Repair 1 - Star trek STTNG left popper dead coil
So this is a quick one. Williams star trek game. Left popper coil dead. I hit the mode start, ball roles down in the subway and never comes out. I can hear the eject sound in the game ROM and the flasher triggers several times.
Since the flasher triggers a few times, I know this is not a switch problem. So I wonder if there are any blown fuses. Before testing those, I enter the solenoid test in the diagnostics menu. I test each coil. They all fire except the left popper. Since no fuse protects just this one coil alone, I know it's not a fuse.
Next, I want to check the coil to see if a wire popped off. I lift the playfield and examine the coil. The coil is fine. All wires are intact. I measure resistance across the lugs of the coil. (Coil has no diode). They read 4.3 ohms, which seems about right for a 23-800 coil, and this matches the readings from the other 23-800 popper coils in the game.
Next, I close the coindoor and set my meter to DC voltage. I measure power at the coil by putting the red meter probe on a coil lug and the other on the system ground strap. I read 72volts. So the coil has power.
Coils are triggered by having power, and the system grounds the coil when it should fire. So next is to test grounding the coil lug to see if it fires. I touch a wire to one lug and quickly touch the other end to the ground strap. System fuse blows. Oops, I must have touched the wrong lug and directly grounded power to ground. Replace the f105 fuse and try again. This time testing the other lug. The coil fires. This tells me the coil is good.
Next to check wiring. Looking at the coil chart in the system backbox, it says j107 pin 3 controls power and J130 pin 6 controls the transistor (ground). I get my meter out and probe pin 6 on J130 and connect the other end to my coil lug that didn't blow the fuse when I touched it to ground earlier. I get no continuity. Wire must be severed.
I trace the wire harness from the coil working my way to the back box and see the wire is actually broken. The wires in the game are sloppy and hanging pretty loose. I reconnect the wire to the other end using some heat shrink tubing, and tidy up the wires with wires straps. Test continuity at the board, and continuity is now there.
Fire up the game, and test, coil is fixed!