If you are having issues with the diverters on STTNG, I recommend reading through the writeup at Pinwiki found here. I especially recommend doing the modification to move the tieback wire and run it directly from the driver board to the auxiliary driver board.
As an update to the game that is discussed below, the problem with this game continued for years. The upper diverter would lock on, cook the coil, and blow the fuse. I had done everything in the Pinwiki article to no avail. The game would work for quite a while after repairs, but eventually it would lock on the diverter again. It seemed the game was possessed. It was finally determined that the issue was the ribbon cable that runs from the MPU board to the little auxiliary driver board. The game has been running trouble free for over a year after the ribbon cable issue was diagnosed. New ribbon cables can be ordered from Great Plains Electronics. Also realize that the problem can be the connectors on the MPU board and the auxiliary driver board. So keep this in mind while trying to diagnose and troubleshoot issues with the diverters on STTNG and other games that use an auxiliary driver board.
Below continues the original post regarding this issue:
I had the opportunity to work on a beautiful Williams Star Trek the Next Generation (STTNG). The game was not loading the under playfield balls correctly and was cycling the loading sequence.
Sorry for the lack of updates lately. It has been busy around here. This is a quick one, I’ve seen this quite a few times lately: flipper coils installed incorrectly.