Symptom: Snagger releasing ball too early, or not lowering enough to grab ball.
Location: Lakewood, Colorado
The snagger mechanism on a Lost World pinball machine uses both optos and microswitches to determine the ends of travel. Or more accurately, the microswitches are wired in series with the motor to cut-off the power when at one end or the other. The game MPU has no knowledge that this has occurred. The MPU instead uses the optos to determine when it is at one end or the other. So the microswitches are acting as safety switches to stop the motor if the optos fail or are unplugged, etc. The game code also has a timer to flag an error and disable the snagger if it doesn’t reach one end or the other in the allotted time. When using the special test function in the Diag->Lost menu, the display will show the status of the optos, but relies on the switches to stop the motor at one end or the other. But during game play, the optos are used. So adjusting the switch levers had no effect.
Over time, the gears and belts develop mechanical play or slop. The original designer never accounted for this. The only adjustment is the center of travel, basically the flag that interrupt the optos. This can be loosened, rotated, and re-tightened on the motor shaft. One could also loosen one of the pulley screws and accomplish the same thing. But this only adjusts the center of travel. If I adjusted it so that the ball would release and fall into the Jeep properly, the snagger wouldn’t lower far enough at the other end to grab the ball. If I adjusted it to grab the ball properly, it wouldn’t raise far enough and the ball would release on the edge of the Jeep and just sit there.
The largest source of play is the cam on the left side of the last hinge of the snagger. As of this writing, Marco Specialties sells the shaft and the end housing of the snagger. I wasn’t able to remove the last pulley due to damage of the set screw, so replacing it wasn’t an option.
What is really needed is a way to move one of the optos so that the motor runs a little bit longer to account for the slack in the mechanics.
I removed one of the optos and with a very small Dremel bit, created slightly curved slots for the opto leads in the circuit board. This would allow for the opto to be adjusted.
Showing new position of opto before final adjustment in the machine.
Added wires to leads to allow for movement
After determining the ideal position for the opto and adjusting the center travel (as mentioned above), I put a little drop of hot-glue on the top side of the board at the end of the opto to hold it in place.
The snagger now works perfectly. Not the prettiest solution, but sometimes things need a slight design tweak. If there were more Lost World machines out there, I’d design an aftermarket board that would make this a lot easier.
