Got a call from a guy with a Metallica LE that was spitting two balls out into the shooter lane.
Most of the time when a machine spits two balls out, there is something wrong with the trough switches. If one switch isn’t registering properly, the game will be confused on how many balls are present and this symptom can appear as a result.
Every pinball machine has trough switches. Depending on the age, they may be a leaf switch, a series of leaf switches, rollovers or opto-based. This machine used an opto for the upkicker into the shooter lane and three rollover switches behind that.
I tested the opto with my trusty chopstick (these things are perfect for testing switches in precarious areas where you don’t want to be sticking something metal when the game is on!). The opto was fine, and actually so were the three rollovers; however, sometimes the rollovers can be maladjusted where they work from a functional standpoint, but aren’t engaged properly when the ball is on them.
So, I removed the trough and made some adjustments to the rollover switches and rolled a ball slowly over each one ensuring I heard the proper “click”. I put the trough back in the game, loaded back in all 4 balls and then play tested 3-4 full games. Everything functioned as it should and MET LE is back to putting one ball out at a time.