If you truly wish to learn, young Luke, follow this lesson through to the end.
So an important part of LOGICAL troubleshooting is a principle called Paths of influence. I'll give you an example that might seem simplistic, but bear with me. Example, visualize a ladder diagram(schematic)like a pinball game has. One one side is a hot wire, and the opposite side a common, or ground. Lets say there are 3 circuits in our game, the first circuit has a wire from the ground line to a normally closed light switch, a wire from the other side of the switch to a 2nd N/C switch, then a wire from the other side of the switch to a 3rd N/C switch, and then a wire to a light bulb, and a final wire from the bulb to the hot line. Since all 3 switches are closed, as soon as power is applied the light will turn on. This circuit is labelled #1. There are 2 more identical circuits labelled #2, and #3. So when we apply power to our circuit and it's working correctly, all 3 bulbs will turn on. Now one day when we turn on the power, #2 lamp (the center circuit) does not light, but #1 and #3 bulbs are on.
SO the paths of influence principle says to first identify everything in the path of the failing #2 circuit . In this case the path of influence would include the wire connection at the hot line, the wire from there to the #1 switch, the switch itself, the wire to #2 switch, the #2 switch, the wire to #3 switch,the #3 switch, the wire from #3 switch to the bulb socket, the bulb socket, the bulb, the wire from the bulb socket to the common wire, and the connection of that wire to the common. The path of influence would NOT INCLUDE, any wiring, switches, bulbs, or sockets in the #1 or #3 circuits, because only the #2 bulb is not lit. These circuits have NOTHING to do with the #2 circuit, so should not even be considered. It would ALSO NOT include needing to check that power or common is present, since #1 and #3 circuits work, proving that power and common are there. You need to laser focus on the failing path/part and not be distracted by other (non influencing)parts of the circuit or weird symptoms. If you have a non energizing relay, or bulb in this case, that you KNOW should be working, STAY ON YOUR PATH AND FIND WHY IT'S NOT WORKING!
Now that we've determined everything in our path of influence in the #2 circuit, we can begin testing. The most efficient method is to split a circuit in half and begin checking for power in the approximate middle. This will quickly define for you which direction you need to move the testing in order to find the fault.
Actually as test equipment you can use jumpers, or a voltmeter, but actually the best testing device is a circuit tester. You can build this by taking a rubber covered alligator clip, solder an insulated wire on it about 6 ft long. Attach the other end of the wire to one connection of a bulb socket. Get a voltmeter type test probe(plastic shaft with the metal point on the end) and somehow attach the bulb socket to the non testing end of the plastic shaft/handle and insulate well. On the other connection of the bulb socket, add an insulated wire and run the other end of that wire through the plastic handle to solder it to the metal point (testing end) of the test probe. IN the bulb socket put in a bulb that closely matches the bulb of the circuit you are testing, and you now have the perfect test device for testing game circuits. At Pinball Expo, I once watched the great Gottlieb pinball designer, Wayne Neyens hook one of these test probes in a broken mid 70's Gottlieb pin that had the owners scratching their heads, and solved the problem in less than 30 seconds.
If you can truly take this method of troubleshooting to heart, and do not deviate, there is no such thing as trial and error, just trial and solution!
SO in your circuit, you actually did make some progress toward path of influence and logical (split the circuit in half) troubleshooting, but then you started deviating. What is our failure? The Rear Roll Over relay is not firing. But is that actually the problem? SHould it actually be firing when one of the rollover switches are closed? The only way to determine that is to measure and be sure we have a complete circuit to power the relay. If we do not have a complete path, and everything appears correct, then possibly you are not actually troubleshooting a problem.
In this particular case, we can fairly easily verify whether this relay should actually be operating now or not. How do we verify? For a relay (or light bulb) to fire we need a hot wire at one end, a common at the other, and a complete circuit in the middle. I'm going to assume in this case that you have the game powered up and coined with the game reset and operating. Since I don't know which color wire is hot and common(doesn't really matter for example) I'll just assume Yellow is common and Black and Gray are hot. In this case you've already smartly tested that the coil is good by jumping the black(hot) to the non yellow side of the coil. That proves out that yellow is actively common, black is actively hot, and the coil is good and the wire from the coil to the Yellow is good. You have NOT YET PROVEN that the coil SHOULD be operating though. Since the GREY WIRE carries the hot to this coil(AND NOT THE BLACK), you need to verify that in fact the grey wire is also HOT RIGHT NOW. If it is not HOT, this could either be a problem OR this circuit is not supposed to be operating right now. If the grey wire IS HOT(use voltmeter from grey to yellow to test), then we know that we have an active circuit, and can continue troubleshooting. IF the grey wire is NOT hot, you are not looking on the correct path of influence and should go elsewhere. I will assume the grey wire is currently hot and continue as if this is the correct path. Since this is a circuit with very few things in line, you already have logically gone to the middle of the circuit in your troubleshooting. So with grey wire hot, the only other items in our path of influence are the relay coil connection point of the R-Y wire, the wire itself, its connection at the first RO switch, the wires connecting the switches together, any individual switch, the connection of the wire where it leaves the switches going to the grey line, that wire, its connection to the grey line, and possibly any jones plugs that may be in that path.
One error was made in following the path was made by you when you jumpered from the game over relay(grey) contact to the R-Y wire. That relay has nothing to do with this circuit other than the fact that it has a grey wire going to it. THAT IS NOT THE SAME GREY WIRE GOING TO ONE SIDE OF THE RO SWITCHES. So the correct testing must stay in our path. That jumper should have been applied from the point on the RO switches where the grey wire is attached over to the other side of the switches where the R-Y wire is attached. If the relay does fire at this point, then we have isolated the problem to the bank of switches or the interconnecting wires. If it does not fire, and we've tested the main grey wire is hot, we have still NOT tested that the grey wire is hot all the way to where it connects to the bank of switches, and have not tested the R-Y wire continuity from the switch bank back to the coil. Somewhere in the correct path of influence lies the answer, my friend. Learn these lessons well, and someday you will be an EM Jedi. Best of luck!
Bel Air, MD
