Theatre of magic

The main reason for this game to be here is a problem with the trap door. It’s lifted but then falls back again before the ball is ejected. The trap door is controlled by a flipper coil with a high power winding to lift it and a low power winding to keep it open. Since it is a flipper coil I first suspected it was driven by the fliptronic board and the problem should be found by the hold transistor, but that was way wrong. It is instead controlled by two transistors at the power driver board. I checked the voltage at the collector at the holding transistor and it was nothing at all there. I should have been able to measure +70v at the collector as long as the coil isn’t energized. Since there was no voltage at all at the transistor I went down under the playfield and measured at the coil and there was no voltage at the hold winding tab either. The cause turned out to be a bad soldering where the coil wire is connected to the soldering tab. I removed the whole trap door unit from the playfield to make a proper repair at the work bench. And since I had it out of the playfield I took it apart to clean the parts.

 

 

While working with it I found a couple of other problems. Two screws were missing at the micro switches where the balls line up, a wire was almost loose at the VUK micro switch and somebody had been oiling one of the plungers. Never oil anything in a pinball unless the manual clearly state that it should be oiled. When the oil is fresh it might look like it did the trick, but it will soon gum up and cause a lot of problems.

 

  

The trap door unit is now refurbished and ready to go back in to the playfield. But it will have to wait, there is a lot of other bits and pieces at the playfield I have to go through first.