By Russ Jensen

In the first article in this series on pingame troubleshooting we discussed the 'simple electric circuit' and the organization of a pinball schematic diagram. We shall next discuss the basic electrical components which make up most electromechanical games.


The earliest electrically operated pingames used dry cell' batteries to operate their simple mechanisms such as electric'kickers' and 'guns.' The normal operating voltage for these games was usually 4V2 to 6 volts D.C. (direct current). The circuits in these games were very simple, consisting only of ball actuated switches and solenoid coils making troubleshooting quite simple. The next step in pinball power evolution was to replace these batteries with a 'power pack' which could transform the 110 volt A.C. (alternating current) 'house current' into a D.C. voltage equivalent to the batteries. These 'power packs' consisted of a transformer, to reduce the voltage, and a rectifier which changed the alternating current (A.C.) to direct current (D.C.). The output of this device was connected to the pingame's simple circuits in place of the batteries which had to be replaced frequently.

Electric pingames became increasingly more complex in the mid 1930's. Lights were added and the games contained more and more solenoids to provide action and later to operate score registering devices. The many coin payout pingames utilized motor operated payout devices which also required electric current. For this reason batteries and' power packs' soon gave way to multiple winding transformers. Games for the most part utilized AC. operated components, a practice which continued (on electromechanical games) until the mid 1970's when D.C. began to be used again to power some action components such as 'pop bumpers.' One exception to this was Genco which utilized A.C. for lamps and D.C. (using a rectifier mounted on the transformer) to operate solenoids and relays on 12 to 15 volts D.C. (NOTE: Some, (mostly payout), pingames in the mid thirties utilized 'power packs' putting out from 12 to 24 volts D.C. to operate the entire game including motor, relays, solenoids, and lights. Some of these games used higher voltage lamps (such as 18 volt) but many used 6 volt lamps and 'dropping resistors' to lower the voltage.)

The transformer, common to most games from the mid thirties until the 'solid state era', usually consisted of three 'windings'; a 'primary" and two (or sometimes more) 'secondaries'. The primary was supplied power from 110 volt A.C. power (house current). The primary produced a magnetic field in the transformer's iron 'core,' which in turn causes currents to flow in the secondaries, which were wound to produce lower voltages than that applied to the primary. One secondary produced the voltage for all the lights in the game (almost always 6 volts) while the other one produced a higher voltage (usually either 25, 30 or 50 volts) to operate all coils and most motors. The voltage produced by each secondary winding was almost always indicated next to the symbol for that winding on the schematic. Bally (and Williams, until the early 1960s) were about the only companies to use 50 volts for coils. Most of the others (except for Genco's D.C. power) used 25 or 30 volts. Most 1-ball 'horse race games' and 'bingos' however, usually used a third secondary on their transformers which provided 18 volts used to power some lamps and coils from the same power source where doing so greatly simplified the circuitry. A word of WA R N I N G! These types of games contain both 6 and 18 volt lamps, interchanging of which will result in either lamp burnouts or dimly glowing lamps.

As was mentioned last month in the discussion of schematics,the outputs of the transformer's secondaries 'feed' the 'power lines' to the other game components. One side of the secondary suppling the coil voltage feeds the 'coil common' line in the game which is connected directly,or occasionally indirectly (through a switch contact) to every coil in the game.

The other side of this coil voltage secondary is connected to the 'return line' to which is connected one side of the switch circuits controlling each coil. Actually this 'return line' consists of two sections, one of which is connected at all times when the game is 'on' and the other section which supplies power to certain coils only when the game is being played (i.e. not at 'game over" or 'tilted'). Contacts on the 'game over" relay (if there is one) and/or the 'tilt' relay(or some type of lock hold or anti cheat relay) are used to break the connection to this section of the 'return line' at the proper time. It should be noted that malfunctions in these contacts are a major cause of a game not working as will be discussed in a subsequent article.

Similar connections are made to the tranformer's other secondary (which supplies low voltage to light the lamps throughout the game) which feeds a 'lamp common' and a lamp return line. In some older games the two 'return' lines (coil and lamp) were connected together at the transformer thus creating one 'return' line common to both coil and lamp circuits. In these games a malfunction could occur which could result in burn out of a large number of the lamps in the game. When the game was tilted (or at 'game over' in some machines) two relay switch contacts would open the power circuits; one in the common 'return' line and the other in the 'lamp common' line. If due to contact wear or misadjustment, only the switch in the 'return' line opened (the one in the 'lamp common' line remaining closed) circuit paths would be created allowing a high voltage to be applied across some lamps, if the game were being played, causing these lamps to burn out. For this reason adjustment of all contacts which open transformer circuits to common power lines should be checked carefully.

The 'common' and 'return' lines are wired to many components in the machine. This is accomplished by wiring to a solder terminal of a component and then connecting another wire to the same terminal to go to the next component, etc. If any of these 'double connections' are ever broken (one wire disconnected) the power to one (or in most cases many) other components will be lost resulting in major malfunctions of the game. This situation frequently occurs when someone has removed a component which for some reason they donít want to operate and did not reconnect the 'double circuit' which fed power to it. For this reason when such major malfunctions occur (i.e. several of the game's components not working at all) this power wiring should be checked carefully.

It should also be pointed out that each power circuit (coil power, lamp power and 110 volt power) will be separately protected by fuses placed in the circuit close to the transformer windings. These fuses are usually mounted on a fuse block' inside the front of the machine. The 110 volt line fuse is sometimes mounted separately near the transformer itself inside the game. On many later model machines, large current coils (such as relay bank reset coils) will be separately fused, the fuse mounted near the component it protects, The fuse sockets are usually labeled as to the size of the fuse (in amps) and the circuit it protects (6 volt, coil power, 110 volt line, etc). If one of these types of circuit is completely inoperative (i.e. no lamps light, no coils operate, or the game is completely 'dead) the fuses should be checked first. A burned out fuse can usually be spotted by eye looking to see if the small piece of' wire inside is broken. In some cases however a fuse may look O.K. but still be burned out. These fuses must be checked using an ohmeter or by trial replacement with a new fuse. When replacing or checking fuses, two cautions are strongly advised: 1) unplug the game when working near the 110 volt line fuse, and 2) always replace a fuse with the exact value indicated.

In addition to the components which operate from power supplied by the transformers' secondaries, a few components in many games operate directly from the 110 volt house current. These include some relays (generally in the game's 'start up' circuits), large solenoids, such as relay bank reset coils (more about those next month), and some motors (especially in 'bingos' and 'one-balls'). These circuits are usually shown on the schematic adjacent to the transformer primary winding. The wiring for these circuits in the machine can usually be spotted because a different type or size of wire is normally used than is used for the lower voltage circuits. Sometimes rubber or plastic insulated wire is used as opposed to cloth insulation used for the other wiring. In other games a much heavier cloth insulated wire is employed. In many cases the solder terminals where these 110 volt wires are connected to other components are covered by short 'slip-on' insulating sleeves to protect mechanics from inadvertently touching the wiring and getting an electric shock. These insulating sleeves are not always an indication of 110 volt circuits as some manufacturers occasionally use these on lower voltage circuits as well. In this respect a couple of words of warning are in order. These 110 volt circuits are generally the only ones in a game of which one should beware of touching, although 50 volt circuits can sometimes provide an annoying shock When working on these circuits, the machine should either be unplugged or extreme caution should be taken not to touch uninsulated connections. Most people do not realize that even if a game's 'on-off switch (if it has one) is off a shock is possible if 110 volt circuits are touched. So be careful!

This concludes the discussion of 'pinball power.' Next time we will start to discuss the other electrical components which make up an electromechanical game, such as relays, stepping switches, solenoids, and the like.

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