Replacing the Drop Target Assembly on Star Trek: The Next Generation. Not.
This serves as cautionary tale rather than a project description. The project will come later. But I felt compelled to post this as a reminder to others--and me--to always look for simple fixes FIRST.
About five months after adding TNG to my collection, I was messing around under the playfield trying to figure out an intermittent glitch (a fairly unimportant but annoying one). I was unsuccessful. But, in the process, I somehow caused a game-crippling problem.
The guts of TNG are complicated, with a "subway" system that redirects balls to various locations pretty much every time one drops under the playfield. There are two diverters that steer the balls to the correct locations. Suddenly, these had stopped working, as had the single drop target under the Borg ship that automatically raises and lowers to control whether the ball feeds to the bumpers or into the subway.
Tracing the connections (with the help of some online guides), I saw that one wire runs to all three of these coils--the drop target coil and the two diverter coils. The solenoid test confirmed that all three had stopped working.
Because the drop target was the first coil in the circuit, I concluded that it needed to be replaced. It had a problem with the automatic raising and lowering thing from the time I got the game, so I assumed--a bad word, I know--that it had finally died altogether.
I ordered a new assembly from Pinball Life and set aside a Saturday to replace it. As i was preparing to disconnect all the wires and remove the existing assembly, I noticed that there's a diode that bridges two of the contacts on the drop target switch. There isn't one on the new assembly. So, I went back to the Internet to see what that was all about.
When I did, I came across a page where another owner had described my exact issue, and explained that replacing a fuse (F103) fixed it. I had looked at the fuses, and I hadn't seen any issues. Now, I looked at F103 again and it STILL didn't look blown. But I had replacement fuses on hand and I figured, what the hell? It was worth a try.
I swapped in a new fuse, turned on the game and ran the solenoid test. It worked.
The moral of the story: always try ALL the small, easy stuff first. Even after 20 years of collecting games, I sometimes forget that.
I'll need to replace the drop target assembly eventually (to fix the raise/lower issue), but the game is operational again. And that project can wait for another day.