7800 plays 2600 games, but video is garbled. 7800 games work great.

[CFVG]

I've got a 7800 that was giving me audio and color problems at first with 7800 games. I was able to work it out with some cleaning and re-flowing of the color adjustment potentiometers, as well as giving the game slot a good clean and adjustment. It plays 7800 games with great color and sound.

 

Now I'm having issues with 2600 games. They start up, and display on-screen, even allowing me to start a game and play. The problem is some vertical lines on the screen and a garbled mess. It's not just the video signal though, the lines and walls that are displayed affect gameplay as well.

 

What I have done:

1. re-flowed solder points for the color adjustment potentiometers
2. marked the original setting and twisted the color adjustment potentiometers to break up any corrosion.
3. adjusted the RF modulator pot
4. cleaned the cart slot pins and bent them out a hair for better contact

I also tried adjusting the lower 2600 color wheel with no progress (pot will change the color but not alleviate problem)

 

 

Here are some pics of the problem I'm having. Any input on what to try would be greatly appreciated!

 

Barnstorming

 

Pac-Man

 

[Rybags]

Looks like a problem within TIA itself re logic for Playfield/object display. Although Maria generates the clocking for the CPU and TIA so it can't be ruled out totally. The RIOT contains system RAM for 2600 mode, if that's faulty then it could cause glitching too.

[CFVG]

Looks like a problem within TIA itself re logic for Playfield/object display. Although Maria generates the clocking for the CPU and TIA so it can't be ruled out totally. The RIOT contains system RAM for 2600 mode, if that's faulty then it could cause glitching too.

 

I did some research on the info you gave me. It would make sense for the TIA chip to be defective, since it seems to control a lot for the 2600 side of things. I didn't happen to notice if it's socketed in the 7800 pro system I have when it was apart though. I guess the next question is where do I get one, or am I even able to?

 

I can't find any info on where the RIOT chip may look like or where it is, but I think the better option would be trying the TIA chip if I can get my hands on one

 

UPDATE

 

Took apart the 7800 again to check out the TIA chip to see if it was socketed. Unfortunately, it wasn't. I called up a shop in CA that seemed to carry them and he was awesome enough to give me some more info on the board. For the sake of sharing the info and future people with similar problem, here are the chips on the board.

 

Edited February 20, 2014 by CFVG

[Jagosaurus]

Hey man, I'm having the opposite problem... mine plays 2600 but not 7800 lol.

 

Topic: http://atariage.com/forums/topic/220365-7800-plays-2600-games-not-7800-games/page-2

 

Any input would be much appreciated.

 

Think any of these might help my situation?

 

 

1. re-flowed solder points for the color adjustment potentiometers
2. marked the original setting and twisted the color adjustment potentiometers to break up any corrosion.
3. adjusted the RF modulator pot
4. cleaned the cart slot pins and bent them out a hair for better contact