Common Flipper Troubleshooting

Note: This page is a work in progress. Please help get it to a completed state by adding any useful information to it.

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:

• computer-controlled flippers, like those on recent Stern games. These singly-wound solenoids do not have a hold winding.
• parallel-wound coils, like those on late '80s Williams games. These have two diodes on the coil and the wiring is slightly different.
• solid state flippers, like Williams' Fliptronic flippers those on most Data East games. These 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.

3 When Things Don't Work

3.1 Weak flipper

Almost anything can cause a weak flipper, including

• Wear in the link
• Worn coil stop or plunger
• Flipper too low to playfield

If you have not rebuilt the flippers, suspect they are worn out or dirty first, and rebuild.

3.2 Won't flip

See #Broken coil wire. Or, the game's solenoid voltage could be missing, the flipper fuse could be blown, or the 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.

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 mis-adjusted

An end-of-stroke 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

Check your manual if you're not sure. (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.

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.