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If your pinball machine keeps resetting, start with power delivery before you blame the CPU board. In most cases the problem is a voltage drop, a bad connector, or a tired part in the power path. The fastest safe order is simple: check the wall outlet, check the power-supply test points, check the CPU-board 5V under load, and then inspect connectors and headers.

That order matters because a machine can read fine at idle and still reset the moment flippers, bumpers, or multiball add load. A basic multimeter can miss brief dips that happen only for a split second, so a “good” reading on the bench does not always mean the machine is healthy in play.

If you are also trying to decide whether the machine is worth the repair bill, it helps to compare the problem against pinball machine values and pinball machine prices before buying parts. Older games can be very fixable, but some are harder to keep running than people expect, especially once connector work and board repair enter the picture.

What a pinball reset usually means

A reset is when the machine suddenly reboots in the middle of play or at startup. Sometimes it happens randomly. Other times it only happens when the game is under load, such as when flippers fire, a kicker hits, or multiple solenoids activate at once.

That pattern is the big clue. In many older solid-state games, resets are caused by the 5V logic rail dipping low enough to trip the watchdog or CPU. In hobby repair discussions for WPC games, people often look for roughly 4.92V to 5.1V at the board and treat anything near 4.7V at the CPU as a serious warning sign. That number is not universal for every pinball machine, but it explains why a game may seem fine until action starts.

Community repair threads also keep pointing to the same troubleshooting order: wall voltage first, then power-board test points, then CPU-board voltage, then connectors. A long-running Arcade-Museum repair thread for WPC games follows that exact logic, and it is still the most practical place to start.

Quick checks to do first

Before you pull boards or order parts, run through these low-risk checks.

Try a different outlet. Use a wall outlet on a known-good circuit if you can. Low line voltage or a loose receptacle can trigger resets.
Inspect the power cord and inlet. Look for frayed insulation, heat damage, loose plugs, or a wobbly IEC inlet on newer games.
Look for burned connectors. Darkened plastic, browned pins, or a connector that feels loose is a real clue, not cosmetic damage.
Note when the reset happens. If it only happens when flippers fire, think voltage sag, connector resistance, or a coil diode issue. If it happens at startup, look harder at the power switch box, fuse holder, thermistor, and inlet wiring.
Check whether reseating helped only briefly. Temporary improvement usually means the fault path is real, but the connector or header still needs proper repair.

Reset symptom checklist

What you see	Most likely area	Best first move
Resets when flippers or bumpers fire	5V sag, connector resistance, coil diode noise	Measure 5V under load and inspect coil diodes and connectors
Resets randomly after warming up	Weak caps, heat-sensitive headers, regulator path	Check power-board test points and heat-discolored parts
Resets at startup or as soon as you power on	Power switch box, inlet, fuse holder, thermistor	Inspect the mains side and the switch box carefully
Resets stop after reseating a connector, then come back	Poor contact, oxidized pins, cracked solder joint	Repin the connector and replace the header pins

Step-by-step diagnosis, from safest to most advanced

Measure the wall outlet. In North America, the machine should see roughly household mains voltage at the outlet. If the line voltage is low or the receptacle is loose, fix the house-side issue first.
Check the power cord and power switch box. The original article’s warning about the power switch box was on the right track: bad connections in the fuse holder, a failing thermistor, or a worn power switch can absolutely cause trouble. If the cord connection is loose or heat-damaged, stop and repair that before going deeper.
Probe the power-supply test points. On a game that resets under load, you want to know what the 5V rail is doing on the supply board itself and then at the CPU. A meter that looks fine at idle may still miss brief dips during play.
Reproduce the reset on purpose. If the machine resets every time a flipper fires or a certain coil activates, you have a strong lead. That usually points to a load-related sag or a noisy coil circuit rather than random logic failure.
Inspect and test connectors. Pull and inspect only after you have notes on what changed. If reseating the connector temporarily fixes the problem, that is not the end of the repair; it means the connector path is bad enough to need repinning, new crimp terminals, or header replacement.
Check the bridge rectifier, filter caps, and regulator parts. These are common failure points on older solid-state games. If one of them is weak, the machine may run but still reset under load.

Common causes by board family

Not every pinball machine fails for the same reason. The age and board family matter.

WPC and WPC-S games

Williams and Bally WPC games are classic reset candidates because the 5V rail is so important to the CPU. If the voltage dips, the watchdog can reset the game. The usual trouble spots are:

bridge rectifier and filter-cap path on the power board
burned or loose connectors between the power supply, driver board, and CPU board
tired header pins that look fine but no longer grip the connector well
load-related sag when flippers or other solenoids fire

If a WPC game resets during flipper action, do not just replug the connectors and call it done. That may prove the fault path, but the real fix is to repin the harness and replace heat-stressed headers.

System 11 games

For System 11 machines, a lot of hobby repair advice starts with the +5 filter cap and the connector set, then moves to the +12 section. The 2N6057 transistor and its socket are also worth checking if the game is unstable. Corrosion or poor contact at that socket can create symptoms that look like broader board failure.

In practice, System 11 resets often come from the same basic issues as WPC resets: tired caps, resistance in the wiring, and parts that fail only when the machine is loaded. If the game looks fine until something big happens on the playfield, think power first.

Older Bally and Stern solid-state games

Older Bally and Stern machines from the late 1970s and early 1980s are famous for burned connectors, dirty pins, and weak chip sockets. On those games, the MPU board and driver board should be inspected carefully. If the socketed chips have intermittent contact, the machine may reboot, go dead, or behave unpredictably.

Also keep in mind that not every symptom that looks like a reset is actually a reset. On some older games, a switch-matrix fault or a bad switch capacitor can mimic a reset-like problem, especially if a particular pop bumper or start switch is involved. That is why it pays to observe exactly what the machine does rather than assuming every glitch is the same.

When reseating is a clue, not a cure

A lot of people get fooled here. If you unplug and reseat a connector and the game runs again, that does not mean the problem is fixed. It usually means the connector was making just enough contact to get by.

The real repair is more permanent:

repin the harness with fresh terminals
replace heat-damaged header pins on the board
replace burnt connector housings
repair any cracked solder joints around heavy connectors or power parts

This is also why replacement boards are not a cure-all. A new board can still act flaky if the harness, transformer-side connectors, or inlet wiring are old and oxidized. Several community reports describe a temporary improvement after reseating, followed by the same reset problem returning until the connectors were actually repaired.

When to repair and when to step back

If the machine is valuable, complete, or hard to replace, repair usually makes sense. If the cabinet, playfield, or board set is rough and the machine still needs connector work plus power-supply repair, the total cost can climb fast. That is where checking the game’s condition against pinball machine values and repair costs can keep you from throwing money at a project that does not make sense.

Older games also demand more maintenance than newer owners expect. If you are still deciding whether a classic table fits your skill level, our pinball maintenance breakdown explains what usually needs attention over time.

When to call a technician

Stop and bring in a pinball tech if any of these apply:

the mains wiring or power switch box looks damaged
you find scorched connectors or melted housings
the machine has low line voltage in your home and you are not comfortable checking the circuit safely
you need board-level solder work but do not already do that kind of repair
the game still resets after the obvious connector and power checks

There is no prize for forcing a repair when the fault is already beyond basic troubleshooting. A good technician can often diagnose the exact failure path much faster than swapping parts at random.

Frequently asked questions

Why does my pinball machine reset when the flippers fire?

That usually points to voltage sag or resistance in the power path. The flippers pull a lot of current, so a weak connector, tired capacitor, bad bridge rectifier, or noisy coil diode can push the 5V rail low enough to trigger a reset.

Can a multimeter miss the problem?

Yes. A standard meter may show normal voltage at idle and still miss very short drops during play. If the game only resets under load, you need to measure at the right test points while the machine is acting up.

Is reseating a connector a real fix?

Usually not. Reseating is useful because it proves the connector path is part of the problem, but the lasting fix is repinning the harness and replacing worn header pins or damaged connector housings.

What should I check first on a WPC game?

Check the wall voltage, then the power-supply test points, then the CPU-board 5V, then the connectors and header pins. On many WPC and WPC-S games, that order saves a lot of guesswork.

Could it be something other than power?

Yes. On some older games, switch-matrix issues or a bad switch capacitor can look like a reset problem. That is less common than power-delivery trouble, but it is worth keeping in mind if the symptoms do not match a normal voltage-drop pattern.

Pinball resets are frustrating, but they are usually diagnosable if you follow the power path in order. Start at the outlet, move to the power board, check the CPU voltage under load, and do not trust a quick connector reseat as the final answer unless the connector and header have actually been repaired.

Pinball Machine Resetting? Here’s How to Fix It