So you've decided you want to run arcade games in the house, eh? Good on ya. There are a few caveats you should be aware of before you get started. First off, it can be very expensive, for a number of reasons. It can consume a lot of time and effort when you're getting started. It can really get messy and take a lot of space. That said, here's the skinny, divided into the same parts you saw in the primer.
You're going to need at least one PCB to play on your fancy new system. It's a good idea to know what games you want to play when you're building your system. Most modern games feature a unified connector called a JAMMA connector, named after the Japanese Amusement Machine Manufacturer's Association, which designed it. This connector, as mentioned in the Arcade Primer and explored in more detail here, features all the inputs and outputs necessary to run your arcade game. Every JAMMA game can be removed and replaced with another with only one connector - before this remarkably simple idea every game required its own connector with different specs than the one before it. If you set your Jamma Gear up with a JAMMA connector, you're going to find life is a lot easier for you. Naturally you're going to want classic games (basically anything released before 1989) so you'll need extra adaptors for your JAMMA connector. Keep that in mind, but don't worry about it yet.
Choosing the proper monitor can be one of the most daunting processes for the home arcade player. You have to do something or you won't be able to see your games.
Right off the bat I'll tell you straight up: you cannot use a VGA monitor. Period. Forget it. Put the idea out of your mind. There are several other display options available to you.
Once you've selected your monitor you'll need to select a suitable connector, unless you want to hardwire it to your Jamma Gear, which isn't recommended. Once you've got it, you'll be tempted to use it on other things, just because you can. The GameSX Custom Video Connector has been serving dozens of people worldwide for over five years! And it works, which is even more important. It handles all the necessary video signals, as well as audio. And it's cheap - about a dollar - and you can also get them by cutting up serial cables. Now we're hacking!
Find an old cheap computer monitor such as those used on the old Amiga or Atari ST computers. See here for a monitor selection guide, written specifically for consoles, but very applicable to arcade use. Just ignore the part about LM1881 chips and buying cables. Where you're going you'll have to make your own cables. These monitors can often be found for under $50 - check ebay and your local pawn shops. A favourite is the Amiga 1084 series. Pinouts for these can be found on GameSX.com. For connecting to an Atari ST monitor, check out this diagram.
Use an original arcade monitor, but since they're designed for industrial in-cabinet use this would require a custom box of some sort as well as an isolation transformer, and typically they never look as clear and bright as a consumer monitor without spending gobs of money. On the plus side they're large and very obviously capable of doing what you need. Expect to pay $100-150 for a crummy used 19-inch monitor, and up to $A.Lot for a larger newer display.
You could hack your existing TV set to accept the RGB signals delivered by your arcade games, but if you're willing to stick your arms into 20,000 volts of pure death we're not going to help you.
Convert the RGB signal from the arcade game to one compatible with your TV set. A tiny device called a Chroma Encoder can convert the RGB from your arcade games to TV-compatible Composite(Video), S-Video, and Component Video signals. The frequency that is outputted from some arcade games causes sync problems with certian brands of TV that can't handle non-standard sync rates. Some arcade games may need to have a LM1881 sync circut added in-line to the sync line of the converter board. Jrokhttp://www.jrok.com/project/sync_cleaner/sync_pics.html carries a sync cleaner chip also that is said to work on Golden Tee boards. Other jamma boards that need cleaning in their sync line are the Mortal Kombat, NBA Jam, and Killer Instinct series. Most board RGB converter boards will set you back around $75-125 and different versions can be found from crazyarcade.com, jrok.com, and neobitz.com. The neobitz board has been designed around the SNK hardware for the Neo-Geo systems and it may not be completely compatible with other non SNK boards. Neobitz.com has a list of non-SNK boards that work with the neobitz converter sucessfully.
As a last resort, and happily featuring the clearest prettiest results, you can use your VGA monitor - but it'll cost you. Arcade games almost without exception output RGB signals at a fifteen kilohertz (15kHz) horizontal frequency. This low resolution signal is the same as your TV set, but far below the minimum capabilities of a VGA monitor, which starts at 31kHz and only goes up from there. You can still use your VGA monitor, and you'll get a gloriously clear picture, but it'll cost you $200+ for a device called an Upscan Convertor. This is a device that captures and converts the RGB signal from your games and presents a VGA-compatible signal on the fly. The Japan-only X-RGB2 is widely believed to be the best solution for this - check ebay or your favourite videogame importer for availability. They're usually $225 as of this writing, but you can often find the XRGB-2 for $150+ on ebay.
Now you've got your game, and you've picked out a nice monitor from the monitor adoption agency, and you're wondering - how do you communicate with it all? Simple, my friend: Controllers. More specifically, custom-built controllers. It's important to remember that there's no connection standard in arcade games. If you want to tie all your wires together with your fingers and cover them with electical tape, no one's going to stop you. We don't recommend this approach - it gets messy, and is a sticky mess when it comes time to connect something new. Around here the NEO GEO Controller pinout serves all our needs. It has enough pins for even the most button-crazed games, it's cheap and readily available.
Have a look at our old, ugly and unclear Controller Primer for a brief lesson on how controllers work, and for the advanced student (and illustrated with better pics) the perpetually half-finished Controller Primer 2! Arcade PCBs all work the same way - one common line is connected to every switch on the control panel, and the 'return' line from each switch is connected to the properly labelled spot on the JAMMA Connector. You'll see in the next segment how the wiring actually works. Just remember there's a lot of wires, but each has a clear beginning and end point. It's not at all unlike 'connect the dots', and if a four year old can do it, so can you.
You can either convert existing controllers, which involves a bit of soldering and some thinking, you can build your own from arcade parts, or you can just pick up a NEO GEO controller and plug it in. The first option is a matter for another day. The second is pretty easy, but you'll have to make your own case for the parts. You could even, if you're so inclined, cut up an existing arcade control panel and use that.
Picking a power supply is possibly the easiest part of the job. You only need, for about 98% of the games you're going to play, five and twelve volts DC. An arcade-specific power supply is a very cheap and easy solution, but you may have trouble finding one. Typically they're $10-30 used - check ebay. You can also use a PC power supply, with only a few caveats - you can't use an ATX power supply without some serious effort, and some PC power supplies won't power up unless there's significant power draw. On the bright side you've probably got several kicking around in old computers you don't use. Grab one, plug it in, and see what happens.
Additional input by phreak97: If the problem with an ATX power supply is that it will not power up without being connected to an ATX compatable motherboard, then all you need to do to get it powered up, is bridge two pins of the large connector made to fit the motherboard. I do not know which pins off hand, but will update later once I have a power supply to mess with. Feel free to edit or delete this addition entirely if this is not the reason why one of these cannot be used.
Input from atom: I believe you want to connect pin 14 (PS ON) to pin 15 (ground). http://xtronics.com/reference/atx_pinout.htm
Lesson one: Do not, ever, under any circumstances, plug the audio output from your PCB directly into your stereo. Yes, it'll work, but not for long. The audio amp on the PCB is rigged to drive a speaker, and if you plug it into your stereo it'll get really, really hot. Try it and see - it'll be hot enough to burn you in a few minutes. If you don't have any speakers lying around (and nearly any speaker will do, be it from your car or stereo) you can buy a speaker to line-level adaptor at any car audio shop for about twenty bucks. Just tell 'em your deck doesn't have lineouts and your amp only has line-ins, they'll hook you up.