STTNG — Trough, Gun Mech & Opto Board Repair

The Machine

This Williams STTNG (1993) came in needing attention on all the classic STTNG things; trough optos, the left gun mech, the main opto board, and a poor prior LED swap all needed addressing. STTNG is probably the hardest WPC game to maintain is which is unfortunate, as the game is really fun to play (when it’s working well).

Trough Opto Repair

Trough opto failures are extremely common on WPC widebody machines. Over time the opto board connector solder joints crack and fail, or the opto pairs themselves just die and stop reliably detecting balls. All trough opto connectors were reflowed, which resolved most of the issues — but one opto pair was still reading marginal after the reflow and had to be replaced outright. It’s still worthwhile to repair these boards as a set of new widebody trough boards are still $100 for some reason.

Note the missing switch 2 down in the 6th column, for ball 5 in the trough. This was causing issues and ending balls early after multiball or after final frontier when the guns are empty. Also the hackjob someone did reusing some old .100 molex connectors to replace the old IDC ones, that was not me!

Left Gun Mech

The left cannon was occasionally failing to fire. STTNG’s twin gun mechs are one of the signature features of the game, but are also one of the most failure prone parts of the game. The culprit was a bad gun harness — very common for the wiring for the coil to intermittently break and cause loss of solenoid voltage at the coil. The harness was repaired by someone else prior to me already, bypassing the harness with one wire and another for the opto was recrimped.

Opto Board Repair

The main opto board had sustained significant corrosion damage from a failed capacitor, extremely common on all WPC opto boards. The leaking cap had damaged components and traces surrounding it. The board was repaired with a new capacitor and the affected traces and components were addressed.

LED Swap Cleanup

A previous owner had done an LED swap using poor quality LEDs throughout the game. The backbox LEDs were starting to crack, presumably from UV or heat damage. When trying to remove them, they all broke apart! All of the backbox LEDs were replaced with Comet 2SMD frosted and should last the rest of the game’s life.

Result

With the trough detecting balls reliably, both cannons firing correctly, the opto board repaired, and the lighting sorted, STTNG was finally playing as it should. This is one of the most complex and beloved widebody WPC machines ever made — well worth keeping in proper working order.