4 switch 2600 snow unless I hold power switch upwards?

[+-^CrossBow^-]

13 hours ago, ChildOfCv said:

The TIA does handle the ball and missile graphics, and it also detects collisions of graphics objects.  So that does point towards bad TIA.

And I've had to replace more TIAs on 2600s and 7800s than any other chip in these old systems. I was only suggesting the RIOT based on the Atari service manual flowchart pointing to possible RIOT issues with corrupted graphics using the test cart.

 

 

[ChildOfCv]

Yeah, and you can still buy RIOT chips at a decent price too.  So without more informed failure analysis, that would be my first choice too.

[hamburgerwalrus]

1 hour ago, -^CrossBow^- said:

And I've had to replace more TIAs on 2600s and 7800s than any other chip in these old systems. I was only suggesting the RIOT based on the Atari service manual flowchart pointing to possible RIOT issues with corrupted graphics using the test cart.

 

 

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. 

[Bruce Tomlin]

My opinion is a bad TIA, because the glitch triggers collision detection with the background in more than one game, on the same column. And it would be bad on a background register bit the inside of the chip, not one of the pins.

 

EDIT: it seems the right pixel is missing on the pac-man ghosts too, so maybe it could be something wrong with the D0 line (or is it D7?), whether inside or outside the TIA. That would be pin 14 (34?).

Edited November 22, 2019 by Bruce Tomlin

[hamburgerwalrus]

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.

Edited December 2, 2019 by hamburgerwalrus

[hamburgerwalrus]

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?

Edited December 2, 2019 by hamburgerwalrus

[ChildOfCv]

They're talking about the color pot.  Each TIA has slightly different color shuffling speeds, so you have to adjust the potentiometer to get correct colors on screen.

[Tavi]

39 minutes ago, hamburgerwalrus said:

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?

This thread perhaps? It does mention that different brands/manufacturers of TIA chips can have strange effects on their 2600 (some similar to what you are describing; a bit of music and strange graphical artifacting).

 

 

[hamburgerwalrus]

23 minutes ago, ChildOfCv said:

They're talking about the color pot.  Each TIA has slightly different color shuffling speeds, so you have to adjust the potentiometer to get correct colors on screen.

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.

[ChildOfCv]

It sounds like the TIA itself may work.  But if things ever work better while pressing on a chip, that typically indicates intermittent connections.  Is the TIA socket new?  Are the solder pads on the bottom of the board new?

[hamburgerwalrus]

3 minutes ago, ChildOfCv said:

It sounds like the TIA itself may work.  But if things ever work better while pressing on a chip, that typically indicates intermittent connections.  Is the TIA socket new?  Are the solder pads on the bottom of the board new?

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). 

[hamburgerwalrus]

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. 

 

[emmanuelf]

Quote

All the soldering is from the factory

I think that you should redo the TIA socket soldering and checking that there is no track cut at the join between the track and the solder pad

[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. 

[emmanuelf]

?

[Trellot]

Might want to check back with that previous TIA chip to see whether or not you have two good chips now