Fixing ST:TNG

I mentioned in an earlier post that I was fixing two pinball machines: The Addams Family and Star Trek The Next Generation, as a part of a deal.
It's almost touching to see how naive I was, saying: "Next up is ST:TNG, which has some cannon problems, among other things."
AMONG OTHER THINGS, FOR SURE! ST:TNG is infamous for having a lot of problems, due to the complexity of the game under the hood. There's a lot of things that can go wrong, and a lot of it had done just that on this particular machine.

The seller said that there was some cannon problems. The flippers needed a rebuild. And sometimes during multiball, the game seemed to reset.
I started with the easiest part, rebuilding the flippers.

Next, I tested the switches. I found out that the left ramp entrance switch wasn't working, due to a broken lead. I didn't have any other color than black laying around, so that would have to do.

 

 

The owner wasn't happy with the speaker cover, so at some point he had purchased a better one, but he hadn't actually swapped them yet. Not a big job, but everything takes time. I should have taken a photo before the switch, but at least you can see that it looked OK after.

During solenoid testing, I found a couple of strange things. Switch number 40, top drop down, was not working, and also not drop up and some under playfield diverters. I found out that they were all connected to fuse F103. Additionally, another under playfield diverter wasn't functioning, and I found that the solder had come loose and the wire had fallen off that one.

Anyway.. What was going on with those other solenoids? It seems the previous owner had done a little trick. The game is supposed to have 6 balls installed, but now it only had 5. That actually functioned as a cheap workaround, because the game almost seemed to play correctly with the 5 balls installed. When I added one more, everything went wrong! The balls were shot out from the shooter lane, seemingly went around the game, under the playfield, went into the through and back out the shooter lane again. This was repeated over and over.

The purple-green wires had deliberately been disconnected from the drop down target solenoid, so I knew that this was something the previous owner wasn't able to fix.
The solenoid was non-working, so I replaced that and soldered the wires back into place. It seemed like the solenoid had killed its transistors on the 8 driver board when it died, so I had to replace those too.

 

 

I replaced fuse F103, and I thought the problem was fixed. And it really looked like it was, but whenever I started a new ball, there was a tick-tick-tick sound, almost like from a strobe light. And sometimes F103 blew again.

It took a long time to figure out what was wrong. The diverters also made sounds that fooled me into looking in the wrong places, but with the help of a friend I found out that the sound came from the drop down coil trying to rapidly pull the target down. It turned out that the switch which is supposed to sense that the target is down was dead, so the game kept trying to pull the target down again and again.
However, just replacing the switch didn't help. The old switch arm had seen better days, and it was difficult to bend it in such a way that the switch was activated just at the right moment. I replaced it with a new and straight arm, and it looked better. But it seemed quite hard to pull the target down. I replaced the spring that's pulling it down, but that only helped so much. The plastic piece didn't slide freely, it was actually slow, almost as if it needed some grease. I found out that the little spring that's supposed to push the plastic rod inwards and lock the target in the upright position, was just too strong! I cut about one and a half coil from it, and it worked perfectly!

The seller had told me that the game had some cannon problems, but I didn't realize what they were until quite late in the repair process. I guess I was just too focused on all the solenoid problems I struggled with. It turned out that the opto that senses the ball was dead on the left cannon. Once again, I found that a wire had lost continuity, so I just replaced it.

Still, sometimes when I played the game, the cannons wouldn't react when I pulled the trigger. After some testing in the switch menu, I found that the trigger switch was just adjusted wrongly, so that sometimes it wouldn't fire. It was just a matter of repositioning it slightly, and now the cannons always work.

I have now played some 30-40 games after the repairs, and I haven't experienced any problems. It's almost like I don't dare to write it.. I'm afraid I will jinx it!
The problems I mentioned may not seem like much, but believe me.. It took a lot of time to figure out everything that was wrong with the drop down target situation. I spent a lot longer fixing this machine than I had imagined beforehand, and I guess I have learned that I will be more careful before making such deals in the future.
At least I had the foresight to say that I would only fix the game functionally, and not polish or "shop" it in any way.

The owner is coming to pick the game up in a couple of days. Even though I have developed a love/hate relationship for the game (more on the hate side), I can appreciate that it's a fast and complex game with wonderful flow which plays great when everything is working correctly. However, I can't wait to get it out of here, so I can continue working on my game room.

If anyone ends up reading this because they are working on a Star Trek TNG pinball machine.. I feel your pain! :-)