Atari 2600 Video-Out modification

[Inky]

Yep, Windy City, the only place where I have seen someone's coffee freeze right in front of me.  

 

I bet they are all different just like the NTSC ones, I am only really concerned with the 4 switch, 6 switch and the Jr. !

 

Actually, the term Windy City was placed upon Chicago by a newspaper editor back in the late 1800's when Chicago and New York were both trying to get the World's fairr. THe eidtor of the New York paper said 'Ignore the boastful claims of that 'Windy City'" Some think it rfers to the politicians here as well. They are very windy indeed.

 

And I'd be interested in the kit for both 5200 and 7800

[Rob Mitchell]

The TIA only had two audio channels, so it's hard not to make a stereo game.  However, Skeleton was programmed with stereo in mind; and I doubt that there are any other games which were.

 

I think you are right about this .. Skeleton is the only true Stereo game .. The others previously mentioned do use the L & R audio channels .. but that is not an integral part of the gameplay.

 

Rob Mitchell, Atlanta, GA

[+Nathan Strum]

Well, that took a little while. But I've got a page up comparing (some of) the video-out mods for the 2600.

 

Please look it over, and let me know what you think. I'd be more than happy to add more later. (And if anyone has a guess as to why the video driver mod may not have worked, or how to troubleshoot it, please let me know.)

 

Thanks!

 

- Nathan

[Thomas Jentzsch]

Great job!

 

There is (at least in PAL consoles) a pre-set potentiometer that changes the color balance. Did you try tweaking that too?

 

Now I'm looking forward to the ultimate mod.

[+Nathan Strum]

There is (at least in PAL consoles) a pre-set potentiometer that changes the color balance. Did you try tweaking that too?

 

On my 2600, there was only the one large pot, and I tweaked that using the Color Bar cart - basing those adjustments strictly on the instructions for that cart (thanks to whoever dug these up, and to AtariAge for making them available):

 

The color phase angles are generated by delaying the color signal until the desired phase angle is selected. An adjustment potentiometer is placed on the VCS console circuit board to adjust the 360 degree delay so that it is the same as 0 degrees. Although we do not recommend that you void any warranty on your game console, the potentiometer (the only one) can be adjusted so that the top half of the colored box is as close to the same color as the bottom half. The color generation circuits can then correctly produce colors from 0 to 360 degrees.

 

So doing that, I figured that would give the best idea of which video mod was interpreting the color signals most accurately, rather than adjusting the pot until the colors fell into line elsewhere (on the color bar screen, for instance). That way, I'm testing how each mod works, rather than trying to compensate for each mod until it works. (The exception being Ben's mod, since his uses two pots for adjustment of the signals. So there was a lot of back-and-forth tweaking until I could get the title screen on the color bar cart to look right and get the color bars and grayscale screens to look as close-to-correct as possible.) I think (hope) that this is a fairly objective approach. Of course, I'm always open to suggestions.

[Rob Mitchell]

Norman:

 

I'm surprised that you did not get the CD4050 mod with separate Lumina Chroma (S-video) to work. Works great for me .. with the Commodore Monitors that accept the separate L/C signal.

 

Also you should include a little blurb about the stereo mod: Separating TIA pins 12 and 13 to separate outputs.

 

Rob Mitchell, Atlanta, GA

[+Nathan Strum]

I'm surprised that you did not get the CD4050 mod with separate Lumina Chroma (S-video) to work.  Works great for me .. with the Commodore Monitors that accept the separate L/C signal.

 

Well... rats. After reading your post, I just went back and reconnected everything, and for some reason, now it works. (I must've missed a wire the first time.)

 

So, it looks like I'm in for another round of tests. But, that's a good thing. The picture is considerably cleaner.

 

Also you should include a little blurb about the stereo mod:  Separating TIA pins 12 and 13 to separate outputs.

 

I didn't know about that one. I made a note of it. (A quick check of the circuit board later...) But, where do you separate them out? Do you have to cut a trace on the circuit board? Also... which pin is considered left, and which is right?

 

(And who's this "Norman" guy?)

 

I may have to not use so many screen captures, or I'm going to run out of disk space in a hurry. Any suggestions on what can go?

 

I was thinking of cutting:

 

Midnight Magic (the "bumpers lit" one) - it's 99% redundant

Pitfall (starting screen) - most elements are redundant

Tac/Scan (level 2) - there are enough black-background screenshots

Centipede (level 1) - blue and red are both present in level 2

 

And I may drop the 7800 switchbox set entirely (but keep the RF adapter set).

[Rob Mitchell]

Well... rats ... .

 

Rats are good!

 

I didn't know about that one. I made a note of it. (A quick check of the circuit board later...) But, where do you separate them out? Do you have to cut a trace on the circuit board? Also... which pin is considered left, and which is right?.

 

On the 4 switch, there is a tracing that shorts the two pins immediately right there on top of the board. I think this would be difficult to cut to separate. But the TIA is socketed so it is easy to remove, and then bend out pins 12 and 13 and then go from there. You need to put a piece of electrical tape over the pin connections to insulate from the RF aluminum shield.

 

Recently I looked at my Jr .. and I could not see the same wiring for 12 and 13 .. so I don't know that the stereo mod would work for that one. Because I did my mods in 1998, I don't remember which is right and which is left. Just throw in a Combat and check.

 

>>(And who's this "Norman" guy?) <<

 

Uh .. gh .. Hi Nathan ..

 

Rob Mitchell, Atlanta, GA

[+Nathan Strum]

But the TIA is socketed so it is easy to remove, and then bend out pins 12 and 13 and then go from there.  You need to put a piece of electrical tape over the pin connections to insulate from the RF aluminum shield

 

Eek. Pin-bending the TIA?

 

I wonder if you could just stack a second socket in the first one, and bend the pins on that instead? That way, if you wanted to put it back the way it was, you could do so without risking snapping the TIA's pins off.

[Rob Mitchell]

I wonder if you could just stack a second socket in the first one, and bend the pins on that instead? That way, if you wanted to put it back the way it was, you could do so without risking snapping the TIA's pins off.

 

Of course! That's a better solution!

 

Rob Mitchell

[+Nathan Strum]

Okay. I've updated the page with the S-Video tests for the CD4050 (and the non-CD4050 version). (S-Video wouldn't work with Ben's mod.)

 

I ended up only needing to dump the second Midnight Magic image from all of the tests, and the entire 7800 switchbox test results (the 7800 RF adapter results are still there) to gain enough space for the new results.

 

The differences are rather dramatic... I was so surprised at how good the S-Video actually looked, I nearly made the mod permanent right there. Compare one of the switchbox pics to one of the S-Video pics for a good chuckle.

 

There are still some odd little artifacts, which I'm not sure if they are due to the mod, or are just part of how the 2600 does its business. The noticable ones are red edges on some graphics (the ladders in Pitfall II, the blue crystals in Crystal castles) and blue edges along the table in Midnight Magic. Tac/Scan looks much better, but has rolling hum bars all of the time, which is particularly noticable in the first (blue) wave. I suppose that could just be an oddity of the cart. Anyway, if someone can create a mod that looks good on Midnight Magic and Tac/Scan, they'll really have something.

 

The other thing I noticed (but didn't note on the page yet) is that on the CD4050 mod, the audio will generate some noise on the picture. It varies depending on the sounds being played. Some have no effect at all. None of the noise was really significant, and far less than you get even with composite video. I didn't disable anything on the circuit board, so perhaps that could account for it. Not hooking the audio up to the mod at all resulted in no picture noise, although there wasn't any sound either (since RF wasn't hooked up). For the new screenshots, I left the audio off for best picture clarity.

[Rob Mitchell]

The differences are rather dramatic... I was so surprised at how good the S-Video actually looked, I nearly made the mod permanent right there.

 

Yes .. very nice!! The colors are vibrant .. images are sharp .. It makes colorful games like SCSIcide shine

 

And with stereo out .. the sound is so clean .. without any buzz. Go ahead and do that mod!

 

Rob Mitchell, Atlanta, GA

[+Mitch]

I remember a while back someone posted that the CD4050 amp was too strong for their 2600 and going without it was to weak, so they used an amp that was not quite as strong as the CD4050 and it worked better. Unfortunatly, he never mentioned the chip number. Does anyone have any ideas? It might be worth testing out. Especially if you socketed your CD4050.

 

Mitch

http://atari7800.atari.org

[+Nathan Strum]

I remember a while back someone posted that the CD4050 amp was too strong for their 2600 and going without it was to weak, so they used an amp that was not quite as strong as the CD4050 and it worked better. Unfortunatly, he never mentioned the chip number. Does anyone have any ideas? It might be worth testing out. Especially if you socketed your CD4050.

 

I'll be happy to run tests, if someone can get the part number.

 

However, I didn't think the CD4050 was too strong. It seemed very close in value/intensity to the RF output (which is sort of a reference), and generated a very nice grayscale ramp on the Color Bar cart. The 2600 games just have a tendency to blow out chroma values, especially those intense solid blues such as the water in Pitfall II, and the first castle in Crystal Castles (as well as the 2x table in Midnight Magic, but I didn't include that as part of the tests). You just see more clearly how blown out that video is when the mod is hooked up, and some TVs don't handle it too well - especially if they aren't calibrated properly. After all... NTSC stands for "Never Twice the Same Colors".

 

And with stereo out .. the sound is so clean .. without any buzz.  Go ahead and do that mod!

 

Well, I'm not going to make a permanent mod until I have a chance to test out cwilkson's upcoming one, and whatever other ones (PCBs, other variations, etc.) come to my attention over the next couple of months. I'd like to make sure as much gets covered as I can so it's a fairly complete overview of what's out there. Once I make my own mod, there's not going to be much incentive for me to keep testing stuff out.

[Rob Mitchell]

Richard Hutchinson just posted a pic of the CD4050 PCB video stereo audio circuit board here:

 

http://www.atariage.com/forums/viewtopic.php?t=17748

 

Awesome!

 

Rob Mitchell, Atlanta, GA

[jsoper]

someone posted that the CD4050 amp was too strong

I don't understand how a 4050 could be too strong when it's only a digital buffer. Output is 0v when input less then 2.5v. Ouput is 5v when input greater than 2.5v.

 

the audio will generate some noise on the picture

You can get rid of audio noise by cutting the base lead of the Q201 transistor. Schematics here:

http://www.atariage.com/2600/archives/sche..._2600A_Low.html

but you must then tap out audio directly, mono or stereo, because it won't be in the RF.

John

[+Nathan Strum]

You can get rid of audio noise by cutting the base lead of the Q201 transistor.  Schematics here:

http://www.atariage.com/2600/archives/sche..._2600A_Low.html

but you must then tap out audio directly, mono or stereo, because it won't be in the RF.

John

 

Thanks! Seems to me I'd read something about that, but didn't know the specifics, plus at the time I ran the tests, I didn't want to cut (or desolder) anything from the 2600. But leaving the audio mod disconnected gave me a noiseless picture for the video capture, which is what I needed at the time. When I make a permanent mod, I'll use direct audio and desolder the Q201 base lead, and just lift it out of the way.

 

By the way, I appreciate all of the helpful comments here! This has been a good experience. Not all forums are quite as welcoming to new people.

[tim.]

I thought i'd post my video mod

http://members.optushome.com.au/worthair/atarivi2.pcx

 

it works differently form most of the others ive seen in that it doesnt pick signals streight off the open collector outputs of the tia but rather takes the video signal (which is composite video) just before it gets into the rf modulator and buffers it so it can drive a 75 ohm load like a tv/monitor

 

it does require a few modifications to the atari itself though. The audio mixing oscillator needs to be disabled (remove R56) and the rf modulator needs to be taken out of the circuit since it pulls the video signal's amplitude down. You will have to work out how to do that on your model. (on the atari 2600jr it can be done by removing R17 and C33 from inside the modulator since its part of the circuit board)

 

it gives a great picture and should work well both PAL and NTSC systems since the circuit is just an amplifier.

 

to locate the components mentioned refer to

http://www.atariage.com/2600/archives/sche..._Junior_PAL.gif

[Nukey Shay]

Greetings, O tim. the enchanter... j/k

 

You can post images by using these tags...

[img] and [/img] instead of using url.

[stinky817]

I thought i'd post my video mod  

http://members.optushome.com.au/worthair/atarivi2.pcx

 

too bad i cant see it i tried copy/pasting it into IE... still no luck, download... no dice... what can i use to open it?

[CPUWIZ]

It's probably because of the PCX fileformat, here is a JPG of it:

 

[Rob Mitchell]

It's probably because of the PCX fileformat, here is a JPG of it ...

 

How do you convert from one format to another? I have *.tif images which I cannot display on AA.

 

Rob Mitchell, Atlanta, GA

[CPUWIZ]

Load it into Photoshop and do a "Save As". If you don't have it you can send me the TIF's and I'll do it for you.

[+Mitch]

I don't understand how a 4050 could be too strong when it's only a digital buffer.  Output is 0v when input less then 2.5v.  Ouput is 5v when input greater than 2.5v.

 

I don't know, here's the thread where it was mentioned. It's the last post in the thread.

 

Mitch

http://atari7800.atari.org

[Rob Mitchell]

Load it into Photoshop and do a "Save As". If you don't have it you can send me the TIF's and I'll do it for you.

 

Thanks .. I'm at work right now .. Later I will send a few key pic.TIF images for you to convert and post on AA. Pics of my custom 2600 and the Starplex 5 button Controllers.

 

Rob Mitchell, Atlanta, Ga