rednakes1

The above method doesn't make sense, LOL, because you're pretty much taking away the Chroma by putting a huge resistor in between. The Chroma is the component that is actually introducing the red colour bleeding. One thing I noticed from looking at the schematics is that the Chroma is connected to the output of a 47pF capacitor that comes from Pin 9 of the TIA. If you decrease that capacitance, there is a slight noticeable decrease in bleeding. For example, I used a 68pF capacitor which I de-soldered from the RF circuit board that I had disconnected. If you connect it in series to the 47pF capacitor on the Atari, and then feed it to the Chroma output, you get a total of 22pF ( = 1 / ((1/47) + (1/68)) ). It doesn't make a huge difference but you will notice it if you look. If I can get a smaller cap then I can probably reduce the bleeding even more. EDIT: spelling

Just an update... For the colour bleeding issues in Jr Pacman and Pitfall where red bleeds to left, I have sort of fixed it by putting a 10K resistor at the Chroma, before it meets the Luma and Sync signals (this is in the resistor ladder diagram a few posts up). However, this causes the picture to become way less saturated, so there is still some adjusting to do.

I'm noticing on my screen that I get these diagonal lines moving on my screen. It was apparent after my composite mod (the one from coolretroprojects.com) but doesn't seem to show up in the RF connection. Could it be related to still having the RF circuit intact?

Yup I had looked for the service manual for my 13" CRT TV (Electrohome) but there doesn't appear to be any available on the Internet. Since it's a TV issue I'm not going to bother with it. Regarding the sound interference issue in Ms Pacman, I removed the audio wire from the board and reattached it from under the board this time, at the junction hole. But the problem still showed up. .

Seems like the distorted picture in the screenshot of Ms Pacman is due to my CRT TV. It shifts the image of far to the right and hence squishes it. Tried it on a 40" LCD and it is centered just fine, although it looks REALLY crappy due to that low resolution being stretched to HD.

So here's the next method I have tried, the one with the resistor ladder (DAC): It's the third diagram from this page: http://www.r3uk.com/index.php/tech-tips/39-cool-projects/71-atari-2600-composite-video-mods In this one, my only significant change was the removal of the capacitor next to the Chroma on the lower left of the schematic. It was causing white horizontal ghosting across the screen in specific cases; such as when it displays text on black background, or during a rescue descent in Cosmic Ark, or when the frog jumps in Frog Pond. I didn't have the exact parts: I used a 2N3904 transistor, the 4k4 resistor was changed to 4k7 (and used again in parallel for the 2k2 and 1k parts), and the 20 Ohm resistor was changed to 22, but those are very minor. ------- Here are the things I observed: Colour accuracy is amazing compared to all the other ones. Radar Lock now looks great, the enemies now look clear, the radar display is no longer smudged or wrong colour. Very pleasingly bright, even brighter than the same games played on the Atari Flashback 2; the other mods I tried were a tad dark However these things are still lingering just like in the other mods: Vertical line appearing down the center of the screen in rare cases during Ms Pacman, whenever the sound plays when she dies or devours a ghost (not as common as in the 2-resistor + 1 transistor mod). It might be a soldering issue with my audio wire so I will have to try re-soldering it. Colours are still bleeding - I wonder if the AV jack could be the issue here, if it's not the TIA Slight jailbars - this is probably something that cannot be fixed; it's not so bad but shows up more when the screen is bright Plus a new issue: In Ms. Pacman the maze now looks distorted/wavy on the right side of the screen (Why is it always this game causing problems!) I will likley end up with this mod, as long as I can figure out why Ms Pacman is causing the wavy right side issue. ---------- I'm attaching some screenshots to give you an idea what I see: Jr. Pacman: Colour bleeding on left of each wall and pellet Ms. Pacman - Right side shows that the maze is kind of curvy instead of straight Pitfall: Top image shows Atari 2600 colour bleeding on ladder and brick wall; bottom image shows the same game on Flashback 2 connected to same TV Radar Lock + Battlezone - beautiful colours.

Thank you, that's really generous of you! But I'd like to wrap this one up quick. I've been spending too much time on the breadboard, and I still have to solder up the components. I believe now that the TIA is not the source of colour bleed, as someone has told me he also tried swapping the chip out with a TIA from a good unit, and it did not fix it.

That wire (for audio) is at the junction of the resistor and capacitor, so it should be fine. EDIT: I could probably re-solder it to make sure that's not causing an issue. Concerning colour bleed, I suspect my TIA is the issue. Last night I tried the resistor ladder method (I will document this later), and while it gave the best possible picture to date, I still see the colour bleeding like in games like Pitfall near the ladder, and the walls in Jr. Pacman. On the other hand, games like Radar Lock now look stunning in comparison to before.

Cool, good to know it helps. I'll try the resistor ladder method in the coming days, once I get some more parts in. On a negative note, the Ms Pacman sound issue returned ;( It's so random and maybe it just doesn't happen to most Ataris.

I've managed to reduce some of the colour bleeding and a little of the jailbar effect to the Ben Heck mod I had been trying. It has also added a bit of colour vibrancy. See the attached image for the Before and After, it's from the menu of my Harmony Cartridge being displayed on my CRT TV. All I did was use a 1000pF capacitor which I took from the disconnected RF connector board, labeled "102" (I originally thought it was 0.1uF but it's actually 0.001 uF). I used it to bridge together the Video Out line to Ground. I did try 0.1uF instead but it caused the picture to get corrupted into white streaks on black background. This seems similar in implementation to the C215 (150pF?) capacitor on the motherboard that helps smoothen the picture in the 2-resistor + 1 transistor mod which I had originally tried in this thread. I believe that capacitor also goes to ground and then feeds into the Video Out line.

You mean the color pot that adjusts the tint after the mod is wired up? Yeah I've done that. I am using an Atari power supply; I did try a cheap one from eBay but I kept getting a horizontal rolling static.

Don't you need a specific minimum value for the resistor ladder? Also, could potentially a replacement TIA fix my bleeding issues?

Thanks for the tip. I am probably setting the values wrong or my TIA is not good. EDIT: Never mind, I noticed my Pin 5 was tied to 120 Ohms rather than 480. My mistake. The shades look better now.

So I spent some more time on this tonight. I'm not quitting! LOL This time I decided to try another method. I wanted to get a cleaner picture, so I had to get the video directly from the TIA rather than through a bunch of intermediate components like my other methods were doing. So to start, I went with a simple one - Ben Heck's original mod (Rev 1), which is linked here for the 4-switch 2600: http://benheck.com/classic/Question2.htm I used the following values, as I didn't have potentiometers or 22 Ohm resistors: TIA Pin 5 (Luma 1) connected to 480 Ohms* TIA Pin 7 (Luma 2) connected to 68 Ohms TIA Pin 8 (Luma 0) connected to 1000 Ohms *Actually i have no idea what Luma 1 does, because when I removed it from my circuit it had exactly no effect. I even increased/decreased the resistor values and there was no difference. I combined the above lines to Chroma (junction of R210/C210) and Sync (Pin 2) to get a composite signal to Video Out. No 5V source is required, so I'm assuming it won't work with all TVs if the signal is that weak. But it worked on my 13" CRT. Anyways the results: 1) Colours are still bleeding 2) Jailbars (vertical banding) are still showing up 3) Fixed the Ms. Pacman sound interference issue. Woohoo! I still want to fix #1 and #2. For the jailbars, probably I need a capacitor somewhere. Something like how C215 does for the other mods? I did try a 1uF capacitor between Video Out and Ground, but that made no difference. I think tomorrow I'll go to the electronics store and pick up some more components to try a more involved approach. I'll try the link @RevEng gave me above, and use the resistor ladder + transistor amplifier method. Or, if there's any other advice to fix up the mod that I just did, that would be appreciated!

Okay, so here's what I did just now on a breadboard, based on the schematic I linked 2 posts up. I hooked it up, and to my surprise, it actually showed an image. See the attachment for the version I made; I just tweaked the resistor values. (EDIT: I forgot to write that Audio also has a Ground on its jack, so don't forget to do that.) I used 120 Ohms instead of 100 Ohms, as it looked better, and I used 68 Ohms instead of 75 Ohms because that's all I had. Here are the changes I had to do on my 4-switch Rev 13 board: - Remove Q201 (or Q202) - this transistor will be reused for this mod - Remove R222 - will be reused for this mod - Remove RF circuit board and de-solder the pins from the holes - Remove R209 - Remove C215 - if you keep it on the board you won't get a noticeable jailbar effect, but ghosting will be very bad Some observations: 1) Colours are very vibrant with these resistor values. Looks great. If I remove either of the 120 or 68 Ohm resistors (or reduce the resistor value), the colours will come out very dull. 2) In Ms Pacman, the audio distortion effect (vertical line down the middle) still happens, but only once in a while. It's very random, in some sessions it shows up when you die, and in other sessions it doesn't show up at all. I tried moving wires around on the breadboard so that there wouldn't be any touching, but it was again still randomly happening. 3) The jailbar effect is caused by removing C215, but I had to do it, because otherwise the colours go dull and you see *major* ghosting: some colours such as pink or white leave a long ugly streak to the right of the graphic. But otherwise, with C215 the image would have looked smoother and with not much jailbars. So there's the trade-off. Currently the images look a bit pixelly; you can see the dots. 4) There's still bleeding of colours as before. Quick test: Just start up Adventure and look at the number "1". It has a shadow in a different colour, when it shouldn't have any shadow. Currently I'm not entirely happy with this version as the images are not as clear due to removal of C215. But it's more colourful, and the Ms Pacman issue is not frequent. Other people may have better luck with their Atari. Plus you can save money if you decide to use it. I wish I could add some samples of the games, but I have to shut down and go to bed.

Got it today from the local Chapters (Canada), it was 52.99 but today if you spent more than $50 you get 25% off. I'm loving the book, it's very thorough and it's a good read.. Oh, and the pictures are great too My kids got a kick out of the different concept drawings for Pac-man.

No this is Ben Heck's mod for the 4-switch: http://benheck.com/classic/Question2.htm

Thanks, it did give me some insight but it's a little too involved as I don't have all the parts on me (high resistor values and pots). It's also for PAL but mine is NTSC, so I don't know if things will be different. However, I saw this thread as well: http://assemblergames.com/l/threads/composite-atari-2600.48162/page-2 See the last post with the 15K resistor from R222 as well as the transistor at Q202 being reused. I'm actually going to prototype it on a breadboard and test it out when I have time. I took off R222 from my Atari and it had no effect on the current issue, so I will reuse it. There is also a 100 Ohm resistor on the RF connector board that can be reused for this.

The lowest cap I have is 1uF, which I reused from the RF connector board. I used it to bridge the 5V and Ground going into the video mod board, but it didn't seem to have any effect. I haven't tried any other TVs. I actually tried connecting to one of my LCDs but somehow it didn't detect the AV connection. For now it's on my CRT TV which hasn't been giving problems on other AV devices (Colecovision, Atari FB2, PS2). I haven't been up to speed on Luma/Chroma, how could I resolve the potential issue you mentioned?

Yeah I could try that but I don't want to throw more money at this little project right now. I want to see if I can get anything out of the one I bought, and try to understand what's going wrong so that another mod in the future doesn't show the same symptoms. Thanks for your input though.

No I didn't use a capacitor. What amount should I use and where should I put it? I'm attaching a schematic of the AV mod, which I got from another post.

Okay so here's what I've done in the last little while. No improvements yet but I thought I'd share: The colour bleed is worse than I thought; I guess when I compare it to my Colecovision Expansion Module 1 it is more obvious. Text is not sharp, graphics are a bit blurry too as a result. - removing C215 increases the jailbar effect noticeably (this cap is one of the last components that feeds into the Video Out line) - Removed the big ugly RF box finally - no effect as expected, but just wanted to make sure - Colour bleed makes games like Radar Lock look really bad, blurry and almost unplayable (compared to how it looks on the Flashback 2, it makes me sad!) - Regarding the sound interference issue in Ms Pacman, disconnecting the wire for Audio Out from the main board still doesn't prevent the vertical line when sound is supposed to be played. Tested on both Harmony Cartridge and original cartridge, same issue. - Added a 75 Ohm resistor to bridge Video Out to Ground, but it made no difference to colours or brightness or the Ms Pacman issue (it's recommended for impedance matching, and used in some schematics) I wonder if there's anything else I should look at, such as the three Luma lines from the TIA?

Thanks for the tip, yeah I eventually removed the tape and it didn't do any harm. One thing I noticed with the video quality is that you may see a row of white dots on the left side of the screen. My 2600 Jr. also has the same effect so I guess it's a symptom of the extra saturation.

Possibly the reason is the amount of volume coming out of the Atari, which is causing interference in the game? I am suspecting this could be the reason, because today I tried my Colecovision Expansion Module 1 with my Atari games, and then compared the same games on the Atari 2600 4-Switch. The Coleco had no issue issue with Ms. Pacman, and the volume in comparison was noticeably louder on the Atari 2600. Possibly the amount of audio amplification is causing interference somehow in Ms. Pacman. So my question is, how do we adjust the audio amplification? I'm guessing R206 could be replaced with a bigger resistor?? No idea... As an aside, my Coleco Expansion Module 1 looks great after the A/V mod on the Colecovision. Sharper than the video with the Atari mod, which looks a bit too soft. However the Coleco also shows the colour bleed with Jr. Pacman, so maybe it's not too big a deal then.

Hmm I didn't notice the problem when it was unmodded (I play a lot of Ms Pacman), but perhaps it was masked by the RF static. You may be right and it may be one of the original components not acting well..