Asteroids interesting symptoms

Here's one I'm sharing just because of how interesting it is. I have an -02 version of Asteroids that plays just fine except:

1. Locks up (blank screen) when switching into test mode, but will pass self-test when powered up in test mode.
2. Same lockup when switching out of test mode, but will play fine when powered up normally.
3. Plays as many single player games as you like, but if you play two player, at the end of the games it never flips the screen back from player two to normal nor does it allow you to start another (single or two player) game (but goes into attract and looks fine with P1 and P2 flashing).

I'm planning on swapping the program ROMs and/or RAM, but if someone can think of a more clever culprit that would cause theses symptoms, then... well, they win respect and... appreciation. I've looked through the schematics and it's actually not too clear how the inverting circuit gets controlled by the program.

-Douglas

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Received on Sat Sep 8 20:07:57 2012