Pinball Score Display Not Working: Is It the Display or the Power Supply?

The machine boots, the flippers work — and the scores are blank. Or one player display is dark while the other three are fine. Or every digit is there but so faint you can only read it in a dark room.

Before you spend a few hundred on replacement displays, do one measurement. The display itself is often innocent.

The short version: if all the displays are dead, suspect the display power supply and check its voltage at the test points for your system. If one display is dead and the others work, it is that display or its connector. If one segment is missing, it is usually the display tube. If everything is uniformly dim on a Gottlieb, that is how its fluorescent displays age.

Contents

• Start with the pattern, not the multimeter
• Know which kind of display you have
• A word about the voltages
• All displays dead: measure the display voltage
• One display dead, the rest fine
• A single missing segment
• Everything dim (mostly a Gottlieb story)
• When the CPU board is the real problem
• Should you just fit LED displays?
• FAQ
• Sources

Start with the pattern, not the multimeter

The chain is short: the power supply makes the display voltage, the CPU board decides what each digit shows, and the display turns that into light. Which link to suspect depends on the pattern.

What you see	Most likely area
Every display blank, game otherwise runs	Display power supply / high-voltage section
One display blank, others normal	That display, or its connector
Same segment missing on one display	The display tube itself
Same digit position dead on all displays	CPU board digit-strobe circuit
Everything readable but faint	Ageing displays, or low display voltage
Nonsense characters, flickering	Connectors, grounds, or the CPU board

Know which kind of display you have

This trips up owners who move between brands, because the three big manufacturers of the era did not use the same display technology.

Gottlieb used vacuum fluorescent displays — VFDs: small vacuum tubes with a heated filament, a grid and segment anodes, glowing soft blue-white, which is why Gottlieb fitted coloured filters over them (blue as standard, green on machines such as Haunted House). The tubes came from suppliers including Futaba and NEC, and a segment lights at roughly 40 to 60 volts.

Bally, Stern and Williams used gas-discharge displays — the Panaplex type, usually just called plasma. Cold-cathode neon devices with no filament, glowing the familiar orange, needing closer to 100 volts and up to strike a segment.

So the same symptom means different things. "Dim" is a classic ageing VFD on a Gottlieb; on a Williams it usually means the high voltage has drooped.

A word about the voltages

Display supplies are the most dangerous thing in an otherwise forgiving backbox. On a Bally or Williams the display rail runs well over 100 volts DC, and on some Bally boards over 200 — enough to hurt you badly. Work with one hand where you can, and treat the large filter capacitors as live even after switch-off. If that makes you uncomfortable, this is a reasonable job to hand to someone else.

All displays dead: measure the display voltage

If the game boots, the flippers fire and the sound plays, the CPU is alive. Blank displays across the board then point at the supply that feeds them.

Gottlieb System 80, 80A and 80B

The System 80 power supply board carries the display rails, nominally 60 V and 42 V. Owners report these collapsing to a few volts, at which point the displays go very faint or vanish, and the high-voltage section of that board is where to look. (The same applies across the range, whether you have System 80's 6-digit displays or System 80B's single alphanumeric one.)

Before condemning anything, though, note the single most useful thing in this article: on System 80 the 60 V and 42 V rails sit on a different ground from the 5 V and 12 V logic supplies. Put your black probe on logic ground and your red probe on the 60 V test point, and you can read zero on a perfectly healthy board. The black lead belongs on the ground pin in the same connector as the rail you are measuring. A good number of "dead power supply" posts turn out to be exactly this — and grounding on System 80 repays understanding generally, as our ground mods guide explains.

Williams System 3 to 7

Williams needs +100 V and −100 V DC, measured at connector 3J5: pin 4 for the positive rail, pin 3 for the negative. Anywhere from +90 to +105 and −90 to −105 is healthy, and the test points are the same across System 3–6 and System 7.

When these rails are wrong, a single component swap rarely holds. Each half of the circuit has two transistors and a set of diodes, and experienced techs advise replacing all the major components in that section rather than hunting one part — the zener diodes especially are prone to failure. If the CPU LED is also odd, cross-check our System 7 diagnostic codes guide.

Bally and Stern, 1977–1985

Identify your board before trusting any number, because the display supply lives in different places across the range: a rectifier board in the backbox (the "-18"), or a board in the cabinet (the "-49" and "-54" types).

On the AS-2518-18 rectifier board, PinWiki gives roughly 150 to 180 V DC regulated at TP2, with TP4 carrying the unregulated supply at around 220 V ±25 V. Other repair guides quote nearer 200 to 250 V on the voltage regulator / solenoid board. Both can be right — different test points on different boards. Find your revision and measure the point your manual names. Two parts on early Bally boards are notorious for age-related failure while you are in there: the LM323 5 V regulator, and the electrolytic capacitor at C23.

One display dead, the rest fine

Good news: the lit displays prove the supply. Now it is that display, its connector or its wiring. Power off, then:

1. Reseat the connector. Forty-year-old pins oxidise and lose tension. This alone fixes a surprising number of dead displays.
2. Look at the pins. Burnt, browned or pushed-back pins are common, and so are wires a previous owner re-pinned into the wrong position — a miswired connector produces missing digits that look exactly like a dead display.
3. Swap it with a known-good display. If the fault follows the display, it is the display; if it stays with the position, it is the wiring or the board.

That swap costs nothing and answers the question outright. Do it before ordering anything.

A single missing segment

If one display always fails to form certain numbers — a 1 that shows as nothing, an 8 that reads as a 9 — note which digits fail and work out which segment they share. A segment dead on one display but fine on the others is almost always the display tube itself.

The exception: if the same segment or digit position is missing on every display at once, that is a shared signal — the CPU board's segment or digit drive circuit, not the displays.

Everything dim (mostly a Gottlieb story)

A uniformly faint Gottlieb display is often not a fault at all — it is a VFD that has done forty years of service. Check the 60 V and 42 V rails first, because low display voltage looks identical.

If the rails are good and the display is still weak, there is a well-known rejuvenation trick among Gottlieb owners. Flippers.com documents it as 12 V DC to the leftmost display pin and ground to the rightmost for 7 to 12 seconds, the filament wires glowing red and warming, repeated about once a year — and warns that 4-digit displays take a maximum of 8 V, not 12.

Be careful: you are deliberately overdriving a filament, the margin between reviving it and destroying it is not huge, and results vary. If the display is rare, weigh that up first.

When the CPU board is the real problem

Board faults do show up as display faults — but rarely only as display faults. If the scores are wrong and the game also resets, loses its settings or stalls during boot, read the board's own diagnostics first: our guides to Bally MPU LED flashes and to what each board actually does will tell you more in five minutes than an hour of poking at displays, and our no-boot diagnostic covers a machine that will not start at all.

Scrambled or flickering digits are more often a cracked solder joint on the display header pins than a failed chip — the tell-tale sign is behaviour that changes when you flex the board gently. And check for battery damage: on Gottlieb System 80 and 80B the backup battery sits on the CPU board, and leaking electrolyte creeps along traces and under chips, as our guide to stopping battery corrosion shows.

If the high-voltage section has failed and the rest of the board is equally tired, replacing it can beat rebuilding a forty-year-old supply component by component: the BallyDri power and driver board for Bally and Stern, the WillFA7 for Williams System 3 to 7, or the GottFA80_Plus, which replaces CPU, driver and power supply on Gottlieb. We test boards before they ship and support them afterwards.

But a new board will not fix a dead display tube, a miswired connector or a mis-measured test point — which is exactly why the measurement comes first.

Should you just fit LED displays?

LED replacements exist for most machines of this era and are a legitimate choice: brighter, no high voltage, no ageing filament. Two honest caveats. The look changes, which matters to a collector keeping a machine original. And if you fit them on an early Bally, the standard advice is to remove the display high-voltage fuse, since that voltage is no longer needed and leaving it live is an unnecessary hazard.

Our own view: fix the supply first and find out whether your original displays were ever faulty. A great many are not. Keep the originals either way.

FAQ

Why are all my pinball displays blank but the game still works?

Almost always the display power supply, not the displays. If the game plays, the CPU is alive — so measure the display voltage at your system's test points before buying anything.

What voltage should a Gottlieb System 80 display be?

Nominally 60 V and 42 V. Measure against the ground pin in the same connector, not against logic ground, or you will read zero on a healthy board.

What is the display voltage on a Williams System 3 to 7?

+100 V and −100 V DC, at 3J5 pin 4 and pin 3. Anywhere from +90 to +105 and −90 to −105 is acceptable.

Why is one pinball display dead and the others fine?

The working displays prove the supply, so it is that display, its connector or its wiring. Reseat the connector, check for burnt or miswired pins, then swap the display into a known-good position.

Can I fix a dim Gottlieb display?

Sometimes. Check the 60 V and 42 V rails first, since low voltage looks the same. Gottlieb's fluorescent displays also dim with age, and owners use a filament rejuvenation trick — but it means overdriving the filament, so think twice on a rare display.

Are pinball display voltages dangerous?

Yes. Bally and Williams display rails run from around 100 V to over 200 V DC, and the filter capacitors stay charged after switch-off. Work with one hand, or hand the job to someone experienced.

Sources

• Home Pinball Repair: Early Williams SS machines
• Home Pinball Repair: Early Bally and Stern machines
• Pinside: Bally AS-2518-18 rectifier board TP2 voltage
• Pinside: System 80 — no displays, low 60 V and 42 V
• Pinside: System 80 power board, no 60 V / 42 V — the separate-ground trap.
• Flipprojets: VFD display technology
• Boston Pinball Company: Gottlieb display information
• Flippers.com: Gottlieb System 80 tips — the rejuvenation procedure and the 8 V limit.
• Wikipedia: Segment display

Not sure what your multimeter is telling you? Send us the machine and the readings — our technical support is free, before and after any purchase, including when the answer is a two-euro connector pin.