How to test if a pinball machine works ?

OK so you bought a pinball machine. Or you are looking at a pinball machine you consider buying. How do you know if everything is working ?

Note: this is just a quick overview guide, to help you if you have no clue at all about how a pinball machine works and what to look for when buying one. It is not 100% complete, and certain types of machines will be different. Do not hold me responsible if you bought a machine which has problems, even though you did what I describe in here and everything looked fine.

Also read the 'buying a used EM pinball' article on this Finnish website. I do not want to scare you, just inform you. Test the machine very well, and if it's too bad, it's better to search for another one for sale, as repairing a broken machine may cost a lot ! If the machine is in a too bad condition, it may not be possible to restore it, or its restoration may cost much more than the game ever will be worth.

For detailed repair and troubleshooting information, check
I only describe here how you can do some tests and how a pin should work. I deliberately do not write what test when i.e. a coil or switch does not work, and how difficult it is to repair the problem. Check the repair guide.
When using this page, if you notice the pinball machine you're looking to buy has a problem, it's up to you to decide. You now know the pinball machine isn't working 100% (even maybe isn't working at all !). It's up to you to decide if you will buy the pinball machine or not, if you let the owner fix the problem, if you negotiate over the price, .. 
Be warned though, that a simple problem can hide a difficult problem which you may never solve, or will cost a lot more to fix ! I.e. what do you do when a mechanical pinball machine does not start at all ? It may be something simple like a bad fuse, or even a bad plug. You probably can get the machine 'cheap' because it's not working, and the owner does not know how to fix it (or so he says). So you can't replace the fuse while he's looking, because then suddenly the machine will work again and the price will go up ? If you don't buy the machine, you may have missed the opportunity to get a cheap machine which indeed only needed a new fuse. However, if you do buy the machine, it may turn out the fuse blew because the transfo is bad and needs to be replaced, some other things have a short, and there are a zillion things wrong with it, so in the end you'll spend 6 months working on it and still it won't work, and finally sell it to someone else or use it as a parts machine. So when buying non-working machines, pay only what the parts itself are worth, or what you can afford to loose in case you can't repair it..

On electro-mechanical (EM) machines, the only way to know if everything works is to play it. Play the game, and pay attention to what happens. Do all bumpers and slingshots react when they get hit ? Does something happen when targets get hit ? Note targets which have a light in front of them, it is possible the light bulb is burnt out, but the target itself registers fine. To know the difference, does something happen when you hit the target ? Is there a sound, does the score add up ? And i.e. if you light the whole bank of targets (like when there are 5 targets in a row), does it reset ?
Take the glass of the playfield and use the ball to test each feature manually. This way you can simulate specific game actions you weren't able during gameplay (unless you're a top pinball player who's able to hit every feature in the game ?) Don't forget to start a 4-player game on electro-mechanical pinball machines.

Solid state machines made it a bit easier for you. They have built-in self-tests to diagnose problems, and they'll keep track of problems and warn you. Most of the time, they will say what is wrong (like which switches don't work) when you open the coin door or enter test menus. Williams/Bally WPC machines, even show a 'credit dot' to indicate there is a problem like this. (credit dot: the display will say 'CREDITS 0.' when there is a problem, and 'CREDITS 0' when all switches register fine. (when set on free play, you'll get 'FREE PLAY.')) Please note that a game without a credit dot or warning message does not guarantee the game has no problems at all ! There may be like a problem with the switch matrix or on one of the pcb's, and these problems usually are much more difficult to troubleshoot !
Also check the last time the game had restored its factory settings ! A credit dot will only appear after a certain number of games. If the game has just been reset, it will also not show a credit dot. Of course the self tests only work if the cpu boots correct. If not, it may have severe problems with its electronics..

Where to start

First step: switch the machine on. Only do this if you're quite sure the game actually works. If the game does not work at all, it may be a broken fuse (find out why the fuse has blown !). But the problem can be a lot worse, so let's hope you didn't start a fire or fry anything by switching the game on !
If a coil is energized all the time: turn the machine off ! Clay's tech pages have detailed information what you have to test BEFORE turning the game on, I suggest you do this if you come across a game you don't know of if it'll work or not..

OK next step. The game switches on and you don't see or smell smoke or so.. Do any lights come on ? On (very) old EM machines you may have to press the left flipper button to activate the lights.

On solid state machines, it's not that simple. They have a whole computer in them which has to boot. On old Bally/Stern games this is indicated by a led on the cpu board (top left in the backbox) which has to blink 7 (seven) times. Other brands have other indications, but the result should be the same. After initializing, the game should go in attract mode. This is indicated by flashing lights (look at the feature lights on the playfield), maybe some music, and a message on the displays like how many credits are on it. Most important: it should say game over and there are 0 credits on the game.

If the GI lights go on, but it does not go into attract mode, you have a (major) problem with the pcb's. (General Illumination lights just stay on all the time - in attract mode you'll see feature lights go on and off in patterns)
This can be caused by a lot of things. Some ICs can be bad (lets hope they're not obsolete), but most of the time, it is because of battery damage or corrosion. If you're new to pinball machines, stay away from these pins. Unless you know a lot of electronics, you probably won't be able to repair them yourself. You can try to find replacement boards, but as it's your first pin, better find a pin which works ! (unless you have to buy one cheap, and want to put considerable time in repairs before you'll be able to play it).
Don't be tricked in thinking something is an easy fix because the lights come on ! As long as the score displays do not show (alternating) numbers, there can be something wrong with the cpu.

On solid state games, there is a (rechargeable) battery on the cpu board, to keep settings and high scores. After a while these batteries start to leak, and the acid destroys the pcb. Check if the battery is still on there, has started to leak and how bad the damage is. If you're lucky it will be possible to repair it. If you're not so lucky, half of your pcb is gone..

Ok the game is in attract mode, now try to add a credit to it and start a game.

Now you should be able to play a game. Play it :-) Pay attention to gameplay. Does everything seem ok ? Do switches register when they're hit ? Do the game rules look normal to you, or does it already start multiball after you hit one target ? Btw are you able to finish a game, or does it continues returning pinballs ?

Accessing self-tests

This is done on every solid state machine using button(s) you have access to when the coin door is opened.

How many buttons there are, and which tests exist, depends a lot on the brand and model of the machine. Most (all ?) of the machines will be able to test lamps, displays, sounds, switches and solenoids.

  • On early Bally/Stern games, inside the coin door there is 1 button. Press this to advance through the tests. You will have to go through all the audits or switch the machine off to get out of this test mode.
  • 1986 - 1989 Williams games (system 11) have 3 buttons. The middle button toggles up or down. In attract mode, press the first button with the middle button up to access the audits and settings. Use the first button to go to the next audit/setting. Start button to change it. In attract mode, middle button down and first button will go through the tests. After you've reached the last setting, the game will go out of the test mode. A quick way to exit the settings menu: on the first audit, middle button in, first button - this will bring you to the last setting, put the middle button back high, and press the first (next) button and you're out of here :-) To access the test menu: from attract mode, press the first button while the middle button is in. Put the middle button back up and use the first button to advance through the different tests.
  • Data East machines (at least the Checkpoint I saw) have a similar system like Williams system 11.
  • Williams/Bally machines from 1990 to 1999 (WPC system) have 4 buttons. The middle 2 are used to change the sound volume. The left one is to put service credits on. The right one will bring you into the menus. There you can use the other buttons to navigate through them: first to enter a menu or make a change, 2nd and 3rd to go up and down, and 4th button to go back. Press the 'back' button to go out of the menus and into attract mode.

The lamp test

This test will light up all playfield lamps. Any light bulb not working, doesn't work :-) It may be burnt out (replace with a new one), have a bad socket, or a wire may be loose. To you the joy to find out.

Notice some machines make a difference in their tests between general illumination (GI) and feature lamps, and recent machines also have flashers.

  • GI means Global Illumination. These lamps are used to make the playfield less dark, and are all on (or off or dimmed) at the same time. You find these i.e. beneath slingshots and other plastics, or behind rubbers.
  • Feature lamps are controlled one by one. There are i.e. below the playfield beneath inserts and keep you up to date of what targets to shoot at, which have been hit, if a bonus is available, ...
  • Flashers are like feature lamps but they flash :-) You'll recognize them as these bulbs are larger then regular bulbs. They get a higher voltage, therefor they are only switched on for a small time (so they don't burn). They're used because they give a bright flash and thus are great to bring attention to a certain feature on the playfield.

If one GI lamp is out, and replacing it with a (known) good bulb doesn't help, the socket could be bad. This happens often on older machines, certainly if you see rust or corrosion on metal parts. This may indicate there will be corrosion on other parts of the machine as well, which may cause other problems (in the future). If a feature lamp is out, the problem can be the socket or a wire, but it may also be on the lamp driver board or somewhere in the wiring between the two..

Same for flashers.. btw notice that on recent Williams/Bally games there are also flashers in the backbox, don't only watch the playfield :-) Sometimes a flasher test will flash 2 lights at the same time. Sometimes this is marked on the display, it will give the name of the flasher with (2) behind it. Also note that recent (1994+) Williams/Bally games have a coin door interlock switch. This will cut off the high power when the coin door is open. You will not be able to test flashers or solenoids while the coin door is open (unless you press this button).

Switch test

switch test

In here you can test all switches. If a switch is closed, it will say so. All switches should work fine. With the playfield glass off, touch every switch by hand and it should register. Also take notice that on certain machines (WPC) switches which are closed when you turn the game on, are ignored because the game thinks they're bad. Open the switch and it should register as a hit.

Display test

This test will show all functionality of the displays. If they're (alpha)numeric displays, it'll count from 0 to 9, show all parts lit, and maybe single parts too. Check that all parts are working and bright. There shouldn't be flickering or have missing parts. On a DMD screen, it will light up everything, then go through each row and column. Again, everything should work fine. If a DMD screen has faded clouds in it (especially when it's completely lit), it should be replaced, because this can cause problems on the dmd driver board too ! If lines are missing, this usually can't be fixed (unless it's the old style of dmd and you see where a connector pin is broken). Some DMD's even have problems with burn-in: certain screens which are shown a lot on the dmd, are burnt in and can even be seen when the game is switched off !
Replacement displays or dmd's are expensive, make sure they work good enough so you won't have to replace them. Small or oversized replacement dmd's for Data East and Sega machines are even more expensive and may be impossible to find !

Solenoid test


This test will fire all solenoids, one by one. The display will shown an id number (maybe with description) so you know which one does not fire. All solenoids should fire. Check the manual, it will have a list of the solenoids and their positions, so you can identify them.
Even magnets will be shortly activated.

Note: if the game does not start or you cannot access the solenoid test, lift the playfield and operate each solenoid by hand. Just push the metal plunger which moves into the center of the coil. They should operate without applying much force. A coil which has a lot of friction, only goes half in or even doesn't move at all, can't be repaired and has to be replaced.
If you see the coil wrapper (the paper around the coil) is burnt, then do not do this test ! Switching the machine on will probably make this coil burn even more..

Sound tests

There is some sound, isn't there ? EM machines will have chimes or bells, solid state machines have computer generated sounds. These can change from basic tones (on 70ies pins) to full speech. If there's no sound at all, check the volume. Older pins have an adjusting pot in the cabinet (Stern: in the cabinet just below the speaker, old Ballys: on the sound board is a small pot; Williams sys11: against the left side of the cabinet). On WPC pins the volume can be adjusted using the 2 middle buttons when the coin door is open. Note that on WPC pins you cannot go below a default level, unless you enable this in the settings.
Williams System 6/7 (maybe older ones too ?) and Gottlieb sys80 games have a button on their sound card. Press it and it will run a selftest which cycles all sounds.

The self tests will have an option to play all sounds and music themes the machine knows. They'll play one by one (maybe you can repeat a tune).