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7800 Color Fix!


SoundGammon
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Just looking at the post on the 2600 about "washed-out" color on the 4-switch version of the 2600. Seems a 820 ohm resistor was left off between 2 pins of the TIA chip.

 

Pin 9, color, and pin 6, blanking. It's on the original 2600 and Atari service sent out a memo to install a 820 resistor to bring the color back up!

 

Now, over to the 7800 schematic, SAME THING! No resistor between 9 & 6!

 

I then looked over at the Maria chip video output, pin 43, color, pin 46, blanking---NO CONNECTION, only to the J2 jack which is the external Peripheral Port Output.

 

UNUSED!

 

I don't have any resistors, but I bet a couple of 820 ohm resistors will make it look way better!

 

Anyone want to try it? Can't hurt anything if you know what you're doing!

 

Can someone tell Curt Vendel about this, I'd bet he'd want to try it!

post-7077-0-79236500-1438846520_thumb.jpg

Edited by SoundGammon
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Has anyone tried it yet?

 

If I don't lose my motivation, I'll try it later today on my 7800. It's an early model (AT-84 serial number) with the Expansion Interface. I'll try to take some before/after pics with a game that would show the difference in brilliance/saturation, like Pitfall II.

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Okay, did the 7800 today - I can't see much if any noticeable improvements with my Rev A 7800 board. Not worth even showing pics, to be honest. The weather here has turned storming and rainy since the "Before" pics and the overall change in room lighting might be enough to throw any minimal comparisons anyway. It would be interesting to know if later variants of the 7800 show improvement from this little mod.

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  • 5 months later...

On the TIA, it does help- I actually use a lower resistor to get a little more saturation. I used 200ohm and it looks noticeably nicer, even though you get a little color bleed. It's a nice tradeoff.

 

On the Maria, pin 46 to 43 actually reduces color. However, if you hook pin 47 to 43, you do get a little more saturation. Is the pinout wrong?

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  • 1 year later...

On the TIA, it does help- I actually use a lower resistor to get a little more saturation. I used 200ohm and it looks noticeably nicer, even though you get a little color bleed. It's a nice tradeoff.

 

On the Maria, pin 46 to 43 actually reduces color. However, if you hook pin 47 to 43, you do get a little more saturation. Is the pinout wrong?

Have you left your 820ohm resistor across 43 and 47 on Maria then?

 

Performed it on the TIA and the 7800 looks great now playing 2600 games. Wondering if it's worth doing across Maria now too...

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