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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.   
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 (for pre-1992 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.

Flipper Components

flipper kit

 (click on the photo for a larger image)

 Flipper Parts -
Contained in a Typical Kit

1) Coil Stop                      
2) Crank Assembly
    a - Plunger
    b - Link
    c - Crank Arm
3) EOS Switch
4) Spring

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.

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) 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.

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 below of  The Addams Family contacts for an example of a 'newer' design 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.
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 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.

Rebuilding the Flippers

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

Tools Needed

1) Screwdriver (Phillips)
2) Allen Wrenches
3) Needle Nose Pliers
4) Wire Cutters
5) Soldering Iron & Solder
6) Nut Drivers

Allen Wrenches

Tools needed for flipper repair

When Should I Rebuild A Flipper?

Signs that a flipper rebuild is due are:

* One or more stick in the up position.
* When open, one moves further than the other.
* They are not aligned when at rest (this could be a simple adjustment).
* They are sluggish or lack power.

flippers open at different positions
These two flippers are both on and open to different angles. This could be due to worn links, or a previous owner that installed two different style of flipper mechanisms.

worn link
Worn link at the top. Click for larger image.

Determining if there is a lack of power is difficult to determine. As flippers wear out, they lose power slowly. As a regular user, it is difficult to notice a gradual loss of power. A quick test is to pull and push on both metal pieces to see how much play is in the linkage, then compare to a new one.

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.

While it is possible to just replace the Crank Assembly or even just the link. But the investment in the entire kit is usually well worth it.

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 do not 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.

           EOS Switch
EOS switch where the full power travels through the switch. Note it is closed when the flipper is not in use. This type switch wears out quickly and should be replaced. Careful observation indicates wear and burn where the two sides make contact.

flipper switch
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.

1992 And Newer Flippers

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).

EOS switch fliptronics
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. Only low current flows through these switches. They should never be filed. These switches can last longer than the linkage.
Fliptronics flipper switch
This is a flipper switch for an early fliptronics game such as The Addams Family. Only low voltage flows through this switch and it should never be filed. Later fliptronics games used optical switches that do not have metal contacts.

As a general rule of thumb, when I obtain a pinball machine, I expect to rebuild the flippers, unless the previous owner specifies that the pinball machine has been restored and specifically mentions that the flippers have been rebuilt.

                          How To Rebuild a Pinball Machine Flipper

flipper components early SS and EM


This is a typical setup in an EM or early SS pin.

1) EOS switch (and, lane change switch combination)
2) Diode (SS pins only)
3) Coil
4) Coil spring
5) Crank Assembly
6) Nut / screw for tightening flipper bat shaft
7) Flipper coil stop (partially hidden in photo)
8) Solenoid Bracket

(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.


Caution: Insure the machine is turned off and unplugged.

1) Remove the flipper by loosening the nut holding the flipper bat shaft (see item #6 above). 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.
2) Remove the flipper coil stop (#7 in the above photo). 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) At this point, the crank assembly is held in place only by the spring. Use your needle nose pliers to disconnect the spring from the base.
5) Use this opportunity to clean out the bushing hole for the flipper shaft. I use several q-tips or a towel and small amounts of isopropyl alcohol.

Williams Pinball Flipper
click on the picture for a larger image
Williams Fliptronic Flippers
Williams Fliptronics - EOS switch is open
1) Coil Stop   2) Diodes   3) Coil   4) Spring
5) Crank Assembly  6) EOS switch
7) Bolt holding flipper bat shaft

6) Inspect the diodes on the coil. 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.
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 assembly). Here is the only tricky part - insert the crank assembly through the solenoid bracket removed in step #2, then into the coil (diode / wire end towards the crank assembly like in the photo to the left, if possible). Hold all three parts together and insert the coil into the new coil stop from step #4.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.
11) If the spring is like that to the left, attach 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 voltage switch made of tungsten
b) Complex high voltage switch (like that to the right) 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, then closed in the Williams / Bally Fliptronics pins. In other pins, like Stern, EOS switches are low voltage, but start out closed.

12) Note the orientation of the EOS switch, which side faces the coil. 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, like the one to the right, 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.

Linear pinball flipper Bally
  Linear Style - Bally Flipper
1) Coil stop  2) Diodes  3) Coil  4) Spring  6) EOS switch with
c) lane change or upper flipper switch  7) Crank Assembly a) Plunger  b) Nylon bushing
Linear flippers were used by Bally for only a short period of time. The nylon bushing wears out quickly.  These flippers can be converted to the earlier flipper mechanisms. Contact your parts supplier for information as to what to order for your pin.

Stern Flipper
Stern Flipper Mechanism (from 2002)
1) Coil Stop  2) Wire connections (no diode)  3) Coil
4) Spring  5) Crank Assembly  6) EOS switch (broken)
7) Allen bolt to tighten the flipper shaft
8) Shaft to flipper bat

Tightening the Flipper Bat

At this point, the flipper bat shaft should be firmly connected to the crank assembly in step #8. Check its position in the playfield. It should be possible to swing the flipper bat into various positions. The flipper bat shaft is item #8 in the photo to the left.

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 #1.
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 possible, insert a toothpick into the marker and set the bat against the toothpick. 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 shown to the left. Some people will crank those so hard, that the two pieces bend and touch each other - don't do that.
18) Crucial: Check the EOS switch adjustment. For pre-1992 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.
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.

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