Common Flipper Troubleshooting
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This page discusses flippers. When flippers don't work, the game isn't fun.
Flippers are a solenoid, like any other pinball solenoid, with two changes in detail. First, unlike most solenoids, they rotate in place instead of moving something linearly, which is what solenoids are really good at. Second, flippers are under the player's control. They get used a lot, and they tend to work themselves to falling apart.
1 Principle of Operation
Most games manufactured since the 1980's are either using Williams parts or parts that are very similar to Williams parts. This is particularly the case for Data East/Sega/Stern. In any case, the principles are the same for all flippers.
[PHOTO] A flipper has a few key parts: there's the bat, above the playfield, that interacts with the ball. This connects via a shaft to the mechanism under the playfield.
[PHOTO] A solenoid coil under the playfield is energized when the player pushes the flipper button. This coil pulls in a plunger, which in turn is attached to some mechanism. In this case, there's a link and a pawl. The pawl grips the shaft, and that rotates the flipper. When energized, a coil stop prevents the plunger from moving too far. When the flipper is in its most-energized position, a end-of-stroke switch opens to step the coil down from the high-power "kick" side to the low power "hold" side.
2 Variations
Variations abound. These are discussed on the relevant pages for that pinball system. But common variations include:
- parallel-wound coils, like those on late '80s and newer Williams games, and Stern SPIKE™ games. These have two diodes on the coil.
- serial-wound coils, used on EM games, early solid state Williams and all other solid state games. These have only one diode.
- single-wound coils, like those on later Data East, Sega, and Stern games prior to 2015 titles. These singly-wound solenoids do not have a hold winding. These can have one diode or no diode.
In addition to the above, there are two differently controlled flipper assemblies.
- mechanical flippers (non-CPU controlled), which are enabled by a relay
- solid state flippers, like Williams' Fliptronic flippers, Data East games using a solid state flipper board, and computer controlled Sega and Stern games. These all use logic for end-of-stroke detection and handling.
Mechanically, these are all still fairly similar. A solenoid activates, pulls in a plunger, and cranks the flipper up. Still, the mechanisms can look quite different and may require different tools.
2.1 Mechanical Verisons
Manufacturers tended to keep the same flipper mechanisms for long periods of time, but there are variations. (See Stern's service bulletin 152.) This may mean parts have slightly different performance and tolerances, and sometimes the manufacturers were not particularly communicative. For instance, Williams changed their flipper plungers to be a little shorter around the Pinball 2000 time frame, but didn't document it well.
These are discussed further in each of the various solid-state systems' pages.
2.2 Coil Differences
All manufacturers had a few different flipper coil types so they could dial in the flipper strength. Stronger coils make ramp shots easier and kill drop targets without mercy. Weaker coils make the game more challenging and/or frustrating, and ramp shots become more difficult or unbelievably impossible.
The manual typically indicates the correct coil.
For some EM games, Pinball Resource sells "yellow dot" and "orange dot" souped-up coils to give the flippers more power. These are a popular option that may make the game more fun.
2.3 Two-stage
Some games with more than two flippers have a double "two-stage" flipper button. Hold it all the way in and both flippers fire. Hold it halfway in and only the lower flipper fires. This is quite common on Williams and later (System 3) Gottlieb games.
(This is distinct from the power being switched below.)
Two-stage power switches must be filed as they are high-current switches and do arc. Two-stage solid-state switches must not be filed. Filing or burnishing a solid state flipper cabinet switch will destroy it in short order.
2.4 Power switched by flipper
Some games with more than two flippers have a button that activates both flippers, but power for the upper flipper is activated by the lower flipper being upright. This chain happens with a "lane change" style switch in addition to the EOS switch. This is somewhat common on Bally games, but Black Knight 2000 also has this.
Chained power switches must be filed as they are high-current switches and do arc.
2.5 Lane Change
Many games (1980 Firepower and later) have a "Lane Change" feature where activating a flipper cycles lights, enters initials, etc. On later games (mid '80s and later) this was accomplished with solid-state circuitry, but on earlier games it was accomplished with an extra stacked switch on the flipper itself, or on the flipper cabinet switch (see games such as Williams Taxi). All of the manufacturers used this scheme at some time.
"Lane change" switches must be cleaned (not filed).
3 When Things Don't Work
3.1 Weak flipper
Almost anything can cause a weak flipper, including
- Wear in the link
- Worn or dirty sleeve
- Worn coil stop or plunger
- Poor solder connections on flipper coil
- EOS switch opening prematurely
- Dirty / broken flipper coil sleeve
- Flipper too low to playfield
If the flippers have not been rebuilt, suspect they are worn out or dirty first, and rebuild. Particularly for Williams 50V flippers, this is usally the problem.
3.2 Won't flip
- Fouled, broken, or open EOS switch
- Fouled or pitted cabinet switches
- Flipper relay not enabling
- Poor connections on circuit board which houses flipper relay
- Broken coil wire
- Solenoid voltage could be missing, the flipper fuse could be blown
- Flipper button could be dirty
3.3 Machine guns
Press the button, the flipper goes up, then drops down, then goes up again, etc. See Broken coil wire.
3.4 Flipper sticks up
If the flipper goes up, but won't go down, cut the power to the game. If the flipper stays up, something is binding. If the flipper goes down, something was holding it up electrically.
4 Common Problems
4.1 Wear in the link
Particularly a problem in Williams and Stern mechanisms, but a possibility in every flipper mechanism, the link is the weaker piece of plastic between the plunger and the pawl. Since it's the softest piece of the mechanism, it is guaranteed to go bad first.
Williams and Stern links have a bushing around the screw or pin that connects the plunger to the link. This is required.
The easiest thing to do in this case is to replace the whole crank assembly. These are readily available and highly recommended.
4.2 Worn coil stop or plunger
On every flip, the plunger moves into the solenoid and is stopped by the coil stop. Each flip does a little bit of damage. Eventually, the plunger and coil stop will distort into a mushroom shape. The plunger will drag in the sleeve, losing power.
The easiest thing to do in this case is to replace the whole crank assembly. These are readily available and highly recommended. Alternatively, the coil stop and plunger can be filed back into their original shapes. This helps, but it takes away even more material.
4.3 Worn or dirty coil sleeve
The plunger and coil stop play themselves to death and give off little bits of metal and dirt. These get deposited in the coil sleeve, which is worn away on every stroke.
If you have a coil sleeve apart, replace it. If a sleeve doesn't go into the coil freely, it's probably time to replace the coil. See Baked coil.
Very old flippers may still have brass sleeves. It is generally recommended to replace these wth nylon.
Never lubricate flipper mechanisms.
4.4 Baked coil
Flipper coils aren't usually the immediate problem, but they do go bad. If a new coil sleeve does not freely slide into and out of the coil when disassembled, the coil is baked and can be replaced.
4.5 End of Stroke Switch (EOS) Misadjusted
A normally closed, non-solid state end-of-stroke switch should open only at the end of the flipper's stroke, about a total of XXX travel. If it opens sooner, it sacrifices power. If it opens too late, or not at all, the coil will be damaged.
Note that on games with solid-state flipper control, it is not likely to damage the coil with a mis-adjusted EOS switch, but the game will not play quite as well.
4.6 End of Stroke switch pitted
Note that on games with solid-state flipper control, end-of-stroke switches are typically normally open and should not be filed. Just clean them with a business card.
4.7 Broken coil wire
A flipper coil must be a continuous coil of wire. If it isn't, the flipper won't flip. The break is usually near the lug, in which case it can be soldered back on after the enamel is stripped off the wire. Or, just put in a new coil.
4.8 Missing diode
Most (not all) flippers have one or two diodes on the flipper coil:
- New Stern SAM games have none
- Williams games after about 1988 have two
- Bally games after about 1989 have two
- EM games have none (the exceptions are Gottlieb games starting with Cleopatra and newer)
Check the manual if uncertain. (Checking the other flippers in the game may not be good enough because flipper coils do get changed.)
The diodes are used to "snub" a back-EMF voltage. When an energized solenoid is turned off, it has a bunch of residual magnetic force that wants to go somewhere. The coil diode dissipates that stored energy and burns it off. Otherwise, it will find a more dangerous place to go and may crash the computer or harm the drive transistor.
The symptoms from a missing diode can vary wildly:
- Game resets (Twilight Zone, WPC)
- Flipper won't stay up (Simpsons Pinball Party, Stern White Star)
- Nothing (High Speed, Williams System 11)
4.9 Wrong Angle
It's important to have the flipper at the expected rest angle. Otherwise, some shots will be difficult or impossible.
For example, on a Gottlieb Monte Carlo, the flippers were adjusted to be to "high" or "flat". This made the shot to the left orbit too weak, which made it impossible to lock the ball in the top saucer. Since that is requied to get multiball, the game was not much fun. (Fixing this made the game slightly fun, about what a Monte Carlo is when it's operating correctly.)
On a Williams game, the factory correct angle for a flipper can be set easily. Under each flipper is a roll pin hole. Put a toothpick in that hole. The flipper bat, wrapped in its rubber ring, should just rest on the toothpick.
4.10 Flipper too low to playfield
Other than Gottlieb "fat boy" flippers, flipper bats are held down to the playfield because they sit on the playfield bushing. It's just gravity. If the playfield bushing is worn, the flipper will drag on the playfield. This will rob power, but worse, it will take the paint off of the playfield.
The flipper should never drag on the playfield. Williams included a tool with their games to get the flipper gap right, but that tool usually gets lost. This tool has been reproduced and is available from Marco Specialities.
If the flipper is dragging on the playfield, replace the flipper bushing. This means taking the flipper bracket off under the playfield, removing three screws and their nuts, putting the new part in, and reassembling. Make certain to remove the nuts on the backside of the flipper plate. If the nuts are not first removed, sheering of the flipper bushing screws is high.
4.11 Flipper too high off playfield
A flipper can be set too high off the playfield as well as too low. With the Williams-style mechanism, a flipper that is too high will mean that the plunger has to move in two directions, up as well as in. This will sacrifice flipper power.
4.12 Wrong rubber ring on flipper bat
Every flipper bat is designed to take a particular rubber ring. Usually it's hard to put the wrong one on, but Gottlieb flippers take a skinnier, 3/8" wide ring. This nests neatly in the groove on the flipper.
Other modern flippers (Bally, Capcom, Data East, Sega, Stern, Williams) use a 1/2" rubber ring.
If a 1/2" ring is used on a Gottlieb flipper, it will either cause airballs or for the ball to be driven into the playfield. Either will cause playfield wear.
4.13 Stripped mounting holes
Most flippers mount to a base plate that is slightly offset from the playfield. By screwing everything to a metal plate, it tends to hang together better. Older EM-style flippers don't do this, and it's one of the reasons they aren't as strong.
Sometimes, the screw holes strip. To fix this, you can try any of the following:
- glued dowel in the hole trick
- go from #6 to #8 screws; this may mean enlarging the holes in the base plate's feet
- make all new mounting holes, rotating the flipper slightly so it has new wood to work with
Not every trick may work in any given situation.
Note that both Williams and Bally went to larger #8 hardware in the late '80s because extra flipper power was overwhelming the original hardware.
4.14 Damaged bat
Flipper bats break. Sometimes it's obvious from the top, but sometimes, it's only visible from underneath. It's really common on the one-piece bats (Williams/Stern style) to find out that some of the reinforcing of the bats has broken. It's worth replacing these because it reduces flipper power.
The solution is to replace the bat. Usually the logo can be matched, but at some point Williams turned the "W" on the flipper over.
If the plastic shoe is a separate screwed-on piece from the metal bat underneath (Gottlieb "fat boy" flippers, some Bally flippers, older Williams flippers, early "classic" Stern flippers), these can naturally be replaced separately.
4.15 Bad contact on flipper button switch
On traditional (not solid state) flippers, if hitting the button doesn't activate the flipper but jumping the contacts does, the contact needs to be filed. This is a high-current switch with tungsten contacts.
The contact must be present. After many years, these switches do fall apart, and this will eventually make them unreliable.
4.16 Dirty flipper button opto or button
On games with solid-state (electronically controlled) flippers, a dirty flipper button can also cause the flipper not to work.
Particularly on Williams' Fliptronic games, the flipper buttons are controlled with an opto-activated button. These get dirty after years of use, and optos can have more exotic problems. See the WPC page for more information.
4.17 Blown fuse
Last but not least, maybe it's just a fuse. All games have a fuse for the solenoids, but many games have a separate fuse for flippers. Both must be good. Do not over-fuse and do not bypass a fuse.
5 Parts Availability
Parts availability for the major manufacturers is quite good. Even fairly obscure parts (the short Bally/Williams "Thing Flips" flipper) are now available again!
Parts may not be available for other manufacturers. (Add your recommendations here.)
6 Sharing Parts Between Different Manufactuers
In general, parts are not compatible between manufacturers.
Williams tapered links fit Stern flippers. They're much cheaper. Otherwise, the Stern parts are subtly incompatible with the Williams parts. Williams rounded links will not fit Stern games. The rounded links are thicker, and will drag within the Stern flipper pawls.
Some collectors replace Gottlieb and Stern mechanisms with Williams mechanisms. For the price of a Stern rebuild kit, you can get a whole Williams flipper. The Gottlieb System 3 flippers are even more expensive. This is a matter of taste as well as being cheap.