hamburgerwalrus

Well, I fixed it, not sure exactly what did it but it was either dirty IC pins or dirty IC sockets. Pulled the TIA and RIOT, cleaned the sockets with Deoxit and a toothbrush, then I cleaned each IC pin with very fine grit sandpaper, and also Tarn-X. The new TIA did have some black spots on the pins, but the RIOT looked pretty clean. Working fine as of now, display is pretty clear considering I broke off a cap that can cause snowy output. I'll eventually replace that, and once I get a new soldering iron I'll probably just install the cap kit I bought. Now I can finally play Berserk, but I probably will need to clean these joysticks somehow as they aren't super responsive, could just be dirty boards in them.

Okay so found some more weird stuff. I tried all 10 games I own, every single one has vertical scrolling issues, except one. Q-Bert for whatever reason does not suffer from rolling video, but it is suffering from some other black magic. Also, Defender has the rolling video issue, but I noticed the direction the video rolls changes with the sound output of the game. I provided short clips of both games, and two others, below. I'm out of ideas. Why would Q-Bert be fine, well not fine but at least not rolling, while all others are? Why would the console output fine one second, and won't the next? Of course I can't recreate the fact that it worked perfectly normal on two occasions, but it definitely did.

All the soldering is from the factory, as far as I know, and I have checked continuity on all of the pins and they appeared to be passing a signal fine. After removing the TIA again and cleaning it well with a brush and some ISO alcohol, the video signal doesn't change at all when pressing on the chip as it did before. Now, the output is constantly the same thing. I'll grab another video to show exactly what I am seeing because it is a bit different from the one I posted before (before I cleaned and reseated the chip).

Hmm well I don't think that would be it, my color seems fine at least, it's just the constant scrolling that is the issue which is why I'm starting to think it's my TV. I'm not exactly privy on how analog TV's work but I know modern TV's don't have vertical/horizontal hold for analog signals, or at least mine doesn't, and this looks like a massive issue with vertical hold. The oddest part is the fact that it outputted fine on two occasions, but I can't recreate it even after trying it on another TV. I guess I can try the VCR again, I'm not sure if passing the signal through a VCR will apply some form of v-hold, but if so it may work. Or it could be this TIA chip not playing well with the PCB/motherboard in this Atari. I suppose I can message the seller on eBay and ask if they know if it should be compatible with a 2600A.

Okay yeah, I'm puzzled and beginning to think the 2600 doesn't like my TV. I've had it work perfectly fine twice, heck even the video signal was better quality than I expected. But once it works fine, I turn the system off, and turn it back on, and it's just constantly scrolling super fast. I think the new TIA works, because when it does work properly, it seems to be 100%, it just seems to only work sometimes and with no rhyme or reason. Though one thing I noticed is the startup sound to Pac Man seems really quick. Almost like when you play an old DOS game on a computer with a faster CPU, like the cycle rate is too quick for what the game was designed for. But I haven't gotten it working long enough to test how the audio sounds with other games. Going to try it on another TV, unfortunately this one is also not a CRT. I want to play some Berzerk damn it. (I know I can emulate, it's just not the same). I also read on another thread (I can't find it for the life of me) that after replacing the TIA you often times need to tune the Atari to get the signal proper. Anyone know what I am talking about? Maybe that could be an issue?

So I ordered a "new" TIA from an eBay seller who had really good feedback, seems they sell a lot of Atari products replacement parts. Says the chip was pulled from a working unit. I got it in the mail and inserted it, and well, it's still not working. When powering on all I got was a black screen with a tiny bit of snow. I noticed while pressing gently on the TIA chip while the unit was powered on, I would get video to display but it isn't a fixed image or nearly what you'd want to see. It's just a bunch of random colors and sometimes you can see the actual display of the game. I attached a video to show what I mean. I also noticed the two chips have different writings on the top. I'm not sure if this was pulled from a different model than mine, or just made in a different factory. I'm also not sure if all 2600 TIA chips are cross compatible or not. Below is an image of the new and old TIA, the new one being on the top. Considering the new chip seems to want to display the game when I press on it, I'm going to remove it and clean the pins off and also reclean the socket itself. Maybe it's just not making good contact. But if anyone has ideas, let me know. The chip was packaged very well and had no visibly bent pins. Edit: Well I got it working for about 2 minutes. After cleaning and reseating the new TIA, It was displaying Pac Man fine, I took the cart out to swap to another game, and now I'm having the same issue as above with super fast scrolling upwards. Maybe the cartridge slot is dirty? When pressing on the TIA now, there is no difference as there was when first inserting it.

I wish I had a test cart, I was looking through their flowcharts and always saw the mentioning of it. I guess it's not 100% necessary, but it would make troubleshooting a bit easier because you could directly compare with what the flowcharts say. Anyhow, I'm going to replace the TIA first. Even though it is more expensive. I just don't want to replace the RIOT and then find out my old one was perfectly fine, and then have to replace the TIA in the long run. Of course if worse comes to worst I'll have to replace both, but I'm keeping my fingers crossed.

I hate to keep re-upping this thread with random observations, but alas here I am. I read on another thread where someone said earlier 2600 games (such as Combat) are almost entirely TIA based and barely rely on RAM, so I decided to throw Combat in and see how it behaved. Same issues as before (scrolling screen, vertical bar in center, etc.), but I noticed a few things. The vertical line in the center of the screen is not just a graphical glitch, per se, I literally can not drive a tank through it. When switching to another game mode, such as the helicopter mode, I can fly around the entirety of the screen and do not see the vertical bar, but when firing I see absolutely no pixel showing the projectile exiting my tank/helicopter/whatever. None of the game modes seem to show any form of a "bullet" exiting the vehicle, but it does playback the sound of it firing. I also noticed that the opposing vehicles do not react at all to being hit by your bullets. I mean I can't see the bullets, only hear an indication that I am firing, but there is no reaction coming from other models to indicate that they have been hit. Also, on the tank mode, I think I remember there being a sound while moving the tank, but on this system there is none. I only hear the sound of the weapons firing and nothing else. Based on this alone, and with the reading I've done, this seems to say it's the TIA chip at fault. Putting money for replacement IC's aside, should I start with replacing that first?

Ahhh okay, wasn't sure if there was a method to test IC's with a multimeter or not. I guess it's off to ordering a new RIOT chip and keeping my fingers crossed that that is the only problematic IC there is. Will update with hopefully good news once I replace it.

Checked continuity of every pin on all three chips, every single pin checks out. So I guess that rules out the chip sockets being faulty? Should I still try and trace each pin of the chip to another pin on another chip? What would that rule out exactly? Damaged traces on the board itself? Also if one of the chips is just faulty and is what is causing this error, the continuity test wouldn't pick up on that right? Continuity simply just checks to see if a current can flow from point to point? If so, is there a way to check each chip to see which one might not be working 100%?

Just a small update. I can't find my multimeter but I have some free time tomorrow so I'll go out and buy one. Hopefully Home Depot has one for fairly cheap that can measure continuity. I don't think I need an expensive one, I rarely work with electronic components. I plan to test each pin of each chip to make sure the sockets aren't faulty, or something of that nature. I also received my recap kit today in the mail, but unfortunately the cap to replace the one I accidentally broke off has too short of leads to fit into that spot on the board. I've looked up ways to work around this (by essentially extending the leads), but might just be easier to find a cap with the same ratings and hopefully longer leads. From what I understand, the cap I broke off can cause grainy video, but it might be okay to do without it for the time being if I can fix all the other video problems. But either way I also need a new soldering iron since mine apparently doesn't want to work anymore, at least it doesn't want to get hot enough to desolder things (could be the soldering tip). But I plan to use the kit to replace most of the caps, voltage regulator, power jack, and RCA port. Hopefully the continuity test checks out and it's as simple as ordering a replacement chip or chips.

Well dang, I guess if it is just the RIOT chip being bad I'm in luck since that should be fairly cheap to replace. I just assumed graphical error = TIA, but I know nothing about how this stuff works. Welp as soon as I can source a multimeter somehow I suppose then I'll find out.

So the logic chip would be the TIA chip, correct? Still plan to test all chips before purchasing any replacements, but if the symptoms I'm showing can pinpoint things down a bit then that is always good. Glad I made this post here. Seems to be a lot of knowledgeable people on this board which is great. Glad to see so much passion for a system that is 40+ years old.

Haha, thanks, that makes sense. So one method basically follows a map of where the circuit (might be the wrong term) would travel to, and checks both ends, and one just tests to make sure that the socket itself is actually making good contact with the board. Forgive my lack of knowledge here, but the latter method seems much more doable with someone with as little experience with electronics as myself. If I can't find my multimeter, I'll try and see if a neighbor has one I can borrow or something, or I'll just have to purchase one. I took out the RIOT chip, the socket did seem a bit dirty underneath with what appeared to be white stuff. It cleaned off real easy and I reseated it, but no dice. Same issues as before. Testing each chips will be my next step and should at least help me pinpoint which chip(s) are producing these issues.

I'll try that next. Could you possibly explain the socket testing method you mentioned a little better? Or possibly have a link to a guide or video that shows this? It very well could be that the chips are fine, but maybe the socket itself, or solder connecting the socket to the board is bad. You had mentioned testing from the top of the pins to the top of the pins on another chip. So I'd place one probe of the multimeter on say a data pin on the RIOT chip, and then place the other probe on a pin on a completely different chip? Am I understanding that correctly? If so, does it matter which other pin I place the second probe on? I did try one other thing that made no difference. I ran the 2600 through a VCR thinking maybe it'd solve the scrolling issue or something. Still had the same issue, in fact I'd say the video quality was worse when doing this, but that could very well be the VCR's fault. So I'm thinking it's either a chip being bad, or as you said, a socket being bad, or just the connections to the sockets being bad. Going to take the riot chip out and clean out the socket a bit with some ISO alcohol and hope for the best. Should I bother doing this with the CPU at all? and thank you for the help thus far. I was weary about trying to fix this, but I am determined now. At the very least I may learn a thing or two.