Introduction to Arcade Machines

Introduction
Sooner or later you'll want to learn more about your arcade game. Either you'll get curious about how it works, want to make fine tune and adjustment, or you maybe you're trying your hand at fixing your first game. This article will give you some very basic information about an arcade game. It's meant for the first timer/hobbyist who has never worked on a coin-operated game before but is interested in getting more familiar with their game.

The Basics: Three Parts of a Game
Whenever I'm explaining an arcade game to a person, I like to describe the basic components of a game. Most, but not all games¹, have just these three basic parts. They are:

• Power Supply: Powers the game and monitor. Usually located on the base of the game, and in some older games may be comprised of a few components.
• Monitor: Display for the game. Common sizes for classic arcade games are 19" monitors for upright games, and 13" for mini and cocktail games.
• PCB or Board: "Computer" component of the game. May be as simple as one board, or may contain a series of boards. Can be located in many places, but typically the PCB is on the side or back of the game. Varies greatly by game.

While these are the three basic components of a game, there is really a fourth component: the connectors. Many times this is overlooked, but it definitely worth mentioning. The Power Supply, Monitor, and PCB are all connected by this connector or Wiring Harness. For the purposes of this discussion, we'll count the joysticks and buttons as part of the connectors. If you think about it, this is pretty accurate: they connect us, the game player, to the game. A large part of troubleshooting arcade games is finding out which component is causing the problem and then either replacing or repairing it. One of the first things to check when looking at a game that isn't functioning properly is the connectors. Make sure everything is connected up properly before suspecting any of the three basic components.

Power Supply
The purpose of the power supply (PS) is pretty simple: it supplies voltage to the game and monitor so that they run properly. Typically, a power supply will provide +5V, -5V, and 12V to the game (Direct Current), as well as a ground line and +/- AC (Alternating Current). If your game requires those voltages, you're in pretty good shape as a switching power supply is a "modern" power supply that is easy to replace. Prior to the switching power supply, games came with custom power supplies. Sometimes they would supply odd voltages such as +25V, +30V, and even -12V. In some cases this means that a game can not be upgraded to a switching power supply. Instead the original linear power supply will need to be repaired.

Generally speaking, the +5V is what will be used to power the logic on the main PCB. The other voltages, if used, drive power to sound PCBs and amplifiers. 

You'll probably hear the term "linear power supply" as well as "switching power supply." These are basically the methods by which the AC from your house is converted into DC for your game. Linear power supplies are the older, propriatary power supplies that vary greatly from game to game. Switching power supplies, or "Peter Chou power supply" are newer and pretty standard. 

An example of a Linear Power Supply (Williams)		Switching Power Supply
Taito Linear Power Supply

Monitors
We could write many, many articles dedicated to monitors alone. But given that this is just an introduction to arcade games, we're only going to cover the basics here. 

There are a few different types of monitors:

• Raster Scan: The type of monitor that is much like your T.V. Raster scan monitors are used in games like Pac-Man, Donkey Kong, Street Fighter, and the like. They project images on the screen by using an electron beam to scan across the screen from left-to-right, top-to-bottom. Raster Scan monitors are generally available in normal and medium resolution. Nearly all games are normal resolution.
• Vector: This type of monitor is used in games like Tempest, Star Wars, Battlezone, and Asteroids. Instead of scanning down the entire screen, the electron beam is used to draw lines. These monitors operate more like an oscilloscope than a T.V. 

The most common work that a hobbyist will do to a monitor is a cap-kit. This is simply replacing all of the electrolytic capacitors that are used in a monitor. Over time, capacitors wear out as the material used in the cap evaporates. Do not attempt to do a cap-kit unless you are thoroughly familiar with discharing a monitor (not covered in this article). A cap-kit usually improves the sharpness and contrast of a monitor, but usually² does not fix a broken monitor. 

The monitor is probably the most unreliable of the components of an arcade game. If your game is "playing blind" (that is, you can hear everything, but you can't see anything on the screen), then you know that your power supply and PCB are working. You have something wrong with the monitor or connection to the monitor. Monitor trouble-shooting is very specific to the monitor that you are working on. However, with the appropriate monitor documention and a multimeter, most monitors can be repaired. 

Tapper, a Raster game

Asteroids, a Vector game

With the exception of vector games, arcade games were not released with a specific monitor. So, if you find that your monitor needs to be replaced, you don't have to search for the exact monitor for your replacement. In many cases you can replace it with a generic monitor, new or used. 

PCBs
The "brains" of the game is the PCB. This part of the game can be as simple as one board, or several boards wired together. For the beginner hobbyist, there isn't a lot that you can do once you've identified the problem as being PCB related. That being said, there are a couple of cases where the board can be fixed rather easily. If you think you have a problem with the board, first try reconnecting the board where the board plugs into the wiring harness. What you're really doing is making sure that the connection to the board is good. If that doesn't fix the problem, then try pressing down gently on chips that are in sockets. Sometimes the connection between the chips³and the board is faulty. In fact our experience has been that it's just as likely (if not more likely) that the sockets have gone bad rather than the problem being the ROMs themselves.

An example of a PCB (Donkey Kong PCB, two board version)

An example of a JAMMA compliant PCB (Silk Worm)

One of the most common PCB related questions is game compatibility. Around 1986-87 a wiring interface standard known as JAMMA (Japanese Amusement Machine Manufacturers Association) was established. Since then, most, but not all games, have adhered to the JAMMA pinout standard. If you have a cabinet with JAMMA wiring, it is usually easy for you to rule in or rule out a board being defective. For more information about board compatability, read Anthony's article PCB Swapping 101. 

Conclusion
This article was meant as a primer for understanding arcade games. In the near future I'll write an article that ties together this information with some basic troubleshooting.