Flipper Repair Introduction
Of the machinery in a pinball machine, the flippers may get the most use and therefore wear and tear. Therefore, the flippers may need more maintenance than any other part of a pinball machine.
Cautions: Must read before proceeding. Machine must be turned off and unplugged.
A glossary of terms used on this page.
Note: Click on any image or links for a larger image.
How a Flipper Works (Pre-1992)
In order to diagnose a flipper problem, it is important to understand how a flipper works. By far, the best description is by Steve Kulpa, and there is no reason for me to repeat it here. If this is too complex for you, a simple version for pre-1992 flippers goes as:
1) Player presses a button that closes a switch to complete the circuit
2) The high power portion of the coil is energized
3) The coil creates a magnetic field, drawing the plunger into the coil, hitting the coil stop
4) The flipper opens, opening the EOS switch (most designs)
5) The EOS switch inserts the lower power coil into the circuit, reducing the power and current draw
6) When the player lets go of the flipper switch, the spring retracts the flipper, removing the plunger from the coil
7) The loss of power changes the coil into a power generator. The collapsing magnetic field creates electricity. For SS (solid state) machines, a diode shorts out this power, preventing damage to the circuitry.
Note: EM pinball machines that have DC solenoids also have diodes on the coil.
Flipper Parts – Contained in a Typical Kit from a parts supplier.
1) Coil Stop
2) Crank Assembly
– a – Plunger
– b – Link
– c – Crank Arm
3) EOS Switch
5) Coil sleeve
* – Flipper Playfield Bushing.
Optional (usually not included in the kit) – the bushing.
An extensive list of game / manufacturer specific parts are on this page.
Included is a description of different coil stops and sleeves.
Two Different Types
Pinball flippers worked the same way from the dawn of flipper pinball until the 1990’s. Prior to this change, full power went through every flipper switch and those switches burned out quickly which led to weak flippers.
About 1990, Data East / Sega (which became Stern), converted to computer controlled solid state flippers. Bally / Williams introduced Fliptronics about 1992 which also used low voltage and computer control. Sometimes, both these systems are referred to as Fliptronics, but that is a Bally / Williams term. The big difference between these two systems is the way we deal with their switches. The rest is the same.
For more information, see the page on Sold State Flippers – Fliptronics vs. DE/Sega/Stern.
When Should I Rebuild A Flipper?
Signs that a flipper rebuild is due are:
* They are sluggish or lack power.
* A flipper sticks and stays in that position when the power is turned off.
* When open, one moves further than the other (sometimes wrong coil stop was installed on one flipper).
* They are not aligned when at rest (this is usually a simple adjustment).
* You just purchased a used pinball machine and the previous owner cannot tell you when they were last rebuilt.
As flippers wear out, they lose power slowly. As a regular user, it is difficult to notice a gradual loss of power.
What wears out is the linkage in the crank assembly, where the parts rotate. The holes should be round. With time, they become oval. That means, as the plunger comes into the coil, there is an extra distance that the plunger has to travel until the flipper rotates and that saps power.
Other components that can reduce power to the flippers are the flipper button switch and the EOS Switch. For games prior to (about) 1992, the full power has to go through these switches, so any wear and tear on those two switches can sap the power. The easiest thing to do is replace those switches. EOS switches come with flipper rebuild kits.
Flipper button switches are not included in kits and must be ordered separately. It maybe possible to file those switches to restore their effectiveness, but this requires a certain technique – many people destroy these switches than fix them by filing them. Filing or replacing these contacts are as important as the EOS switches.
Check to insure that the correct coil is installed (see your manual). Some previous owner may have just thrown in a coil they had handy. Too weak of a coil, and it will act like it needs a rebuild. Too strong and plastics may be broken.
Troubleshooting Flipper Issues
When a machine starts to have weak flippers, owners are quick to blame electrical problems. By far, the greatest cause of weak flippers are physical problems than can be easily diagnosed by those mechanically inclined.
Note: Never lubricate any flipper parts.
1) Turn the machine off and unplug.
2) Remove the playfield glass. Tilt the playfield up and lean it against the backglass. Be certain the playfield is secure and will not come crashing down.
3) Manually move the flipper back and forth. Listen for any rubbing. Be certain that the flipper does not rub the playfield. Pull up on the flipper. There should be a small amount of up / down movement.
4) Check for a broken or weak spring.
5) Check for wear on the Crank Assembly Link (see photo above). This is what usually wears out first. If the hole in the link has become elongated, replace the Crank Assembly or purchase a rebuild kit.
6) Plunger and/or coil stop become mushroomed. This can cause the flipper to stick open or not move freely.
7) If there is any doubt about the wear and tear of components including the Crank Assembly, springs, EOS switch, or Coil Stop, purchase and install a rebuild kit.
8) Inspect the EOS switch and flipper switch for pitting and wear.
Read and understand “how a flipper works“. A great deal of current flows through the flipper coil when it is first pressed and any electrical resistance will slow it down. If working on Fliptronics or DE/Sega/Stern computer controlled solid state flippers, read this page.
Understand what type of flipper system you have. Generally, games older than ~1992 have the full power going through the flipper EOS Switch and Flipper Switch. Those get worn and require filing or replacement. Newer flipper designs have low power going through those switches and they wear slowly and must never be filed – see photos at the beginning of this page for an example contacts that must never be filed.
1) Turn the power off. Hook up a DVM across the two leads on the coil, where the two wires come in from the wiring harness. Set the DVM to the lowest resistance setting. With the flipper at rest, the resistance should be ~ 4 – 5 ohms. Higher values generally indicate a worn EOS Switch or, more rarely, a damaged coil. [A lower value could indicate a shorted / failing coil, but this is less likely.]
Note that coils usually do not have to be replaced. When they do, it is because the flipper does not work at all. A bad coil rarely causes a flipper to be weak. Sometimes coils get overheated and fail. This is usually caused by a EOS switch that does not open when the flipper ‘flips’.
2) Touch the two leads of your DVM together. It should read nearly zero. This value is your zero value. Connect the leads across the EOS switch. It should read nearly zero. If not, file (older games only) or clean with isopropyl alcohol. For newer machines, this value does not have to be near zero.
The following tests are quite tricky, involve higher voltages and can cause damage if not properly completed. For qualified personnel only:
3) Jumper the EOS switch with heavy duty clip leads. Turn on the pin. Touch and immediately let go of the flipper switch. See if the flipper is stronger. Be careful not to hold the flipper button in since this jumper disables the EOS switch, sending full power through the coil. Holding the flipper switch in could cause a coil melt or a fuse to blow. Just a quick tap. If the flipper is stronger, the EOS switch is defective. Can try cleaning the switch with alcohol or file. Most likely replace.
If no change, then the EOS switch is good.
Remove the jumper on the EOS switch.
4) Lift up the playfield. Take a clip lead and connect it to one side of the flipper switch. Quickly touch across the flipper switch and immediately remove. Does the flipper seem stronger? If yes, file your flipper switch or replace it. If no, then it is not your flipper switch.
Note that doing this can cause quite an arc and scar the clip lead connector.
5) It could be the power supply to the flipper. Check for burnt connectors where the flipper circuit plugs into the power supply board or bad soldering. This is the least likely cause of weak flippers.
A diode conducts electricity in one direction only. It is there to protect the sensitive electronics in solid state (SS) pinball machines.
Why diodes? When DC flipper coils are activated, electricity runs through the coil. When the flipper is turned off, the magnetic field around the coil collapses and the coil turns into an electric generator and power runs in the opposite direction. The power generated by the coil can fry the electronic controls. The diodes conduct electricity one way and short out the collapsing field. Without those diodes, the circuit board will fail. If the coil is installed with the wires switched, those same diodes will conduct when the power is applied to the coil which should blow the fuse.
Electrical Mechanical (EM) flipper coils do not have diodes because they run on AC. The EXCEPTION is those later EM machines that run on DC (Ex: Captain Fantastic). DC machines have a bridge rectifier that converts the AC to DC. Without those diodes, that rectifier will fail.
When rebuilding the flippers, take the time to inspect the diodes. Put a little bit of stress on each one with a screwdriver. If they break apart, replace the diode. The diode marking must be in the same direction as the orginal diode (see photo below).
If replacing a coil, be sure to check the diodes on the coil to see if they are ‘pointing’ in the same direction. If they are, connect the wires to the new one in the same order. If the direction of the diodes are reversed, then reverse the wires.
The drawing above shows the symbols of a coil and a diode. A flipper coil would have two coils and two diodes. To the right is a flipper coil with its two diodes. Looking closely at the picture (click for larger photo) shows the bands on the bottom of each coil indicating direction of the diodes.
Note that most new coils come with a 1N4004 diode installed which is good to 400V. If replacing a broken diode, or installing a diode when one is missing, it is a good idea to install a 1N4007. It is rated for 1000V and costs almost exactly the same. Save those 1N4004 diodes for the switch and lamp matrix.
When replacing a diode, it is a good idea to remove the old one. Be certain to pull those diodes tight against the plastic body of the coil assembly. ‘Hanging in the air’ diodes are more likely to break.
Some games have the diode installed on the circuit boards in the backbox. That was done to reduce the breaking of diodes by the physical action of the solenoid, and because too many repair people were installing diodes backwards. Check your game to see if the diode belongs on the coil. Generally, if the old coil had a diode, the new one should also.
Rebuilding the Flippers
The easiest way to rebuild a flipper is to order a flipper repair kit from a pinball parts supplier.
1) Screwdriver (Phillips)
2) Allen Wrenches (some flippers)
3) Needle Nose Pliers
4) Wire Cutters
5) Soldering Iron & Solder
6) Nut Drivers and/or socket wrenches
7) Thin metal file and/or flexstone (optional)
Optional: Flipper gauge. Nice to have, especially when doing this the first time. But making sure of a small amount of vertical movement is usually sufficient.
1992 And Newer Flippers
Newer Bally / Williams machines have EOS switches that are normally open, then close when the flipper is activated. These switches process low power and should never be filed. These are either gold or silver plated. Some other EOS switches on newer machines (like Sega/DE/Stern) are normally closed, then open when the flipper is activated. These are also gold or silver plated and should never be filed. The EOS switches can be cleaned by inserting a business card and dragging it across the contacts as they are held closed by your fingers. Or they can be cleaned with Q-tips and a small amount of 91% isopropyl (not rubbing) alcohol (Note: flammable – see cautions).
Note (in the picture) that this low power EOS switch shows almost no wear. It belongs to a Williams / Bally Fliptronics pin. These are recognizable because the switches are open when the flipper is at rest. These switches can last longer than the linkage.
This (see photo) is a flipper switch for an early fliptronics game such as The Addams Family. Some fliptronics games used optical switches on the flipper buttons that do not have metal contacts.
How To Rebuild a Pinball Machine Flipper
Prior to beginning disassembly, pull up and down on the flipper itself. Notice that there is a small amount of vertical movement. When re-assembling, it is crucial that there be a little bit of up and down movement on the flipper bat, or the mechanism will bind and not swing freely.
The procedure for EM, early full power SS, Fliptronics and DE/Sega/Stern flippers is nearly identical. The only difference is the treatment of the switches. Never use anything abrasive on Fliptronics or low power DE/Sega/Stern flippers.
Steps: Caution: Insure the machine is turned off and unplugged.
1) Remove the flipper by loosening the nut holding the flipper bat shaft. Some flippers are held in place by two set screws and an Allen (hex) wrench is required. Others are held in place by a combination of a nut and an Allen bolt like the Williams assembly to the right. Some require only a socket wrench to loosen.
Note: At this point, it is possible to unsolder the two wires coming from the playfield wiring harness to the coil and remove the entire flipper assembly. This makes it much easier to rebuild the flippers. If doing so, take photos to insure that these two wires are soldered to the same tabs on the coil. Wiring backwoods will cause a short.
2) Remove the flipper coil stop (#1 in the above ‘Components‘). This may require a nut driver or allen wrenches.
3) At this point, the solenoid coil and crank assembly will no longer be held in place. Remove the coil from the plunger and let it hang by the wires.
4) Use your needle nose pliers to disconnect the spring from the base.
5) Clean out the bushing hole for the flipper shaft. I use several q-tips or a towel and small amounts of isopropyl alcohol. Some kits include a new bushing. Note, if the flipper dragged on the playfield, likely cause was this worn bushing. Replace it.
6) Inspect the diodes on the coil. Carefully insert a small screwdriver behind the diode and push slightly to see if it is broken. If one is broken or suspect, replace it. Note that some coils have two diodes, others just one and some do not have any at all.
7) Replace the coil sleeve. Check to see which end of the coil has the sleeve with the collar. Press out the sleeve from the other side, then insert the new one with the collar on the same side. It maybe impossible to remove some sleeves. That is usually because the coil overheated and is ruined. Replace the coil and use a new sleeve.
8) Note that in the kit, there is a left and right crank assembly. Compare the new ones with the one you have removed and select the identical one. Attach the new spring (to the plunger or to the tab, depending on your type of spring).
Note: Some flipper systems have the spring on the shaft. If yours does, be sure to insert it through the plunger. The larger loops go towards the coil.
Here is the only tricky part – insert the crank assembly through the solenoid bracket, (add spring now if like that to the left) then into the coil (diode / wire end towards the crank assembly, if possible).
Hold all three parts together and insert the coil into the new coil stop from step #2. While holding this all together, manipulate the crank assembly into its proper position so that it is ready to be connected to the flipper bat shaft. If this assembly had a spring on the plunger, be certain to install it prior to inserting the Crank Assembly into the coil.
9) If the original coil stop had a washer / spring attached, set it on the new one. Attach the new coil stop, removed in step #2, to the base plate. At this point, all components should be held into place.
10) Insert the flipper bat shaft through the playfield and into the crank assembly. Tighten the shaft so that it is secure and cannot fall out, but do not over tighten.
Pull up and down on the flipper bat. There should be a little up and down movement.
11) If spring is outside the plunger, attach it the other end to the bracket. Needle nose pliers make this step easier.
Replacing the EOS Switch – Soldering Iron Required
Types of EOS Switches:
a) Simple high current switch made of tungsten
b) Complex high voltage switch (see Bally linear flippers, above) which includes a lane change switch
c) Simple low voltage switch (usually ’92 and later).
Types a) and b) are closed when not in use. In b), the lane change part of the switch will be open.
Type c) will be open when the flipper is not in use (normally open) in the Williams / Bally Fliptronics pins. In other pins, like DE/Sega/Stern, EOS switches are low voltage, but are closed when the flipper is not in use (normally closed).
12) Note the orientation of the EOS switch, which side faces the coil and which leaf is hit by the flipper as it opens. Remove the screws holding the switch. Leave the old switch dangling by the wires.
13) Mount the new EOS switch in the same orientation as the old one. Tighten the screws firmly.
14) One at a time, unsolder the wires from the old switch and attach them in the same place on the new switch. If there are only two wires, location is not crucial. But if it is a multilevel switch, it is crucial that the wires be connected to the same tabs.
Make absolutely certain that none of the wires from the EOS switch are touching or shorting anything else. On many systems, these wires carry high voltage and can fry other components.
Many flippers starting around 1988 to 1992 (pre-solid state / Fliptronics) had parallel coils and had capacitors connected to the EOS switches. These capacitors were installed to reduce arcing and extend the life of the switches. Check your manual. If your coil has two diodes, with two wires going to one of the end tabs on the coil, and is not sold state / Fliptronics, then it is a parallel coil and requires the capacitor. In the above picture, the parallel coil is on the right with two wires going to the left tab.
The capacitor can be installed in either direction.
Tightening the Flipper Bat
At this point, the flipper bat shaft should be firmly, but not tightly, connected to the crank assembly in step #10. Check its position in the playfield. It should be possible to swing the flipper bat into various positions.
15) While holding the flipper mechanism in the closed (at rest – power off position) below the playfield, swing the flipper bat above the playfield. If the bat turns too freely, tighten the screws or bolts holding the shaft in place. If it is difficult to turn, loosen these screws or bolts just a little. Make certain that there is a little up and down movement as noted prior to step #10. Use the Flipper gauge if you have one.
16) Swing the bat into the desired position. If there are small markers in the playfield, the bat should either point at the marker, or rest on it. If the alignment point is below the flipper, insert a toothpick into the marker and set the bat against the toothpick (without the rubber). If no markers are present, set the bat parallel to the wire on the playfield.
17) Tighten the bolt / screws on the crank assembly. If after a few minutes of game play, the flipper bat starts to shift position, it was too loose.
It is possible to over tighten the type with a bolt. Some people will crank those so hard, that the two pieces bend and touch each other – don’t do that.
Adjusting the EOS Switch
18) Crucial: Check the EOS switch adjustment. For non-Fliptronics pins, the EOS switch must open when the flipper is activated (up). The EOS switch should open as late as possible so that full power goes to the flipper as long as possible. But the switch must open completely or the coil will burn and/or arcing will occur and ruin the EOS switch.
For Fliptronics EOS switch: switch is open when the flipper is at rest. Closes when the flipper is fired. Note that that this is the opposite of what happens with older style full power flippers.
For DE/Sega/Stern EOS switch: these flippers are also computer controlled, but the EOS is adjusted like an older style flipper. The EOS should be closed at rest. The EOS will open when the flipper is activated.
19) Rebuild the other flipper. When finished, the two flippers should sit at the same angle. Try playing the pin. Readjust the position of the flippers if they seem incorrect to you. I mark the date if flipper rebuilding with a sharpie on part of the metal (not the coil or plunger).
Update Fippers to The Best Style
Most owners rebuild the existing flipper mechanisms in their machines to the original specifications. However, earlier flipper mechanisms had their limitations.
WPC Style Flippers
If your pinball machine was built prior to 1989, chances are you have old style coils, poorly designed springs and weak EOS switches that burn out quickly. Flipper rebuild kits for 1975 to 1988 pins cost from $40 on up. However, WPC pre-Fliptronics kits for Bally / Williams pins cost only $20. After the initial installation, there is a 50% savings with each rebuild!
Or looking at it another way, you can spend $40 on a rebuild kit. Or $80 on a conversion to WPC and have a new coil and coil bracket, superior spring and EOS, then half-price rebuilds from then on.
Serial vs. Parallel Coils
If your coil has a single diode, then it is a serial coil. If it has two diodes, it could be serial or parallel. Parallel coils have two wires to the left lug. Series coils have two wires going to the center lug. Parallel coils used in non-Fliptronics pins must have a capacitor on the EOS switch.
Why Parallel Coils?
There is some evidence that EOS switches with a capacitor and parallel coils will last longer.
Why WPC Style?
Besides the cost of rebuilding, older style flippers have inferior springs. Many of them have springs on the flipper coil and plunger. Those springs break easier and tend to tear up the mechanism. WPC flippers have springs outside the flipper which last longer and make the flipper feel more snappy.
While wiring will go to the same lugs, what happens is a bit different. In older serial coils, the EOS switch shorts out the ‘hold’ coil. Opening the switch sends current through both the ‘power’ and ‘hold’ coils which drops the current / power.
In parallel coils, the EOS switch connects the current to the ‘power’ coil. Opening the EOS switch removes the current from the ‘power’ coil. The power is always traveling through the ‘hold’ coil. Since these two coils collapse at different times, two diodes are needed.
Downsides and Complications
This conversion works great for early Williams SS pins running at 28 volts, and early Bally pins running at 43 volts. This guide is not intended for Gottlieb pins. We do not have information about converting EM pins. DE/Sega non-solid state pins are not covered here. Sega / Stern pins with solid state (the flipper coil has only two lugs) cannot and should not be converted.
The flipper base on these style flippers is a bit larger than the area occupied by older flipper systems. Some of the old ones did not even use a plate. That can make locating this flipper plate difficult or impossible in some pins.
In other pins, the plate may have to be turned and located in a different direction. In that case, the wires may not reach the new location. When adding an extension to the wires:
- Use heavy gauge stranded wire.
- Insert shrink wrap tubing over one end of the wire.
- Twist the wires together tip to tip, so the wire looks like an extension.
- Solder the wires together.
- Slide the shrink wrap tubing over the patch and heat the tubing with a heat gun, (maybe) a hair dryer, or [?].
Converting Different SS Pinball Machines
The entire mechanism for early Williams and Bally SS pins will be replaced. Use the ordering information below.
If updating Williams System 9, 11 and early WPC flipper mechanisms with older style springs on the plunger, you already have the correct coils. It is possible to drill a hole in the EOS bracket to accept the spring, or order a new base plate, then install the spring, capacitor, and rebuild the flipper.
No conversion information is available for Gottlieb, EM, and DE/Sega/Stern pins. Sega Stern pins with solid state flippers are good as is.
The parts needed can be ordered on any pinball parts supplier. But the easiest is to order them from Pinball Life, where they have complete assemblies. Always look for WPC flipper mechanisms from ~1992, but with normally closed (NC) EOS switches. Normally open switches are for Fliptronics and those will not be used here.
Coil – Check your solenoid voltage. If converting an older Williams System 3 – 7 game, your solenoid voltage is 28 VDC, then select the SFL 19/400 – 30/750 coil. Early Bally / Stern SS pins had 43 VDC solenoids. This is not quite as high as the WPC pins that had 50 VDC, so slightly more powerful coils are used to compensate. If FL23/600 – 30/2600 use a FL11630. A FL24/600 – 30/2600 calls for a FL11722.
EOS Switch – From the drop down menu, select the 03-7811 normally closed EOS switch.
Coil Stop – We use A-12111. A comparison of coil stops.
Base Plate – Order a left plate and a right plate for each pair of flippers. If there are upper flippers, it will be important to specify whether that is left or right.
Capacitor – The kit does not come with a capacitor. Order one for each flipper and install it. You will need a cable tie to hold the cap to the bracket and/or double sided sticky tape (we usually skip the tape), and shrink wrap tubing to insulate the wires.
Flipper Bat – Don’t try to reuse the old one. Wear will make it difficult for the new mechanism to hold onto the shaft. A generic no logo one is fine, unless you really have to have that company logo.
The flipper assembly comes with flipper bushings, so no need to order separately.
How a Flipper Works – Steve Kulpa’s great explanation. [Steve’s website is down as of 2020. This is a link to the WayBackMachine website.
Parallel vs. Serial Coils – A group discussion on the differences between coils.
Copyright 2006 – 2020, all rights reserved.
Comments, including suggestions, improvements, errors, etc. are welcome (see below).
If you have a specific question about your game that does not directly apply to rebuilding flippers, please see our FAQ section.