Every generation of pinball machines has its own "well-known" faults. If you know which system you have, you know where to start. Here are the four systems we come across most often in Greece, with the faults that show up again and again.
The guides assume you have a multimeter, a soldering iron and the manual of the machine (see the FAQ, question 12). For the voltages of each system see the article Tools and measurements.
Williams System 3 to 7 (1977–1984)
Examples: Flash, Phoenix, Gorgar, Firepower, Blackout, Black Knight, Jungle Lord, Pharaoh, Time Fantasy.
How to recognise it: four boards in the backbox: MPU (CPU) top left, driver bottom left, power supply on the right with the big heatsink, sound top right. 6- or 7-digit displays. The transformer and the big blue capacitor are at the bottom of the backbox. You can see them all on the page Anatomy of a pinball machine.
The classic faults
- Connectors. The number one fault. The connectors between the power supply and the other boards, especially those of the +5 V and the GI lighting, burn and blacken. Symptom: resets, intermittent operation, half the lighting out. Cure: resolder (reflow) the pins on the boards and replace the female contacts (Molex/Trifurcon) of the burnt connectors. Don't just clean them, they will burn again.
- Power supply board. The bridge rectifier and the +5 V regulator age and the voltage drops. The high voltage for the displays (+100 and -100 V) is on the same board: when all the displays go out at once, start here.
- Driver board. The power transistors of the coils (darlingtons of the TIP/2N type, depending on the version, see the manual) short out and the coil stays locked on. The special solenoids (bumpers, slingshots) are driven directly by their switches and have their own group of transistors. Always check the diode on the coil as well.
- Batteries on the MPU. Three AA cells in a holder on the board. If they have leaked, the corrosion eats the traces and the pins of the chips around them. Clean with vinegar and water, a brush, and then conformal coating. Move the batteries to an external holder.
- MPU–driver ribbon cable. The 40-pin ribbon between the two boards oxidises. If the machine does strange things (wrong lamps, coils), unplug and reseat the ribbon or replace it.
- PIA 6821. The interface chips burn out when something shorts on the playfield. A whole group of lamps, coils or switches that doesn't work often ends up at a 6821.
- Displays. The gas plasma displays age. There are LED replacements that plug straight into their place.
What to keep in stock: fuses of all the ratings on the power supply board, bridge rectifiers, a few coil transistors, 1N4004 diodes for the coils, female connectors and pins, 6821s, a set of rubbers and sleeves.
Bally -17 and -35 (1977–1985)
Examples: Eight Ball, Playboy, Kiss, Paragon, Harlem Globetrotters, Xenon, Centaur, Eight Ball Deluxe, Fireball II. The AS-2518-17 board in the early ones, the -35 from 1979 onwards. The Stern machines of the same era (M-100, M-200) are essentially the same system.
How to recognise it: in the backbox the MPU with the NiCad battery on it, the rectifier board with the big fuses, the solenoid driver with the TO-3 transistors, the lamp driver with the rows of SCRs. 6- or 7-digit displays running on 190 V.
The classic faults
- The NiCad battery. The most destructive fault of this generation. The battery is soldered onto the MPU and leaks alkaline electrolyte that spreads under the chips. If you are buying a Bally, look at this first. Remove it, clean, check every trace in the area, and fit an external holder or a lithium battery with a diode.
- The 7 flashes. At power-up the LED on the MPU must flash 7 times and then go out. If it doesn't flash at all: +5 V isn't getting there, or the reset circuit. If it stops at the first or second flash: a problem in the RAM or the ROMs. The manual says what each number of flashes means, and this is the best diagnostic tool you have.
- The 5101 RAM. The CMOS RAM that holds the scores and settings with the battery. It fails often, especially after a leak. Symptom: the settings are lost, the game starts with odd credits, or doesn't start at all. Fit a socket before you put in a new one.
- Rectifier board. Its connectors burn, especially the GI one. The bridge rectifiers and the big 43 V capacitor of the coils age. Weak flippers and resets start here.
- Solenoid driver board. It has the +5 V regulator (which feeds all the logic) and the TO-3 transistors of the coils, e.g. 2N6284 on the power coils. The +5 V circuit (transistor, regulator, adjustment potentiometer) needs checking on every Bally that resets. The same board also generates the 190 V for the displays.
- Lamp driver board. The 2N5060 SCRs burn out one by one: a lamp that stays always on or always off. They are easy to replace.
- Displays. As with all gas plasma: they age. The LED replacements for Bally are among the most widely available.
What to keep in stock: 2N5060, 5101 RAM with socket, fuses, bridges, 1N4004 diodes, 2N6284 transistors (or equivalent) for the coils, female connectors.
Williams System 11 (1986–1990)
Examples: High Speed, Grand Lizard, Pin*Bot, F-14 Tomcat, Millionaire, Fire!, Cyclone, Taxi, Earthshaker, Black Knight 2000, Whirlwind, Diner, Dr. Dude. There are versions 11, 11A, 11B and 11C with small differences in the boards. The Data East machines of the same era are almost a copy.
How to recognise it: one big MPU that combines CPU and driver, a separate power supply board, a sound board with an amplifier, and from 11A onwards alphanumeric displays with 14 segments. Many of them also have a second small driver (auxiliary power driver) for the flash lamps.
The classic faults
- Burnt GI connectors on the power supply. The GI passes through the power supply board and its connectors burn so often that it is considered routine maintenance. If you see blackening on the plastic, replace the connector and the pins, and use Trifurcon-type pins.
- Reset / +5 V drop. As with all of them: bridge, capacitor, regulator and connectors of the power supply.
- Special solenoids. The transistors that drive the bumpers and slingshots short out often, because they work without control from the program. Symptom: a bumper that stays locked on or doesn't work, often together with a blown fuse.
- Batteries. Three AA cells on the MPU, right above sensitive chips. Same cure as on System 3-7.
- Flipper relay (11B and later). The flippers are enabled through a relay. If no flipper works at all, check the relay and its transistor before you go looking at the coils.
- Displays. The alphanumeric displays have more drivers than the old ones. Half a line out = a driver on the display board.
Williams / Bally WPC (1990–1999)
Examples: Funhouse, The Machine, Terminator 2, The Addams Family, Twilight Zone, Indiana Jones, Star Trek TNG, Theatre of Magic, Attack from Mars, Medieval Madness. Versions WPC, WPC-S, WPC-95. Dot matrix display (DMD) on all of them except the first two.
How to recognise it: CPU board, power driver board with lots of fuses and big capacitors, DMD controller, sound board, and on most of them Fliptronics for the flippers. On the WPC-95 the power supply and the DMD driver are on one board (AV board).
The classic faults
- Battery corrosion on the CPU. The three AA cells are at the top of the CPU and when they leak they destroy the area below them. Look at this first before you buy. Move them to an external holder or fit NVRAM.
- Burnt GI connectors on the power driver board. The GI lighting connectors (the J115 to J121 group, depending on the version) burn on almost every WPC. Reflow and connector replacement is mandatory maintenance.
- The WPC reset. The machine resets when many coils fire at once. Cause: the +5 V bridge and capacitor on the power driver board, or the connectors to the CPU. A fix that works: replace bridge BR2 and its capacitor, and clean the connectors.
- DMD. The high voltages of the DMD (around +62 and -100 V) are generated on the DMD controller or on the AV board. Dead or flickering display: start with the capacitors and resistors of the high voltage section. The DMD itself ages, and there are LED replacements.
- Fliptronics. Burnt flipper transistors or fuses on the Fliptronics board. Flippers without a power EOS switch use optos or small switches for the hold.
- Optical switches (optos). In the trough and on ramps. When it "loses" balls or thinks it has balls that aren't there, clean the optos and check their boards.
And the rest?
Gottlieb System 1 and 80, Data East, Sega and Stern Whitestar, Stern SAM and SPIKE: each with its own quirks. If you have one of these machines and you're stuck, send a message through the Contact page with the model and the symptom.