Hello Everyone, This will be a bit longer opening post but I want to give you all the information and history I can so you can help me solve this problem. I have a Bally Star Trek that was given to me by my Aunt and Uncle who have had it the past 21 years. I grew up playing this machine and it has always had one fatal flaw: The top saucer.
Here is the symptom: The top saucer will periodically not kick the ball out. It will not trigger during the solenoid test fire sequence at the beginning of the game or in the test mode. Then periodically it comes back. It has done this for the past 15 years at least. The same goes for the Knocker. Then one day, suddenly they will all work.
Typically we just played around it and you just "got lucky" when the game worked but now that I know a bit more about pinball electronics I want to fix it. Here is what I have done to attempt to troubleshoot so far:
1.) New MPU Board (the last one had battery damage) - Thought maybe the MPU wasn't sending the signal (not the case)
2.) New coil under the saucer- Thought that the coil was bad and not energizing correctly
3.) Checked the pins on my solenoid driver board to make sure they weren't "cold" and needed re-soldered
-After step 2 I got lucky and put about 150 games on the machine without incident. A few weeks ago my game suddenly blew the f4 fuse. I posted on the forum here and someone directed me to put a new bridge rectifier in and that seems to have solved my problems for now but I can't help but wonder if the two are related as I still don't know what caused the original F4 Fuse blow. So onto my new theory about what is going on:
I think that I need to rebuild the connectors on my transformer board and maybe my J2 and J5 on my solenoid driver board. I think that power is not being transferred to those solenoids but- then again- I am new to this and don't have great diagnostic skills yet. What do you guys think? I've attached some photos of my board pins and schematics to help jumpstart the conversation.