I just had some BT’s BBQ for lunch and was getting ready for my long trip home to Bucks County PA after another great Pintastic weekend when I bumped into my buddy George. He wasn’t looking too happy. The playfield was up on his Oktoberfest (yes I know it isn’t in the picture) and he was trying to fix the knocker. It wasn’t working; he had a replacement add-on board and two knocker coils. The add-on board is located in the cabinet and drives some cabinet LED’s, the knocker and the shaker motor. He was having trouble getting the old board out due to plastic clips holding it in and I figured I’d help him out.
After swapping the add-on board the coil still wouldn’t fire. George also had a replacement pigtail that runs between the add-on board and the knocker and I swapped that next. While plugging it into the board I noticed one of the .156 pins pushed out of the connector housing. I pulled the pigtail back out and removed the pin. The crimp was defective, the pin was mangled during crimping and it really wouldn’t have made reliable contact so I cut both pins off and replaced them with .156 trifurcon pins.
Still not getting any activity from the knocker coil I decided to swap the first of two replacement coils in, nothing, tried the second one and still nothing. I figured I’d double check the fuse, it looked ok but when I measured it with my meter I found it was blown, swapped in a replacement and still nothing. So now I’m back to plugging in the original knocker coil, which I left screwed to the cabinet in case it wasn’t bad, it still wasn’t working.
At this point, I’ve tried two different add-on boards, two pigtails and three different knocker coils and still have no functioning knocker. So what’s left? I pulled the fuse again; it looks ok but to be sure, I checked it again with my meter, it’s blown. Now I know something is blowing the fuse so I measure each of the coils. Here’s the problem, one of them is shorted the bad one measures .3 ohms while the other two each measure 4.0 ohms. By the way, the bad one is one of the replacements.
Again, I replace the fuse and try using the knocker originally in the game. While connecting it one of the wires pulls out of the connector pin (on the knocker coil), leaving the pin in the connector body. I could have fixed it but I was out of pins since I didn’t have my full connector tray with me and I felt it would be better to send it back to American Pinball so they can see it for future troubleshooting purposes.
I should mention that most games have the wires soldered to tabs on the coils. American Pinball uses coils with .093, three-pin Molex connectors and the diode is crimped into the connector with the wire leads. This makes coil changes easier.
So this is it, I’m left with one possible coil and a partially repaired pigtail. I put the game into test and tried firing the coil. STILL NOTHING, until I wiggle the connector between the pigtail and the knocker and it works! Let it go and it stops working again. I pull the pigtail out and only had one shot to fix it. I only had one .093 female pin that happened to be lying in my tool tray. I remove one pin and it looks ok. I remove the other pin, it wasn’t crimped properly and not grabbing the wire. The crimp is defective and the pin won’t make reliable contact. I replace the pin; put it back into the game and now the knocker fires every time.
Now George is happy! His knocker works and all is well. I hate working on a problem and not having the time to complete the repair so I’m happy too.
After all of this I’ll stress that many problems are simply in connection points. If you are having trouble with your game and several parts swaps aren’t fixing it, it’s time to look closely at your connectors. This is one of the reasons that all header pins on older games’ boards need to be reheated and inspected for cold solder joints.