Pinball Flipper Rebuilding – How to Fix and Replace

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 Components

Flipper kit parts
Parts Contained in a Typical Kit.

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
4) Spring
5) Coil sleeve

Spring on Plunger
Spring inserted on plunger. Note that the larger turns go toward the coil.
Flipper Spring
Flipper Spring
Torsion Spring
Torsion Spring – curtesy of Marco
Playfield bushing.

Optional (usually not included in the kit) – the bushing.

An extensive list of game / manufacturer specific parts are on this page.

Two Different Types

flipper button switch.
Full power flipper switch. Note the damage.
Fliptronics flipper switch
Low Power Flipper switch.  Note it looks new. NEVER FILE.

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.

When Should I Rebuild A Flipper?

Signs of flipper wear.
Flipper that open to different amounts.

Signs that a flipper rebuild is due are:

* When open, one moves further than the other.
* They are not aligned when at rest (this is usually a simple adjustment).
* They are sluggish or lack power.
* A flipper sticks and stays in that position when the power is turned off.
* You just purchased a used pinball machine and the previous owner cannot tell you when they were last rebuilt.

Left and right flipper linkage.

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.

flipper button switch.
Worn full power flipper button.
EOS switch
EOS switch where the full power travels through the switch.

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. The coil has very low resistance, 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 in 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.

Worn flipper switch of the type that could be filed with a flexstone to improve performance. Filing or replacing these contacts are as important as the EOS switches.

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.

Mechanical Checks:

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.

Electrical Problems:

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.

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.

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.

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:

EOS switch
EOS switch where the full power travels through the switch.

3) Jumper the EOS switch with 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 stronger, it is your EOS switch. Can clean the switch with alcohol or file. Most likely replace. If no change, then the EOS switch is good.

4) Remove the jumper on the EOS switch. Lift up the playfield. Take a clip lead and connect it to one side of the flipper switch. Quickly jumper 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.

5) It could be the power supply to the flipper. Check for burnt connectors where the flipper circuit plugs into the power supply board.

Flipper Diodes

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 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.

Coil and diode.
Coil with diode.  Diode symbol on the left.

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).

Coil and diodes
Coil and diodes. Note the bands on the diodes.

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.

Rebuilding the Flippers

The easiest way to rebuild a flipper is to order a flipper repair kit from a pinball parts supplier.

Tools Needed

Allen Wrenches
Allen Wrenches
Suggested Tools. Nut drivers too.

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) Flexstone (for non-computer controlled)

Optional: Flipper gauge. Nice to have.  But making sure of a small amount of vertical movement is usually sufficient.


1992 And Newer Flippers

Fliptronics EOS
EOS switch normally open. Fliptronics (Williams).

Newer machines have EOS switches that are normally open, then close when the flipper is activated. These switches process low voltages and should never be filed. These are either gold or silver plated. Some other EOS switches on newer machines (like 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).

Fliptronics flipper switch
Low Power Flipper Buttons.

Note that this 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 is a flipper switch for an early fliptronics game such as The Addams Family.  Some fliptronics games used optical switches that do not have metal contacts.


How To Rebuild a Pinball Machine Flipper

Flipper parts
This is a typical setup in an EM or early SS pin.
(click on the photo for a larger image)

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 early full power EOS, 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.

Screws holding the flipper bat

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.

Socket wrench (or nut driver).
Remove coil stop.

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.

Crank held in place by spring.
Clean out bushing.

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.

Press out the coil sleeve.
New sleeve on the left.

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.

Worn linkage to the top right.  Not terrible, but worthwhile replacing.
Holding all the parts together. Spring not on plunger is added later.

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.

spring in plunger
Spring in plunger. Include that here.

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.

Washer / spring.
Attach the new coil stop.

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.

Use Allen wrench to tighten this style.

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:

Simple low voltage EOS switch used in Fliptronics. It is open when flipped is off.

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.

EOS Switch install
Soldering wires to EOS switch.

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.

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.

Alignment marker
Flipper alignment marker on the playfield.
Flipper alignment point
Flipper alignment point is below the flipper.

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.

Flipper closed
Flipper closed (off). EOS switch leafs must make contact.
Flipper partially activated
Flipper almost all the way up. EOS switch still closed.
Flipper open
Flipper all the way open. EOS switch must be open or the coil will burn up.
Fliptronics EOS switch.

Fliptronics EOS switch. Switch is open when the flipper is at rest. Closes when the flipper is fired.

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).


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