Just want to emphatically second what Talon2000 and others have said about crappy sockets. I have fixed a handful of boards where either the only issue or the main issue was crappy old sockets. In particular, these sockets:
This is on an Asteroids, but they can be found on many golden era Atari boards. I've also encountered them on Exidy games.
They're easy to recognize by the "horns" on the outside edges, They usually have a thin strip of white plastic on the bottom, though these don't for some reason. They're extremely unreliable and should almost always be replaced. They often crumble to pieces when you extract them.
I suspected the sockets on this board, so I went to pull the ROMs. The whole frame came up with it:
These come in 16-, 24-, and 40-pin varieties. Replace them all.
Some recent repairs:
- Centipede. Came up in game mode with all the mushrooms on the left edge of the screen. Watchdog in test mode. Replaced sockets @C2 (CPU), @C3 (POKEY), @F7, @H/J7, @D1, @E1, @F/H1, and @J1 (all ROMs). Issues gone.
- Battlezone. 3D drawing glitches after warm up, objects drawn all over / in the wrong places. Replaced sockets @D/E2, @F2, @H/J2, @K2, @B/C2, and @B1, @M1, @L1, @K1, @J1, @H1, @F1. Issues gone.
- Asteroids. Watchdog in game mode, intermittent watchdog in test mode, intermittently indicates RAM errors. Different RAM errors at different times. Replaced socket @N/P3. Issues gone.