SoundGammon Posted August 6, 2015 Share Posted August 6, 2015 (edited) 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! Edited August 6, 2015 by SoundGammon 1 Quote Link to comment Share on other sites More sharing options...
SoundGammon Posted August 6, 2015 Author Share Posted August 6, 2015 (edited) Here's the original 2600 TIA schematic and the memo: Also, thanks to DrVenkman for bringing this to our attention! Edited August 6, 2015 by SoundGammon Quote Link to comment Share on other sites More sharing options...
JFD62780 Posted August 6, 2015 Share Posted August 6, 2015 I may not own a 7800, but I think this Tech Tip topic marvels a sticky. You think, back in the day, a recall mighta saved the quality of this product, at least? 1 Quote Link to comment Share on other sites More sharing options...
R.Cade Posted August 6, 2015 Share Posted August 6, 2015 Has anyone tried it yet? Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted August 6, 2015 Share Posted August 6, 2015 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. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted August 6, 2015 Share Posted August 6, 2015 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. 1 Quote Link to comment Share on other sites More sharing options...
SoundGammon Posted August 6, 2015 Author Share Posted August 6, 2015 Are you trying the resistors on both TIA & MARIA? Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted August 6, 2015 Share Posted August 6, 2015 Are you trying the resistors on both TIA & MARIA? Only TIA. Color on my 7800 games is pretty good, actually. Quote Link to comment Share on other sites More sharing options...
SoundGammon Posted August 6, 2015 Author Share Posted August 6, 2015 When I get some resistors, I'll try it on my "Pure" 7800 system. What that is, I removed U3 where the summing of the 7800 & 2600 went before the RF box. I put jumpers where the 7800 lines went. Can't play 2600 games on it, but I didn't get a 7800 to play 2600 games anyway! Quote Link to comment Share on other sites More sharing options...
R.Cade Posted January 16, 2016 Share Posted January 16, 2016 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? Quote Link to comment Share on other sites More sharing options...
cjameslv Posted January 22, 2016 Share Posted January 22, 2016 I'd be interested in doing this. What is pins 46 & 47 labeled as though? Quote Link to comment Share on other sites More sharing options...
+save2600 Posted February 2, 2017 Share Posted February 2, 2017 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... Quote Link to comment Share on other sites More sharing options...
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