Have a Stern Grand Prix that i stripped down and repaired, and it went OK for a bit, then started getting stuck in the outer racetrack (ie: would never enter the playfield).
Now its constantly doing it. Launch the ball, and it just keeps going around the outer racetrack. I am thinking there needs to be certain conditions met for it to open the right diverter to allow the ball to enter the playfield, adn wonder if its something to do with timing of optos OR if there is a switch issue.
What i have done:
* Tested many many times the track test - all optos work 100% of the time, and i've watched the ball go around and around for minutes in the test with no optos missing (3 lower and 2 upper sets of optos)
* Tested the launch switch - works 100% of the time
What i find strange, is that if i start a game, and the ball keeps lapping around, and manually place it on the playfield, some of the coils do not fire (slings). Flippers and pop bumpers work fine. Its not until i hit the car mech, that the other coils start working.....
Another potential clue, is that the machine does come up with a tech error to check sw 39 which is car mech down. Now i have checked and double checked this switch, and it works 100% in the switch test (using the mech, not my finger), as well as 100% of the time in the car mech specific test - yet the machine keeps saying to check it in the tech alerts section of the menu - anyone have any idea at all why this would occur?
I even tried disabling the track, yet not sure how this is meant to work, as it still wouldn't enter the main playfield
I notice in the Grand Prix specific adjustments, there are to menus for 'Track Adjust' but the manual says "For factory service use only" so no idea if this can change the timing of anything to get the game to correct itself?