Invisible sprites

[DenNorskeGutten]

I recently purchased an Atari 2600 on eBay. I already owned a number of games but had no working Atari. When the one from eBay came I got it all hooked up and for the most part it is working. Certain games, however, have serious problems. In Frogger, for instance, either the frog is invisible or the cars/logs on the same row as the frog are invisible. In Asteroids either the ship/bullets are invisible or the asteroids are invisible. I'm having similar problems with Space Invaders, Yars' Revenge, Missle Command, and Defender. Of the games I've tested, Pitfall, Bowling, Combat, Berzerk, Pac-Man, and Air-Sea Battle seem to work fine.

 

Is this invisible sprite problem an issue with the system or the cartridges? Is there any way I can fix it? I may be able to swap some parts with another broken Atari I own.

 

Some screenshots I took with my TV tuner card:

[Thomas Jentzsch]

The carts with problems you describe are using flicker to display more objects than usually possible (though Pac-Man should have problems too, how many ghosts do you see?).

 

It sounds like you 2600 or TV is only displaying every 2nd frame.

[DenNorskeGutten]

Thanks a lot! I think my TV tuner card uses frame skipping to cut down on the CPU usage. When I hooked it up to a normal TV set it worked fine. I was afraid I was going to have to send the Atari back.

[D.Yancey]

Thomas,

That was a very cool example of Troubleshooting!! I am impressed with that one.