Coils & Coil Assemblies

Reels for Pinball Machines – The Heart of Numerous Game Features

Reels are among the most important electromechanical components of a pinball machine. They ensure that electrical energy is converted into precise mechanical motion, thereby forming the basis for numerous game features. Whether it’s flipper fingers, pop bumpers, slingshots, kickouts, ball ejectors, or other mechanisms—wherever something moves during gameplay, coils are almost always involved.

During a single game, many pinball coils are activated hundreds or even thousands of times. They must operate reliably within a very short time and consistently generate the same force. This high level of stress makes solenoids classic wear-and-tear parts that, over the years, can lose performance or fail completely due to aging, thermal stress, or intensive use.

Typical signs of a worn-out or defective solenoid include flippers with little force, pop bumpers with reduced impact force, or kickouts that no longer reliably eject the ball. However, the cause is not always exclusively the coil itself. Worn sleeves, defective microswitches, faulty end-of-stroke switches, damaged cables, or problems with the control board can also cause similar symptoms. Therefore, systematic troubleshooting is always recommended before replacement.

Different coils are used depending on the manufacturer and pinball machine model. They differ, among other things, in terms of their winding, electrical resistance, design, and intended use. For this reason, a replacement coil should always be selected to match the specific pinball machine. The right combination of coil, coil sleeve, and associated components ensures that all game functions operate reliably and that the original feel of the game is preserved.

At PU parts, you’ll find high-quality coils and coil assemblies for numerous pinball machines from Williams, Bally, Stern Pinball, Data East, Sega, Gottlieb, Jersey Jack Pinball, and other manufacturers. Whether you’re replacing a single coil, restoring a pinball machine, or overhauling an entire assembly—with the right replacement parts, you’ll lay the foundation for a reliable and long-lasting repair.

Why do mechanics in pinball machines wear out in the first place?

Coils are designed for continuous operation in a pinball machine and achieve a remarkable service life under normal use. Nevertheless, they are among the components that are subjected to enormous stress during every game. Each activation generates a magnetic field that moves a metal core, thereby triggering a mechanical game function. This process repeats—depending on the game element—often thousands of times and leads to natural wear and tear over time.

It is not only the coil itself that wears out. Often, adjacent components such as coil sleeves, plungers, stops, or return springs show signs of wear due to friction and mechanical stress. If these components are not inspected regularly, this can also affect the coil’s function and lead to reduced performance.

Another factor is heat generation. Every time the solenoid is activated, current flows through its windings and generates heat. Especially with intensively used game features or pinball machines in commercial settings, this strain accumulates over many years. Aging insulation, damaged windings, or solenoids that are constantly overloaded can eventually cause the magnetic force to weaken or the solenoid to fail completely.

In many cases, however, a coil is not the actual cause of a problem. If a coil remains permanently energized or is activated more frequently than intended, the cause may be, for example, a defective microswitch, a faulty end-of-stroke switch in older pinball machines, or a faulty control circuit on the circuit board. Therefore, when troubleshooting, it is advisable to always consider the entire interaction of the affected assembly and not just the solenoid itself.

If solenoids and their associated components are inspected regularly and worn parts are replaced in a timely manner, the reliability of many game functions can be maintained in the long term. At the same time, consequential damage is prevented, and the pinball machine remains reliably playable even with frequent use.

How can you tell if a coil in a pinball machine is defective?

A defective or worn-out coil does not always immediately manifest itself as a complete failure. Often, the pinball machine’s behavior changes only gradually at first. Individual game functions respond more sluggishly than usual, flipper fingers lose power, or the ball is no longer ejected reliably. Precisely because many fault patterns look similar, it’s worth conducting a systematic inspection of the entire assembly before replacing the solenoid prematurely.

A typical sign is a flipper finger that no longer generates its usual striking force or responds with a delay after being activated. Pop bumpers, slingshots, and kickouts may also function only partially if the coil’s magnetic force weakens or adjacent components are worn out. In such cases, one should examine not only the coil itself but also the coil sleeve, the plunger, as well as switches and mechanical guides.

A visual inspection often reveals initial signs of a problem. Discolored coil bodies, scorched windings, or a distinctly noticeable burning odor can indicate thermal overload. Loose connection wires or damaged solder joints should also be checked, as they too can lead to malfunctions.

Another indication may be unusual heat generation. While many coils do heat up during normal gameplay—especially in heavily used game features—if they become unusually hot within a short time or remain continuously energized, the cause should be identified as quickly as possible. Often, the problem lies not with the coil itself, but with a faulty control circuit or a switch that fails to open or close properly.

💡 Good to know:

A defective coil is often not the actual cause of a malfunction. Worn coil sleeves, stiff plungers, defective microswitches, or control issues can cause nearly identical symptoms. Therefore, it’s advisable to always inspect the entire assembly during a repair rather than simply replacing the coil.

Last but not least, it’s also worth paying attention to how the machine feels to play. Experienced pinball players often notice after just a few games if a game function is behaving differently than usual. It’s precisely these small changes that are often the first signs that maintenance or the replacement of individual components may be necessary. Taking action early on often prevents more serious consequential damage and maintains the reliability of your pinball machine in the long term.

Choosing the Right Coil for Your Pinball Machine

At first glance, many coils look very similar. In reality, however, they differ in numerous technical details that are crucial for reliable operation. Even minor variations in design, winding, or electrical properties can cause a game feature to no longer function as intended or place unnecessary strain on components.

For this reason, a replacement coil should never be selected based solely on its external appearance. Rather, the technical specifications and compatibility with the specific pinball machine are what matter most. Manufacturers such as Williams, Bally, Stern Pinball, Sega, Data East, Gottlieb, and Jersey Jack Pinball use different coils for various applications, depending on the model.

A reliable point of reference is the part number printed on the coil. This often allows for unambiguous identification and makes it easier to select a suitable replacement part. If the number is no longer legible or the coil has already been replaced in the past, service manuals, parts lists, or the Internet Pinball Database (IPDB) can often help identify the coil that was originally installed.

Equally important is the coil’s intended use. Pinball coils, pop-bumper coils, kickout coils, or coils for diverters and other assemblies differ in terms of their function and technical design. Therefore, you should always use a coil that is specifically intended for that function.

🔧 Workshop Tip:

Take a photo of the existing coil before removing it and note down the part number printed on it. Especially during extensive repairs or restorations, this makes reassembly easier later on and helps you clearly identify the correct replacement coil.

By carefully selecting the right coil, you lay the foundation for a reliable repair and ensure that your pinball machine operates again with the intended power, speed, and precision.

Why the Coil Sleeve and Plunger Should Not Be Overlooked During Repairs

When troubleshooting, attention often focuses first on the coil. In reality, however, a coil assembly consists of several components that only ensure reliable operation when working together. The coil sleeve and the plunger, in particular, play a crucial role but are often overlooked during maintenance work.

The coil sleeve serves as a guide for the plunger and ensures that it can move within the coil with as little friction as possible. However, signs of wear can develop as operating time increases. Deposits, material fatigue, or a damaged sleeve increase resistance and impair the plunger’s mobility. As a result, even a technically sound coil can lose performance.

The plunger itself is also subject to continuous stress. Over time, the many thousands of movements cause signs of wear on the contact surfaces or the surface itself. Depending on the application, these changes can cause play mechanisms to react more slowly or no longer generate their original force.

Especially with older pinball machines, it is therefore advisable to inspect the entire assembly rather than simply replacing the coil. If the coil, coil sleeve, and plunger are inspected together, it is often possible to identify which components are actually worn out during a maintenance session.

🔧 Workshop Tip:

When installing a new coil, it’s worth taking a close look at the coil sleeve. If it is discolored, damaged, or shows clear signs of wear, it’s recommended to replace it at the same time. This allows the new coil to perform at its full potential and prevents unnecessary wear.

A carefully maintained coil assembly plays a crucial role in ensuring that flipper fingers, pop bumpers, slingshots, and other game features operate precisely and that the game’s feel is preserved over the long term.

Quality and the right choice are key to a reliable repair

Coils play a central role in a pinball machine and ensure that numerous game features operate precisely and reliably. However, for a repair to be successful in the long term, it’s not enough to simply select the right replacement coil. It’s equally important to include adjacent components—such as coil sleeves, plungers, switches, or connectors—in the maintenance process and to regularly check their condition.

With high-quality replacement parts and careful troubleshooting, many problems can be permanently resolved, and unnecessary consequential damage can be avoided. Especially with older pinball machines, a systematic inspection of the entire assembly is worthwhile to preserve the original function and the familiar feel of the game over the long term.

At PU parts, you’ll find high-quality coils and coil assemblies for numerous pinball machines from various manufacturers. Thanks to detailed product information and our constantly growing knowledge base, we aim to help you find the right replacement parts for the maintenance, repair, and restoration of your pinball machine.

Frequently Asked Questions About Pinball Machine Coils