Atari 2600 Video-Out modification

[church]

If you still have any left I as well would be interested.

[CPUWIZ]

The mod works fine on a PAL 2600, I will post some pics of it tommorow. A buddy is bringing me a new PAL case for the damaged one I traded with that guy from the UK (sheesh - bubble mailer) tonight.

 

Once I have it all re-assembled, I have a pre-modded PAL 2600 Jr. unit for sale (or trade) if anyone is interested.

 

Later

-R

[cwilkson]

Hope this isn't like the 2600 AV add-on board that was on display for the 2001 CGE then just kind of disappeared.

 

That one was mine. Sorry it disappeared, but there were circuits that

were very layout sensitive...I had to tweak it to get it to work for the

show. Since then, I have been working on it, trying to get it ready for

prime time. The circuits are designed...I just finished them this

weekend. Now I just have to make a beta proto and a pcb proto.

 

Attached is a screenshot of the breadboard proto in action.

Tell me what you think!

 

-Chris

[Thomas Jentzsch]

Great quality!

 

Nearly looks like a screenshot taken directly from an emulator.

 

BTW: It's hard to decide which errors are comming from JPG-Compression. Could you post a loss-less compressed version, please?

[CPUWIZ]

That does look almost fake, did you use a tripod to take the picture or did you pipe the video-out into a capture card ? I have never been able to take a screenshot with a digital camera like that.

[cwilkson]

This is a direct S-video capture. I'm using an ATI AIW Radeon 7500

to capture with. Regarding compression formats...is LZW loss-less?

If not, I can post it uncompressed in .tif or .bmp format.

 

EDIT: It's not letting me post .bmp files, and it doesn't recognize the

.tif files. I'll put them on my website later this week. Or I can email

them to you.

 

-Chris

[Paul Slocum]

Attached is a screenshot of the breadboard proto in action.

Tell me what you think!

 

Wow Chris! That looks amazing!

 

.PNG is lossless.

 

-paul

[+Nathan Strum]

The circuits are designed...I just finished them this

weekend.  Now I just have to make a beta proto and a pcb proto.

 

That screen capture looks pretty amazing.

 

I guess I should introduce myself or something. I'm new here. (Well, "new" being a subjective term... I've been regularly visiting AtariAge.com for quite a long time, but just haven't gotten around to posting until now.) I'm a long-term, die-hard, old-school gamer, Battlezone is my favorite game, yadda yadda yadda. I run MacMAME.net, and moderate The MacMAME Message Board. Stop by and visit anytime.

 

So, that's out of the way.

 

I'm wondering which approach you're taking to the circuitry? The "build an amplifier of some sort" method, or the "squish all of the luma together" method? I've been building and testing three of the mods from the FAQ (Chris Cracknell's, Ben Heckendorn's, and the one which uses a CD4050 hex buffer), and I'm working on the "video driver" one next. (These are all tested on a six-switch 2600.)

 

At some point I hope to put up a comparison on the web between the different methods, basically to show people how well each one works. The CD4050 one is far and away the best of the bunch so far - although it's not 100% perfect. (The others are too far off to really be usable, in my opinion.)

 

What I've been using as a standard, is the Color Bar Generator cart, a copy of which I had made by Hozer Video Games. This gives a consistent indication of colors, gray levels, and also has a chroma adjustment screen (on the title screen) which lets you tweak the chroma of any 2600 using the big pot on the main board. By comparing the RF out of a tweaked 2600 to that of the various mods, I've been able to determine how accurate (or not) they are. I'm taking screen captures as I go along, too, so people can see for themselves what the differences are.

 

The ultimate goal was to put together a "how-to" guide for building a mod. However, if you're working on a solution that will ultimately be available to the rest of us, I may just bag the whole project. Or add yours to the comparisons.

 

Anyway, all that is a way of saying I'd really like to see what solution you've come up with when you get it ready for primetime. Is it based on one of the existing designs, or is it home-grown? And you mentioned S-Video. Is the mod itself S-Video, or are you using a composite to S-Video adapter?

 

Sorry for all the questions. They've been building up for awhile.

[Thomas Jentzsch]

EDIT:  It's not letting me post .bmp files, and it doesn't recognize the

.tif files.  I'll put them on my website later this week.  Or I can email

them to you.

Try GIF or PNG.

[cwilkson]

Thanks everyone. It's good to see that other people like the quality!

I've been staring at this thing for soooo long now, that I'm afraid of my eyes playing tricks on me. Here's a PNG image. It's a completely new capture, BTW...I already deleted the other one.

 

Nathan, I'm using a bit of everything. There are voltage amplifiers, current mode circuits, rf (of course)...a lot of analog nightmares. My general approach is to take what's available from the TIA itself and then create actual video signals...not just munge everything together until it looks good on a TV monitor. It has a native s-video output, so no converter is needed. Oh...it's home grown too. The CD4050 version is one of the better ones. There are a few variations of that one even. It's ridiculous to just tie the TIA lines together with a capacitor and a few resistors and expect that to drive a 75 ohm load at 1V. You need to buffer the signal. The 4050 helps get a good signal source, but then you still need an output buffer of some type.

 

I like your approach of building each mod and comparing/contrasting it with all the others. My mod will be available in kit form and pre-assembled. I'll sell it directly, and probably through the AtariAge store. Maybe elsewhere. It will come with controls for contrast, brightness, and color saturation. Outputs are composite video or s-video, and stereo audio. Once it's available, I'd love to see it listed on your web page.

 

I have a custom test program I use to generate video test patterns. Similar functionality to Color Bar Generator. I use an oscilloscope to spec the waveforms, and my monitor to get the visual cues I need to pick up any problems. One of the hardest things is getting the contrast, brightness, and color saturation controls to work right. And getting clean power is never easy in a digital system. So I may have to build a custom

powersupply on the board. Yuck.

 

That's all for now. Thanks again for the feedback everyone!

 

-Chris

[Rob Mitchell]

Richard Hutchinson and I are making PCBs of the CD4050 circuit with built-in stereo for modifying consoles ..

 

Rob Mitchell, Atlanta, GA

[jsoper]

I've modded a few 2600s and 7800s and I like to use the 4050 mod but without a 4050 (the transistor is enough of a buffer itself). I also solder the luma and sync components down on the motherboard and join them there so you only need one wire to the transistor board instead of four.

 

The FAQ says tie chroma and luma together for composite but I get a better image by using one transistor for both the chroma and luma. My portable 2600 uses this circuit and it's looking good.

John

[+Nathan Strum]

Nathan,  I'm using a bit of everything.  There are voltage amplifiers, current mode circuits, rf (of course)...a lot of analog nightmares.  My general approach is to take what's available from the TIA itself and then create actual video signals...not just munge everything together until it looks good on a TV monitor.

 

I have a custom test program I use to generate video test patterns.  Similar functionality to Color Bar Generator.  I use an oscilloscope to spec the waveforms, and my monitor to get the visual cues I need to pick up any problems.

 

That sounds like a great, methodical approach. I've got a Magni waveform monitor/vector scope that I'm going to compare the different mods through as well. (Although the munged video mods are so shakey, I'm going to have to run them through a TBC just to get a stable enough signal to read.) What sort of NTSC monitor are you using to view the results? I'm using a Sony PVM-14M2U. It's a bit fussy about what video you throw at it, so it's probably not as forgiving as consumer TVs would be with the simple mods.

 

It sounds like there are quite a few more flavors of the mods than are listed in the FAQ. I did some searching, but usually just came up with stuff for the 400/800.

 

I like your approach of building each mod and comparing/contrasting it with all the others.  My mod will be available in kit form and pre-assembled.  I'll sell it directly, and probably through the AtariAge store.  Maybe elsewhere.  It will come with controls for contrast, brightness, and color saturation.  Outputs are composite video or s-video, and stereo audio.  Once it's available, I'd love to see it listed on your web page.

 

I'd be more than happy to include it! I'll make an effort to include whatever mods are publicly available or published on the web. If you're making a list of pre-orders, put me down for one. It sounds like a really complete solution. The pre-assemled part of it will be most welcomed to the soldering-challenged. (Personally, I love the smell of molten solder... but then I'm probably partially brain-damaged from it, too.)

 

I'd also love to see the PCB for the CD4050 that Rob Mitchell mentioned. Hand wiring it was a pain, and not for the faint-of-heart.

[Thomas Jentzsch]

Here's a PNG image

Thanks! The new image looks even better!

[stinky817]

My mod will be available in kit form and pre-assembled.  I'll sell it directly, and probably through the AtariAge store.  Maybe elsewhere.  It will come with controls for contrast, brightness, and color saturation.  Outputs are composite video or s-video, and stereo audio.

that sounds great, sign me up for one (that's if you're taking pre-orders ) i dont care how hard it is, just include directions on what i need to do, and i'll do it

 

(Personally, I love the smell of molten solder... but then I'm probably partially brain-damaged from it, too.)

... i dont think i've found anybody that doesn't love the smell of molten solder... i went to a school for EET, and all the first semester classes smelled like that, one reason i LOVED going there

[+Nathan Strum]

I'd like to get some feedback on what games people would like to see tested under the various video mods. The Color Bar Generator cart, while useful, is hardly exciting (and certainly not something most people dig out to play every day).

 

I've been using Crystal Castles (the blue dots on the first level's playfield are hard to reproduce), and David's Midnight Magic (lots of color bleeding in the bumpers, the thin lines tend to break down, plus there are five mini "color bars" across the top of the playfield for checking the color).

 

So, if any of you have some suggestions of games you'd like to see tested (with frame captures of the end results), please post 'em here. A list of the games I have is here. Anything not on that list, I can't test. (Edit: Whoops... forgot about the CD with all of the Supercharger games on it. So I have the rest of those, too.)

 

Although if someone wanted to give me a copy of Crazy Climber... I certainly wouldn't object to it.

 

I'd like to keep the list fairly short - 10 games or so.

[church]

Well since I would really like to get one of these for my own atari project I'm going to suggest demon attack to help speed things up. The trippy, quick colour changes might be a good to test the rca out on.

[cwilkson]

I've been using Pitfall 2 lately. It's hard to get bright yellows and color

fields right and Pitfall 2 lets you test both. The water and ledges give you

good blue and gold fields all across the screen, and the trees give you

green. And the red save point crosses let you check for red color bleeding.

 

-Chris

[jsoper]

Chris is right, it's also good for checking stereo sound. I've actually gotten sick of the PITFALL2 game because I've used it for so many hours of lab work.

[+Nathan Strum]

Chris is right, it's also good for checking stereo sound.  I've actually gotten sick of the PITFALL2 game because I've used it for so many hours of lab work.

 

Cool. Pitfall 2 has enough screens for variety, so that'll actually make up for several games.

 

I'll check Demon Attack, too, although I'm not as certain about how easy it will be to pick out colors and artifacts, given that there aren't a lot of broad expanses of colors.

 

Any more suggestions? I'll probably go through my whole list (in Stella) this weekend to look for more candidates. With any luck, I can get a basic web page put together in the next couple of weeks (if not - it'll have to wait until January).

 

Lastly - jsoper, do you have a diagram of the circuit you built available online somewhere? I'd like to try that one out as well.

[jsoper]

Actually my mod is just the chroma/luma 4050 mod from the FAQ without the 4050. I don't think it's needed because the transistor acts as a buffer and the 2600 only sees a 750 ohm (or so) load instead of a standard 75 ohm TV load (which is a shortcoming of all non-transistor mods).

 

If people really want a 4050, the 6-switchers and juniors (not 4-switchers) already use them and you can tap the signals from their output pins.

 

I'd recommend keeping the signal lengths as short as possible and disabling the audio mixer transistor, the FAQ explains it somewhere. The beauty about chroma/luma (s-video) is that the highest frequency content is about 3mhz (luma) and 4mhz (chroma), again rough numbers. RF is in the tens of mhz and the frequencies all interact. S-video will outperform RF even with worse cables. And your comparison experiments might only show the differences in workmanship instead of circuit performance, or maybe not. That's why I'm suspicious about the 4050, the extra wiring may hurt more than help.

 

For composite, differences in circuits should show up more. On a 2600, I still think the best way is to use the chroma/luma circuit but send the chroma to the luma transistor instead of a separate transistor. All resistor values stay the same of course.

John

[+Nathan Strum]

Thanks for the feedback/tips John!

 

Certainly, the way I'm wiring stuff up, there could be problems due to wire length. (I've set it up with a terminal block so I can switch mods in and out without resoldering all the time.) However, the lengths should be consistent between all of the mods, so they'd all be affected in the same way.

 

I wonder though - if that has something to do with the one issue I have with the 4050 mod: green text. (Actually, any thin, vertical white lines turn green, such as those on the color bar cart. But it doesn't affect large areas of white.)

 

Anyway, I'll check out the 4050 mod sans the 4050, and see what I get. For adding the Chroma to the Luma's transistor, do you go straight from the Chroma connection off the TIA, or do you take it after the 6.8k resistor in the FAQ's diagram?

 

Also, the FAQ only mentions disabling the audio mixer on a 7800, not on a 2600 (at least as far as I could tell).

 

I suppose I'm probably not the ideal person to actually do a comparison project, since my technical knowledge of video isn't really all it should be, so while I can follow and build circuit diagrams, I can't really determine how to tweak something that isn't right. But I'd build the mods for my own curiosity anyway - so why not?

[EricBall]

I created Skeleton with stereo sound in mind, so it should make a good test base for that.

[Rob Mitchell]

I created Skeleton with stereo sound in mind, so it should make a good test base for that.

 

Great stereo BTW. SKeleton is great in stereo!

 

Any of the early games use L/R sound: Combat, Air-Sea, Indy 500 etc. Best L/R sound is the Synthcart.

 

Rob Mitchell, Atlanta, GA

[EricBall]

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.