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 Williams 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.
A standard sized Gottlieb or Bally coil body is 1 1/2 inches long (uses a 1 5/8 inch long coil sleeve). Williams used a 1 5/8 inch length coil body (with a 1 3/4 inches long coil sleeve). Replace a Gottlieb coil with a Bally manufactured substitution coil only if a genuine Gottlieb coil is unavailable.

 A Coil Stop is the metal bracket located usually at the base or 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 (see coil stop examples in the photo to the left).
 Special purpose coil stops let the coil's plunger travel through them to allow for a greater travel distance. For example, a bell or knocker solenoid has a coil stop with a hole in the center of it.  The longer the distance a plunger moves the more force it will have at the end of its travel and the louder the noise it will cause when the plunger strikes a bell, chime or other sound device.
 Bell and knocker units usually require a coil sleeve with an extended base like the Williams/Bally Reference Part Number 03-7067-3 and are sometimes longer then a stock sleeve.

 Vast differences exist between coil stops used by pinball manufacturers. These differences include stop bracket height, width and mounting hole spacing. We will add coil stop info to this page soon.

 Coil stops can become magnetized by the coil's magnetic field. This situation is the third most likely cause of slow to operate or stuck/jammed solenoid plunger problems. The Number one reason is dirt and then coil overheating resulting in a melted plastic coil sleeve and a bad coil.

 Flipper coil stops are very prone to "magnetizing and mushrooming" caused by the strong magnetic field strength of the flipper coil windings. A magnetized coil stop can cause a solenoid to be sluggish, slow to operate or to become stuck at the end of the solenoid plunger core's travel. The only sure way to solve a problem with magnetized or mushroomed coil stops is with replacement.

 Bally, for a short period of time in the 70's and early 80's, used a cheap coil stop with mounting holes too close together and used too thin of a metal to make the stop. These issues caused mounting holes in the coil stop brackets to crack between them. A broken coil stop can destroy the coil by allowing it to either fall off the mechanism and overheat or become misaligned with its plunger core causing excessive wear, loss of power and sometimes noise. No aftermarket part manufacturer seems to make this often broken part. The only replacement available is a completely new mechanism (flippers are very prone to coil stop breakage) with a stronger made coil stop installed.
 NOTE:  Pinball Medic has had to start upgrading whole flipper units by replacing the old mechanism with a complete new flipper unit and mounting bracket. These new flipper units are expensive (more then $50 each), however, provide a path way to rebuild the flipper in the future as coil stops can be found for these new mechanisms, but not for the original Bally/Stern flipper units.

 In the early days, Gottlieb tended to use a wrap around coil stop on its strongest coils (coil stop is shown in the photo on the left). Other pinball manufacturers tended to use the common ninety degree angled bracket with only two mounting screws. The Gottlieb wrap around coil stop incorporates stronger mounting using four screws and doesn't tend to bend or break apart.
 Damage can occur to all coil stop types after long periods of use. They often have "mushroomed" front surfaces due to the impact of the plunger or solenoid core and are in need of replacement. Flipper coil stops take the most abuse and should be checked often.

 Note on Gottlieb pinball replacement parts: New or NOS Gottlieb solenoid parts are usually much harder to find then the more common Williams stops. Gottlieb has forbidden any aftermarket company from remaking their unique game parts. No one can legally download a copy of a Gottlieb game manual, schematic, side art, game PROM image or even a parts catalog.  This is making Gottlieb pinball games difficult to repair or restore. This situation will eventually cause Gottlieb games to become non-repairable as soon as the limited stock of NOS parts are depleted and when no one can find any information on Gottlieb manufactured games. There is currently only one authorized Gottlieb parts dealer in the USA!
 NOTE: Williams chose to sell all of their pinball part designs to a small Austrian company that never produce very many replacement parts or replacement playfields. Bally and Williams parts designs have lately been resold to a new pinball parts manufacturing company in the U.S. It is yet to be determined if this new company will remake many of the rare and hard to find coils and other pinball parts so desperately needed by pinball hobbyist and coin-op repair shops around the world.
 Metal or Copper coil sleeves should be replaced with plastic sleeves, if they can be removed. A plastic coil sleeve will operate for a longer time and provide an improved performance.
 Solenoids are designed to operate without any lubrication. Application of any type of OIL or Grease is NOT recommended and can cause jamming or in some cases grease/plastic FIRES!!
 No type of coil sleeve, plastic or metal, ever require ANY FORM of OIL or any other type of lubrication.
 See our Tech Tip pages for more information on why not to use any lubrication on plastic pinball parts and what type of oil to use on motor oiling felt pads and leg level adjusters.
 A thin, round and made of 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 or vibrating when activated.
 These "spacers" can often be found on Gottlieb or Bally pinball games to allow for a Data East or Williams coil substitution and for other erroneous reasons. This is not a legitimate use for this spring steel spacer. Leaving out the ring spacer during legitimate coil substitution can cause the coil to vibrate and make a loud noise every time the coil is activated.

 Coil part number suffix or prefix (suffix=numbers or letters following a coil part number) - AE-23-800 - 04) and letter or number coil suffix / prefix (SA3-23-850DC) indicate the following coil modifications:  coil sleeve type used (metal or plastic sleeve and length), coil diode polarity and position (top or bottom of wire lugs), wire lug placement, length of the wire lug at the base of the coil or the length of the mounting insulator or coil base.
 Bally or 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.

Wire Gauge, Number of Wire Turns and Coil Strength Rules

 The higher the American Wire Gauge number, the smaller the diameter of wire. A small diameter wire has more resistance per foot of wire then a large diameter wire 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. Small sized wires 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 two digits in the Williams 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.
  American wire gauge/size information

 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 Strengths, Turns of Wire Rule and Coil Power Supply Voltages

 Coil pull in strength wiring rule:  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.

 The coil's wire diameter does not effect coil strength to any effective degree. Large diameter wires will not heat up as fast as a small diameter wire (This assumes the same amount of current is flowing through the two different wire sizes with the same amount of total coil resistance.) Large sized wires are used in coils that are to be activated many times during game play and/or for strong coils like the power stroke winding on flipper coils. Pop bumpers, sling shots and chime coils are all examples of mechanisms that typically use a coil with a low wire gauge number (large diameter wire).
 Long energized relays (coin lock-out, lock relays) use another wiring method to keep from overheating. Typically they are wound with small diameter wire and use many turns of wire. This produces a physically small coil size and very high resistance relay coil (low relay coil pull in strength). High coil resistance provides little current flow and less heat inside the relay's core.   Wire size information

 Raising the power supply voltage was also used over the years to increase the strength of solenoid coils in arcade games (This is not the same as high tapping a game.). An increase in voltage gives 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 of a coil. High coil supply voltages (greater then 24volts) can also 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 because of Ohm's Law.
 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 and the same number of wire turns. Also, DC coils can be driven by transistors (instead of relays) that use no moving parts, as long as a coil diode (reverse polarity biased) is provided to absorb the 'kickback' of the coil. DC can simplify the driver circuitry used in electronic pinball games and provide stronger solenoids.

 When some early EM pinball games were made, AC to DC current conversion was both rare and expensive to do. Current conversion was eventually made cheap and easy with semiconductors inside of a bridge rectifier. However, the early expense of current conversion started the tradition of not converting AC into DC that lasted all the way to to the start of electronic pinball games.
 There were a very few old table top or wood rail pinball games powered with a battery. No AC to DC conversion was needed and the whole game was powered with battery supplied DC current.

 This tradition or trend is one reason why very few electromechanical pinball game was ever made with all direct current powered coils. Game designers would rather spend a lot of time trying to engineer AC relays that don't hum then to convert a whole game to DC.  Everyone had to wait till electronic games forced the use of DC to power everything to get the coil strength and ease of design benefits that direct current provides.

 Weaker coils (large number of turns of wire, Example a relay coil with 6000 turns of wire) can withstand longer activation times without overheating because of the many turns of wire that has to be used and the higher coil wire resistance. Many turns of wire produces a coil with lots of resistance that limits current flow and hence decreases the heat inside of a coil.
 Pinball solenoid coils are never activated for more then about a quarter to half of a second during normal game play. Unless they were designed to be activated for a very long time like "coin lock out" or "hold" relay coils (Electromechanical (EM) pinball coils are activated for a much longer time when compared to electronic pinball games). 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 play field switch on an EM pinball) usually have at least 1300 or more turns of a large diameter wire. Score reel, chime, 'lock' relay, coin lockout coils and the 'hold' relay coil on most EM pinball games 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 or too strong replacement coils can also over burden already stressed coil drive electronics shorting their life spans.
 "High Tapping" a game with a normal line voltage is not recommended either 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 Arcade Tech Tips page for more info on high tapping the game's transformer. Or our coin-op catastrophe collection for some interesting coil photos.

Flipper Coils, Drive Circuits and Coil Supply Voltages and Current Types
Additional Data East and Saga flipper coil information is on our pinball circuit board charts

 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. The flipper coil "hold" coil does have to be able to be activated permanently without burning up the coil. This is why a lot of turns of wire are used on the "hold upright" coil on a flipper 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 28-39 voltage solenoid coils.
 Use Caution: Anything over 48 volts is considered dangerous by an electrician. Wear rubber gloves if you are not comfortable when working around 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 of a voltage.
 Players could receive painful shocks if the game was not properly grounded either by the missing 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 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 electromechanical ages of pinball. Electronic pinball game coils were usually all powered by DC current (transistor driven coils).
 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.
  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 a substitute AC coil to make it compatible with direct current (DC) 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 supply wire can be used to de-energies banks of relays and/or multiple solenoid mechanisms at the same time.  For example; the "Tilt" relay uses a relay to disconnect the supply wire to a bank of relays and playfield parts in the event the game is tilted. During a "tilt" all flipper coils and/or all ball manipulation playfield mechanisms not needed to remove the ball from the playfield are disabled along with all scoring units.
 Because multiple "supply 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 Voltages by Game Manufacturer
Gottlieb 1947 to 1989: 28 volts, Gottlieb 1989 (system3) to 1996: 50 volts
Williams 1947 to 1963: 50 volts, Williams 1963 to 1986: 28 volts, Williams 1986 to 1989: 28 or 50 volts, Williams 1989 to 1999: 50 volts
Bally 1947 to 1977: 50 volts, Bally 1977 to 1988: 43 volts, Bally 1988 to 1999: 50 volts
Zaccaria: 39 volts

Coil voltage information is from a R.G.P. post and has not been 100% verified.

 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 the measured 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 bias during the 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 (Line 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.

Coil Part Number Substitutions

 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. However, specs like core length, coil diode (if present on original coil) and coil body style should always be the same between the original coil and its substitute coil.
  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. Therefore, the coil should last longer without overheating assuming there is not a fault with the coil's driver suppling continuous current to the coil. 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 were 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
on  Arcade Game Tech Tips or on our Forum pages.

   Pinball Type and Chart Abbreviations:
  EM = Electromechanical (score reels, relays).
  SS = Solid State or Electronic (digital score displays, chips (integrated circuits)).
 NOS = New Old Stock. An old part that has never been used on a game.
 VUK=Vertical Up Kicker   G. P. = General Purpose Application
  EOS = End of Stroke Switch used on most flipper units (usually a leaf type of switch).

 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.