palette.

 

Where "warm-up" fits into the picture ultimately and ideally, after color calibration is performed, a consistently running console demonstrates the Hue $Fx range appearance as falling between the shades of Hues $1x and $2x. This provisions a full 256 color palette:

 

 

Some/Most consoles are color calibrated rather quickly though; consequently, when the console is completely warmed-up, the end result is $Fx (closely) matching $2x, and $Ex (closely) matching $1x: