I'm looking for assistance in repairing an Atari 400. It has an intermittent issue with graphics. Sometimes it starts up fine and everything looks normal. When this happens the graphics and colors are fine until the computer is powered off. Other times the colors are off on startup, for instance sometimes when playing Donkey Kong from a cartridge the graphics on the title screen are green. Other times it starts with a white background. The only way to resolve this is to power cycle.
Other times sprites are missing. For instance when playing Pac-Man from a cartridge Pac-Man and the ghosts are missing. You can still control the invisible Pac-Man by following the dots as they disappear. You will never die from hitting a ghost. Sometimes when playing Donkey Kong the Jumpman character is missing and just a solid vertical line runs down the screen at the position he should be in. Again only power cycling will resolve these issues.
Any ideas what can cause this? Could it be the ANTIC?
Any help would be appreciated.