I think you will find a reset relay in the cabinet at right side of motor board. Also a game over and tilt relay. A coin relay circuit ,I think I will never understand. There may be a 'hold' relay that stays pulled in during play. I'm not an expert and usually figuring many a thing out as I go. Gottlieb's legacy holders have made it impossible to share manuals and schematics(See: Greedy Pricks)So I can't look at any diagrams. It sounds a bit obvious but did you test all fuses for continuity and voltage drop across the energized fuses? I think I saw some fuses underside the playfield. Check the game over light bulb. That circuit should send power to game over lamp when the game is "relaxed" between plays. The game over relay initiates the reset sequence when credit button is pressed. I believe it sends power to reset relay.The machine will then continue to reset untill things like score reels at zero positions, reset bank completed, ball counter at start position, score motor at home position...ball in shooter lane?....
PS>>>The ball counter has to be at game over position{#'6'} to initiate the game over state.
PPS>>> Here's where schematics get confusing...AH, even more confusing?...A pinball schematic shows the state of things with the game powered on, reset completed AND in the ready to play ball #1 condition. This means normally open / closed contacts are shown at their game started position. The game over light is a good example of this. It will be drawn as normally open contacts(N.O.) because that circuit is off during game play. That set of contacts is held open by an energized relay coil on game over relay. When the last ball drains the game over relay de-energizes and that N.O. contact closes, sending power to the game over light. That is just how they(and you know who they are?) do things...C_S