The majority of Williams coil part numbers indicate the construction method of the coil. The first letter or two indicates the type of sleeve, the position or length of the wire terminal lugs.

Example of a coil part number AE-23-800   In our example - 23=wire gauge; 800=number of turns of wire.

Coil Body and Stop Differences - Bally and Gottlieb use the same coil body. A typical Williams or Data East coil uses a 1/16 of an inch shorter coil body. As a general rule, Gottlieb and Bally used a 1 1/2 inch coil body (with a 1 5/8 inch long coil sleeve). Williams used 1 5/8 inch coil body (with a 1 3/4 inch coil sleeve). Replace a Gottlieb with a Bally manufactured substitution coil but only if a genuine Gottlieb coil is unavailable.
A thin round spring metal ring spacer was often used by Gottlieb and Chicago Coin games between the top coil bracket and the solenoid coil to keep the coil from moving when it is activated. These can often be found on Bally / Gottlieb pinball games to allow for a Williams coil substitution. This is not a legitimate use for this spacer ring, however it is commonly found on old EM and early solid state games for erroneous coil substitution reasons.

A Coil Stop is the metal bracket located usually at the bottom end of a coil (near the wire lugs or the coil's plastic base). It is used to hold the coil to its mounting bracket and to stop the solenoid plunger at the end of its travel.

Vast differences exist for coil stops between pinball manufacturers. These differences include stop bracket height, width and mounting hole spacing.
Coil stops can become magnetized by the coil's magnetic field or "mushroomed" from repeated solenoid plunger/core to coil stop impacts and are the second most likely cause of slow to operate or jammed solenoid plunger problems. The number one reason for slow to operate solenoid coil mechanisms is dirt or coil overheating resulting in a melted plastic coil sleeve
Normally solenoids are designed to operate without any lubrication. Application of any type of oil  is NOT recommended and can cause jamming or in some cases grease/plastic fires!
Flipper coil stops are very prone to magnetizing due to the strong magnetic strength of the flipper coil windings. A magnetized coil stop can cause a solenoid to be sluggish. The only sure way to solve a problem with magnetized or mushroomed coil stops is with replacement.

Bally/Williams pinball solenoid coils have places for three terminal lugs; left edge, middle, and right edge of the coil's plastic base. The positions are as viewed with the lug end of the coil facing you and the lugs on top of the plastic coil base.

The 'AL' and 'AR' coils are used when the lugs on an 'AE' coil would be in the way of a metal coil mounting bracket or any other close mechanical device.

AL has lugs on the left and middle. AE has lugs on left and right (both corners) AR has lugs on the right and middle of the coil base.
Part number suffix or Prefix (numbers or letters following a coil part number) - AE-23-800-04) and letter and number prefixes (SA3-23-850DC) indicate the following coil modifications - coil sleeve type used (metal or plastic sleeve and length), diode polarity, wire lug placement, length of the wire lug at the base of the coil or the length of the mounting insulator or coil base. The higher the American Wire Gauge number, the smaller the diameter of wire. A small diameter wire has more resistance then a large diameter one and will take fewer turns of wire for a given coil supply voltage.  This makes the coil cheaper to manufacture because wire is sold by the pound and not by the length of the spool of wire. This can also lead to a coil that is easy to burn because a small size wire will heat up faster then a large diameter wire.

The first digits in the coil part number (Ex. AE-23-550) indicate the American Wire Gauge (AWG).
The last set of part number digits (Ex. AE-23-550) indicate the number of turns of wire on the coil.

Our example solenoid coil (AE-23-550) would be a very strong coil. A typical use for a coil this strong would be in an outhole ball eject mechanism. An outhole ball eject device is only activated for a short period of time but must push a heavy game ball up a steep slope or lift it out of a hole to move the ball into the ball shooter lane.

Coil pull in strength:  The greater the number of turns of wire on a coil the weaker the solenoid coil. The fewer the number of wire turns the stronger the pull-in strength of the solenoid coil.
Raising the power supply voltage was used over the years to increase the strength of solenoid coils in arcade games. An increase in voltage allows a coil designer a wider range of coil strengths, an easier way to 'tune' the coil's strength to the pull in force required and increases the upper maximum strength level a coil. High coil supply voltages (greater then 24volts) tends to make a coil easier to over heat, increases the likelihood for the game's player to receive a shock and usually requires more turns of wire then a coil designed to work at a lower voltage.
The type of coil supply current can also effect the power of a solenoid coil. Direct Current (DC) offers approximately four times the strength of an Alternating Current (AC) coil with the same supply voltage.

Weaker coils (large number of turns of wire, Example a relay coil with 6000 turns of wire) can withstand longer activation times with overheating. Pinball solenoid coils are never activated for more then about a quarter to half of a second during normal game play (Electro-mechanical pinball coils are activated for a much longer time then on an electronic pinball game). If a relay or coin lockout coil is built with enough turns it can be activated indefinitely without overheating and eventual coil destruction.
Coils that may be activated for a long period of time (either by design or by a faulty/shorted playfield switch on an EM pinball) usually have at least 1300 or more turns of a large diameter wire. Score reel, chime, 'lock' relay and the 'hold' coil on most early two winding flipper coils are examples of a coil designed to be activated for a long time without overheating.

New Coil suppliers often offer "Hot" or "Extra Strong" solenoid coils as a way to "upgrade" a game for faster play or perhaps make a particularly hard to make skill shot on a steep ramp easier to obtain. These coils are modified regular stock coils with a few turns of wire removed from the coil (often resold at a premium price). These aftermarket coils usually don't last very long in a game and are not recommended. They can often break playfield or other hard to find game parts with their increased strength.  Non standard coils can over burden already stressed coil drive electronics shorting their life spans.
"High Tapping" a game with a normal line voltage is also not recommended as this can cause coils to overheat. Fixing or repairing the game's power supply is vastly superior to increasing the power supply voltage through "High Tapping" a game.  See our Tech Tips page for more info on high tapping the game's transformer. Flipper coils usually have two sets of part numbers (Ex. 21-550/26-1200, EOS flipper wiring) because they have two coil windings on the same solenoid coil body. The first set of part numbers (21-550 in example) indicate the strength of the flipper (pull in coil used to raise the flipper). The last set of numbers (26-1200) indicate the coil strength used to hold the flipper fully upright (solenoid core hold in coil). The number of wire turns on the second set of the flipper coil part number is always larger then the first number of wire turns because the coil does not need to be strong when holding the flipper upright does have to be able to be held in (coil activated) permanently without burning up the coil.

Flippers on modern pinball games (Dot Matrix Display pinball games) use only one coil winding. One winding flipper coils are supplied with two different voltages at different times in the operation of the flipper. (One winding flippers are sometimes referred to as "solid state" flippers even though they are still operated by a solenoid coil. They are driven by solid state electronics (driver transistor instead of directly from the flipper buttons). A higher voltage (usually 50 volts) is used to move the flipper and a lower voltage (usually 18 volts) is used on the same flipper coil winding to hold the flipper upright.
This new type of flipper coil doesn't have two sets of coil winding numbers in its part number. In fact, single winding flipper coils usually have only an arbitrary, non-specific part number on them (example; 090-5020-20). The part number doesn't indicate anything about how the coil was constructed or its pull in strength. One coil winding flipper coils can be identified by a flipper strength chart using the coil's wrapper color or by simply using the game's manual. However, Data East and some other pinball manufacturers liked to use a wrapper less coil with only a small part number sticker that usually burns up with the coil.

Coil Voltages - Early EM pinball and late model electronic games use a relatively high 50 volt solenoid coil voltage. This high drive voltage produced coils with very strong pull in strengths and a wider range of coil strength adjustment then the much lower voltage 28-39 volt solenoid coils. Caution: Anything over 48 volts is considered dangerous by an electrician. Wear rubber gloves If you are not comfortable when working with these higher voltages.
Higher coil voltage speeds up the game play and allows for mechanisms that have to physically lift a game ball and plunge it back onto the playfield. (such as a Vertical Up Kicker (V.U.K.)). The 50 volt source was abandoned during the "middle ages" of pinball (late 70's to 80's games) because of the shock potential of this high a voltage. Players could receive painful shocks if the game was not properly grounded either by the grounding lug on the power cord or by a missing ground wire on a metal game part.

If a coil needed more strength or a slightly faster plunger pull in speed, then the Alternating Current power supply was converted to Direct Current for only a few coils inside of the late model EM or early electronic pinball game.  This current type conversion (AC to DC, converted by bridge rectifier) was done mostly on Pop Bumpers and Sling Shot coils during the middle ages of pinball.
The higher 50 volt supply (DC current) was reintroduced in late model pinball games because game metal parts grounding methods slightly improved and the typical game player demanded higher game speeds. Stronger flippers were needed for the steeper sloped ramps and playfields of the modern pinball game. Also, greater playfield mechanism complexity began to be used on modern (Dot Matrix Display or DMD) pinball games requiring very strong solenoid coils.

Differences in Coil Driver Circuits - Old model Williams/Bally Electronic pinball games use bipolar driver transistors to supply Direct Current to an activated coil. Usually, but not always, transistors (tip120) are used to ground one side (wire lug) of a solenoid coil in an early solid state pinball game. The other coil wire lug is connected to the appropriate supply voltage for the coil to be activated. One transistor supplies the positive voltage and the other the ground to the activated coil.
In later model games, both sides (wire lugs) of a solenoid coil have a transistor connected to it. Both transistors have to be activated before the solenoid coil will activate. These types of circuits are commonly referred to as a solenoid coil matrix.
All DC (Direct Current) coils use a coil diode across their terminals to absorb the voltage spike caused when the coil is deactivated. Unless this diode is incorporated into the coil driver circuit board. Changing a coil with a - DC after the part number to an Alternating Current (AC) coil can be accomplished by removing the coil diode across the coil's wire lugs. A coil diode can also be added to an AC coil to make it compatible with direct current activated coils. The AC or DC coil's part number must match the required coil before a current type conversion can take place. Compare the wire size and the number of turns on the replacement coil with the original coil before removing or adding a coil diode. Both the size and number of wire turns have to match before this type of coil substitution can be done.
In electromechanical games (EM), each relay or game mechanism coil gets it's power from the appropriate voltage tap on the main transformer. This power is routed though a combination of leaf, score cam and relay switches to one side of the coil to be activated. The other coil wire lug connects to a common wire usually connected directly or indirectly through relay or score cam leaf switches to a "0" or center tap terminal on the transformer's secondary winding  (This "common wire"  connects one side of many coils to the same tap on the transformer).
A "common" wire can be used to de-energies banks of relays and/or multiple solenoid mechanisms at the same time.  For example; the "common" wire can be used to switch off all playfield solenoid coils or remove power from all flipper coils.
The "Tilt" relay uses a common wire disconnect in the event the game is tilted. During a "tilt" all flipper coils and/or all ball manipulation playfield mechanisms are disabled along with all scoring units.
Because multiple "common" wires can be used on the same transformer tap inside of a game, the tilt relay only interrupts the common wire to any mechanism that is "safe" to remove power from without trapping the ball on the playfield. Kickout holes, vertical up kicker and other mechanisms that require the game ball to drop into a hole are supplied with power during the tilt so they can operate normally to remove the game ball from the playfield. The "tilt" relay removes power to all scoring circuits so any activated playfield mechanism will not add to the total score for the player who tilted the game. Coil Voltage and Resistance Readings - Voltage measurements are affected by the method of measurement and the condition of the circuit (loaded or unloaded circuit, Peak versus RMS versus Average voltage readings). It is common place to indicate a standard supply voltage on a schematic when presenting a coil voltage (24 volts instead of 28 volts - 50 instead of 60 volts (60 volts=unloaded circuit voltage).
Coil Resistance measurements can also be affected by the method of measurement. Ohm meter lead resistance, accuracy of the meter, temperature of the coil wire, condition of the coil's wire lugs (corroded or clean), coil diode condition or non-conduction during resistance measurement.
Your readings in the real world may very slightly from what has been presented on this arcade coil charts page. All coil voltage and resistance readings listed are the average or most common voltage / resistance measurement.

Low Line Voltage Adjustment - Most Coin-Op Arcade games including both Electro-mechanical and electronic games have a way to increase the amount of voltage the power supply provides to compensate for low line voltage (This voltage is measured at the wall plug or voltage source receptacle). Usually a long distance between power transmission line transformers, an old fuse breaker, wiring corrosion and even different power line voltages between countries can cause a lowering of the power supply voltage. This condition can cause all of the game coils to appear to be weak or sluggish.  A low line voltage condition can even cause random game resets as describe on the Tech Tips page. Line Voltage should be checked before a game is turned on for the first time or when the game has been moved to a new location. It is always best to use a coil with a small wire gauge number (large diameter wire) and same number of wire turns as the original coil, but only if the exact part number cannot be found.
  For example; a 23-800 coil will have the same pull in strength as a 26-800 coil, however, the larger wire used in the 23-800 will take a longer time to heat up and therefore the coil should last longer without overheating. Coil body length, lug placement / length and coil sleeve type should always be considered when substituting coil part numbers. Usually the original coil part number can be purchased new. A coil part number substitution should only be considered when a new replacement coil is not available.
Pinball game coils have been specifically designed to operate the mechanism they are installed in. If a coil is no longer available and two potential substitute coils are manufactured then install the coil with the lower wire gauge number and the same wire turns number. This rule assumes there is no difference in the construction of the original and the substitution coils except for their wire diameter. For additional information on coils see the Coil Body Differences by coil manufacturer section on this page and our Tech Tips and the Arcade Game Tech Tips pages.

Gottlieb is always the exception to any industrial coin operated game coil or part number scheme.  Their coil part numbers do not provide any useful information and usually start with the letter "A".
A substitute for Gottlieb coils can be found by matching a known good Gottlieb coil's ohmage with the ohmage of a Bally coil or by matching a typical coil function.

Solenoid coil sleeve, coil magnet and flipper bushing  information.

Other pinball game and coin-op arcade technical info can be found on Pinball Medic's Tech Tips page.

Pinball Type Abbreviations:
EM = Electromechanical (score reels, relays)   SS = Solid State (digital score displays, chips (integrated circuits))
VUK=Vertical Up Kicker   G. P.=General Purpose Application

The charts below show solenoid coil numbers and typical application. They do not indicate Pinball Medic's current solenoid coil inventory.
Pinball Medic Amusements does not have any Atari or Zaccaria pinball coils and will not repair these brands of pinball.