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Some snow on Atari 2600 rgb connection

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#1 Reality Studio OFFLINE  

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Posted Sun Jan 7, 2018 3:10 PM

Hey guys, I had my 2600 modded by someone on this forum for both s-video and rgb out. I had only tested the s-video out when I got it and that works perfect, but I just recently got a scart converter to try the rgb out and the quality on that is kinda poor. Basically it has snow or interference patterns on it. I know it's not because of the scart converter because I tried that with my Sega Genesis as well and that's perfectly clear.


I'm thinking of popping it open to see if it's an easy fix, but offhand would you guys know what it could be? Like maybe a simple grounding issue or something like that? Or could it be due to the 2600->Scart cable I'm using? I'm using the one he supplied way back when he modded the machine for me.

Edited by Reality Studio, Sun Jan 7, 2018 3:11 PM.

#2 BassGuitari OFFLINE  


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Posted Sun Jan 7, 2018 3:22 PM

That's the 300-ohm/rabbit-ear RF simulator. :-D :P

#3 H454 OFFLINE  



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Posted Mon Jan 8, 2018 12:26 AM

Are you running the sound through (what I'm assuming is a genesis jack) as the video?


The RGB instructions recommend running the sound out separately due to interference.

#4 iesposta ONLINE  


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Posted Mon Jan 8, 2018 1:11 AM

I have the RGB kit, but I haven't installed it yet.

The above, "The RGB instructions recommend running the sound out separately due to interference." may be what you seek.


Do you have a Framemeister up-scaler?

Those come with a Japanese SCART, so you need to use Japanese to Japanese (to up-scaler), -OR-  Euro to Euro (to up-scaler).

You can not mix the Japanese SCART with the Euro SCART. I don't think that's your problem though...


(I have the 2 Euro SCART connectors on my PlayStation 2, and the RGB is absolutely stunning, however some titles that can output 480p benefit from Component YPbPr (because supposedly RGB can't do 480p?)) Also Sony blocks RGB for playing DVD's unless you use DVD Region Free software disc or use a PC to sign an .elf DVD Progressive Scan player and put that on a Free McBoot memory card.


For my original Sega Genesis (the one with the great sound), I did an easy S-Video on both the main unit, and the 32X attachment.

That's been good enough for my purposes.

It is just one transistor and 2 resistors. I even found everything in scrap 80's electronics, so the cost was $0.

The output through the 32X is MUCH nicer. I guess it just has a cleaner video signal.

The 32X S-Video is a bit tricker because one solder point is very small and thin and it is easy to have solder end up on more than one trace.

The sound from the Genesis should always come from the front headphone connector, unless the person modding it has routed them to the back as white / red RCA audio jacks. If you don't use the headphone output, sometimes you will not get a stereo signal.

It's a giant mess of wires, but "real hardware all the way!"


TheGoldenAx used to make a Sega power supply from a Nintendo brick that had 3 power outputs.

One for the Genesis, one for the 32X, and the other for the CD attachment.

#5 iesposta ONLINE  


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Posted Mon Jan 8, 2018 2:11 AM

About 2600 sound.

The console is so large because it was to have 2 stereo speakers in the console.

That got scraped, and they combined the left and right channels and sent it out through the RF TV signal.


USA NTSC TIA Pin 12 and 13 have the 2 sound channels.

If you pull the signal from those pins, each through a 10uF capacitor to the connector, then the connector to ground, you'll get what they call "2-channel mono".

[ Pin 12 to 10uF ceramic, or "-" of 10uF electrolytic capacitor, to RCA white (left) connector (center), then the outer (barrel) RCA to any ground point. ]

[ Pin 13 to 10uF ceramic, or "-" of 10uF electrolytic capacitor, to RCA red (right) connector (center), then the outer barrel RCA to any ground point. ] 


The early games, like Combat, were programmed taking these 2 channels into account.

For instance, the tank on the right will come out the right speaker, the tank on the left will come out the left speaker.

There's no logic when both players cross to the other side, however. The original right tank audio will still come out the right speaker, even if it's all the way on the left side.


SpeceWare's remake of Warlords called "Medieval Mayhem" uses this stereo effect. Hits on screen right come out the right speaker, hits on the left come out the left speaker. And the intermission when the winning Knight makes his walk across the screen waving his colored flag, the audio follows (I think).

I hope "Medieval Mayhem" is one of the titles you purchased from the AtariAge store. It's like comparing "Asteroids" to "SpaceRocks". That much improved.


Attached File  mm20071129NTSC.bin   32KB   20 downloads


And "Star Castle Arcade" is another one that is near arcade accurate.

There was a programmer who made an 8K version, to show to himself it could have been done, and not turned into Yars' Revenge (which was to to be Star Castle).

When asked about sharing or purchasing his version, he declined, but with urging he finally settled on $32,768, which is when I suggested we make a great version.

A few months later we HAD a great version shaping up. So programmer 8K decides to do a Kickstarter. He managed to get 418 people to pledge $23,946 and still had to manufacture 375 carts, boxes, stickers, LED's (yes the cart lights up during explosions), instructions, and mailing.


Some people find regular gaming with the 2-channel audio split to be annoying.

You can use a Y-cable or a simple mixing board to combine the 2 separated channels back into 1 mono channel and send it to both speakers.  

#6 Reality Studio OFFLINE  

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Posted Mon Jan 8, 2018 8:56 PM

Hey guys thanks for the info. It's actually a mini din connector, much smaller than the one on the Genesis, and it does have sound routede through it. I didn't do the install, I paid someone on Atari Age to do it for me, From the looks of it seems like I'd have to open the console and disconnect the audio part going to the din cable. I don't have a Framemeister, just a cheaper euro scart to hdmi converter that I got on Amazon which works great with my Sega Genesis. It does not have an audio in though (just scart in) so even if I disconnected audio on the rgb part, I'd have no way to route audio through that converter since it just has a single scart in and a single hdmi out.


Anyways I guess I won't bother with it then, the svideo out on the 2600 works fine and I have an svideo to hdmi converter, so I'll ignore the rgb out. Thanks for the help guys.

#7 ApolloBoy OFFLINE  



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Posted Tue Jan 9, 2018 1:07 AM

Either you have a thin cable with poor (or no) shielding or your SCART converter doesn't like the 2600RGB's output. I have an OSSC and it works great with the 2600RGB, no interference problems.

#8 iesposta ONLINE  


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Posted Tue Jan 9, 2018 2:09 AM

If it were processing stock video signal, snow in the output means the "green Chicklet-like" capacitor near the bottom left is going bad.

I had to replace one on a 4-switch I got in 2011 when I started retro gaming.


The RGB mod is unique in that it entirely recreates the signal from listening to the TIA chip and doesn't interfere with the original machine, as in if the RF box was still there you could hook it up to a TV on Channel 3 or 4. So it being a bad capacitor is a long shot, especially if the S-Video is great. (In my opinion).

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