This is the EM Journeys Pinball Podcast. Hello and welcome back to the EM Pinball Journeys Podcast. I'm David Morgan, and I'm glad you're joining me for another episode. This is the third episode in the beginner series designed for those who are new to EM pinball or pinball in general. Today we're going deeper into EM pinball terminology, exploring the inner workings and anatomy of these amazing machines. In the last episode, we focused on the player facing elements like the playfield, cabinet and back box. This time we'll venture beneath the playfield and behind the back glass to uncover what makes an EM tick. Even if you're just a casual player with no intention of owning or repairing a machine, I think you'll still find today's episode fascinating. Let's get started. When I looked inside an EM for the first time, I was surprised at how many wires and mechanisms it takes to make a pinball machine operate. The EM pinball machines of the 1970s are much more complex than the earlier machines in the 1930s and 1940s. Innovation and competition drove the designers and manufacturers to continually create more features to attract more nickels, dimes, and quarters. First up, the transformer. Inside the cabinet, you'll find the transformer, which is the center of the electrical system. The transformer is a metal-cased component that steps down the voltage coming in from the power cord, known as the line cord. In other words, the transformer lowers the amount of electricity to provide the appropriate voltage needed in the different circuits throughout the machine. Components that move in a pinball machine need more power than, say, the lights. Because of that, the lights are on a separate circuit. I'm looking at a Gottlieb pinball machine from 1973 and coming from the transformer, there's a 6 volt circuit to the lights and a 25 volt circuit to everything else basically. This is a lot less power than the 120 volts coming in from the power cord. I'd like to add here that safety is very important. It is strongly recommended to work on a pinball machine with the power off and unplugged. Even when the machine is off and plugged in, there is still a dangerous amount of electricity going into the machine. The wires that come out of the transformer are connected to fuse blocks. The fuse blocks protect circuits from an unsafe amount of electrical current. Each fuse block is connected to two or more wires and holds a fuse. The fuses found in EM pinball machines are small cylindrical components that resemble a glass or ceramic tube. Fuses have metal caps at both ends which are used to connect the fuse into its holder, the fuse block. If there is an overload or short circuit, the fuse inside the fuse block will blow which breaks the circuit. The idea is to prevent damage to the wiring and components. Fuses are typically transparent and fuses made of glass allow you to see the filament inside which is designed to melt and break if the current exceeds the limit for that fuse. In an EM, a fuse might be as small as a quarter amp or as high as 15 amps. I'll cover fuses in more detail in the future, but they should never be replaced with a higher amperage. Otherwise, there is a risk of overheating and fire, as well as potential damage to components. In EMs, fuse blocks are typically located inside the cabinet. Typically, many of them are together near the coin door. Often, they are also in separate locations, such as underneath the playfield. I mentioned the on-off switch in the last episode. The on-off switch is typically on a circuit wired between the transformer and a fuse block that connects to the power cord. EMs have no integrated circuits and relays control the functions of the machines You can think of the relays as the hardwired programming and with the help of the score motor, relays make decisions, so to speak, as they activate and deactivate things throughout the game. There are a lot of electromagnets inside an EM. Each relay has a coil of wire that, when electricity flows through, it magnetically pulls an armature, which is a metal plate connected to a plastic tray with slits holding switches with contacts. As the armature is pulled in, the bottom blade from one of each set of switches moves and changes the state of the switch. A switch is typically two blades, and sometimes more than two blades, of metal connected to wires that are used to temporarily complete a circuit. There are tiny round contacts on each switch blade and when the contacts on the switch touch, an electrical connection is made, and current flows through the switch and its connected wires. Closer to where the wires connect to the switch is an insulator that helps keep the blades separated so that only the contacts touch together. This type of switch is used in various parts of every pinball machine and is commonly called a leaf switch. Some switches are normally open, and when the state of the switch moves to closed, a circuit is completed or is considered closed. The contacts on the two switch blades were pulled together. Other switches are normally closed, and when the relay pulls the armature in, the switch blades and the contacts separate, and that circuit is now open, and there is no connection. For example, if you hit a target, a light might come on, or a light might come off. The switch on the target sends a signal to the relay that either turns on the light by closing a switch or turns off a light by opening a switch. There is a third type of switch. So far I talked about a normally open and a normally closed switch, which typically have two metal blades. The third type is called a make-break switch, or sometimes called a break-make switch. This switch is typically three blades, and when the switch state changes, the middle blade with contacts on both sides is moved back and forth. At rest, a make-break switch has two of the three blades making contact. When the switch changes state, the middle blade moves away from the blade it was just touching and toward the opposite third blade, and then the contacts are touching only on the middle blade and the opposite third blade. If you hold up your middle three fingers and move only your middle finger between the other two, that will give you a sense of how a make-break switch moves. Switch blades sometimes need to be adjusted with a switch adjuster tool that helps bend the blades without damaging them. Setting the proper amount of space between switches is called gapping. If the contacts are too far apart, they may not make a proper connection, and if they are too close, the gap may cause an unintended short circuit. Relays can have as few as one switch, or they may have many switches and control several operations simultaneously. A grouping of switches that are stacked on top of each other are called a switch stack. Depending on the function, a relay may be activated only briefly or it may hold on for a long period of time. When the electricity is cut, the armature is no longer being pulled in toward the coil, and a spring assists in returning the armature and the switches back to their deactivated state. Another type of relay is called an interlock relay. An interlock relay has two coils that activate a set of switches back and forth. This is used when switches are used in one state or another for a longer period of time. When one of the coils is activated, we also say when one coil fires, the armature is moved to the corresponding position. The coils only need to have enough electricity to move the switches back and forth so the state of the switches can be maintained without electricity until a change is needed again Some Pimdall machines have a bank of relays that can be reset together This is called a trip relay bank Trip relays are typically a few relays up to a dozen that are together A trip relay changes the state of switches with an armature by the trip coil being activated. Each relay has its own trip coil. The trip relay can hold the state of the switches without power until reset. There's typically a reset coil that resets the relay bank to its preset state. The reset coil is typically a solenoid coil. A solenoid coil is larger than a relay coil, but also is a coil of wires. A solenoid coil is hollow in the center so that a metal plunger pulls into the hollow part when the coil is activated. A solenoid coil is used in many parts of a pinball machine. Almost everywhere there is movement within a device, a solenoid coil or two are involved. In the above example, when the plunger pulls into the trip bank solenoid, the relays are all reset together. The most commonly used solenoid is in the flippers. Each flipper is activated by pressing a button, and underneath the playfield the corresponding solenoid fires, pulling the metal plunger into the coil, which is linked to a mechanism that lifts the flipper in the upward position. Pop bumpers, slingshots, and kickers all use solenoids.