Centipede Upright Player 2 Trackball Issue - Repaired
Had a strange issue with an upright (not a cocktail) Centipede when it was player 2 turn. The archer would go all the way up on its own at the start of the turn, could not be moved down but would go left and right. Player's 1 trackball control was normal.
Looking at the schematics, there are provisions for joystick inputs for P1 & P2 as well as the normal trackball inputs. Using a Fluke and 6502 pod, I read memory location 0C03 (memory location for P1 & P2 joystick inputs) and sure enough it came back with FE (instead of FF) showing that P2 Up bit was active (with no controls attached).
Found C49 was almost a dead short which caused the game to think a P2 joystick was being held constantly in the up direction. Replaced C49 and now player 2's trackball controls are working as they should.
Just wanted to document and share...
Had a strange issue with an upright (not a cocktail) Centipede when it was player 2 turn. The archer would go all the way up on its own at the start of the turn, could not be moved down but would go left and right. Player's 1 trackball control was normal.
Looking at the schematics, there are provisions for joystick inputs for P1 & P2 as well as the normal trackball inputs. Using a Fluke and 6502 pod, I read memory location 0C03 (memory location for P1 & P2 joystick inputs) and sure enough it came back with FE (instead of FF) showing that P2 Up bit was active (with no controls attached).
Found C49 was almost a dead short which caused the game to think a P2 joystick was being held constantly in the up direction. Replaced C49 and now player 2's trackball controls are working as they should.
Just wanted to document and share...

