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Conversion FAQ


COPYRIGHT 1994

REVISION NUMBER: 1.1
REVISION DATE: 02 November 1994

REVISION HISTORY: 1.1
(02/11/94 - Clarified technical details in {6.4}, Added a few words on manuals in {7.3} and analog controllers in {8.1.3})
REVISION HISTORY: 1.0
(01/11/94 - First public release; FTP only)

CREATED BY:
Doug Jefferys, Steve Ozdemir

WWW version by Frederic Vecoven (veco@montefiore.ulg.ac.be)

THANX TO:
Wayne Aiken, Graham Bisset, Duncan Brown, David Hanes, Tony Jones, John Keay, Patti Ozdemir, Alex Ozdemir, Hedley Rainnie, Rick Schieve, Gregg Woodcock.


STANDARD DISCLAIMER

The authors hereby grant permission to reproduce and distribute this document for personal use, subject to the condition that the document (along with any copyright and disclaimer notices) is not modified in any way. The opinions expressed within this document are those of the authors only and not necessarily those of the authors' employer(s). This document is provided for informational purposes only. Although the authors have made every effort to provide accurate information, they cannot guarantee the accuracy or usefulness of any of the information contained herein due to the complexity of the issues involved. The authors take no responsibility for anything arising as a result of anyone using the information provided in this document, and the reader hereby absolves the authors of any and all liability arising from any activities resulting from the use of any information contained herein.


Introduction

Arcade video games are surprisingly simple beasts. They use power, control panel inputs, and coins (lots of coins!) to display pictures on a monitor. When you play a video game, you're interacting with a dedicated computer built to play the game in question. Conversion is merely the process of changing the computer inside the box to play something else.

Sometimes, all you have to do is change the software. Stored on EPROMs, software changes can be as simple as swapping a single chip. A chip swap like this, for instance, will upgrade a TMNT (Teenage Mutant Ninja Turtles) board to play Turtles In Time. Often, however, things are more complex, and may require different power supplies, new control panels, wiring work, and more. Although monitors are normally never swapped from game to game, they may also have to be rotated through 90 degrees, or have their input signals manipulated. The "right" approach to any given conversion varies depending on the games in question and the resources you have available.

Resources come in many forms, but the most important resources are money, time, parts, and knowledge. Money is a useful resource, and is most commonly used to acquire parts. Time is spent, both in finding parts and in bending them to fit the task at hand. Parts are probably the most fundamental resource, as they're the building blocks of your conversion. Some parts are rare and require long, expensive searches. Other parts are cheap and commonly available, but require a few hours of work before they can be made into the games you want. Tony Jones is maintaining a list of parts suppliers; see reference {9.3.1} for details.

Knowledge is the last piece; it enables you to combine the three other resources into the games you want. Getting a hold of this FAQ is a good first step towards acquiring that knowledge; trying some conversions will be the next step. Old video game manuals are extremely useful, but are increasingly difficult to find. And of course, there's always r.g.v.a.c. if all else fails :-)

The types of resources available vary from place to place. If you've got a warehouse next door where you can buy any game for $10, you'll be doing conversions that minimize time and assume that you have a complete copy of all the parts you'll need. If the nearest warehouse were 500 miles away, you'll be either spending a small fortune to have a few precious parts shipped to you, or you'll be building a lot of goodies from scratch.

Finding what you need, even if you're close to a warehouse, can be difficult. Some parts are valuable, even though the games in which they were used were total failures in the arcade, because they're Just Plain Rare; while demand for such parts is limited, supply is even tighter. While bulk buys of boards are often a good way of getting parts, nothing is guaranteed.

What we're trying to emphasize here is that no one approach is intrinsically better than another. Often, an approach which makes sense for your situation won't make sense when applied to someone else's. There will even be times when an approach that made sense to you at one time won't make sense to you today.

We've neglected to mention one other resource -- space. While space has nothing to do with the feasibility of a given conversion, it's probably the most important resource a video game collector has, as it limits the number of cabinets he/she can install. As such, folks with lots of space may be able to build up substantial collections without conversions. Those of us who live in the real world, however, aren't usually so lucky -- space is valuable, and saving space is what conversions are all about.

Hence this FAQ. Still, don't expect it to give you the "universal" approach that allows you to play any game in any cabinet, because, as demonstrated in our earlier discussion about resources, no such approach exists.

What you *can* expect from this FAQ, however, is a set of descriptions about many different approaches to the task of conversion and some attempts to explain what conditions suggest a given approach. Again, these "conditions" are only guidelines. In the real world (especially when you do your first conversion), things won't be as easy as they seem after reading this FAQ, but at least you'll have been exposed to the various approaches out there. With luck, you'll at least be able to think about which approach might be right for you and your task at hand.


Anatomy of a Video Game

Since games are what it's all about, let's take a typical video game and slice it up into its principal components:

  1. Monitor
    • That TV-like thing that displays the pretty pictures. Monitors come in two flavors: Vector and raster.
    • Vector monitors display straight lines using the same principles used by oscilloscopes; an electron beam is deflected from one point to another, leaving a line between the two points. Consequently, these are also known as "X-Y" monitors. These are becoming increasingly rare, as the last vector game was made in 1985, almost a decade before this FAQ was written.
    • Raster monitors are more like televisions, in that the electron beam scans over horizontal rows of pixels, illuminating varying levels of red, green, and blue (RGB) phosphors. Raster monitors are the only type of monitor still in production for video games.
    • Vector monitors are *not* interchangeable with raster monitors. If you want to run Tempest in your Arkanoid cabinet without buying a new monitor, forget it.
    • Laserdisc games use raster monitors. These games use normal RGB montiors, but have additional circuitry to convert the NTSC output of the laserdisc to the RGB input that the monitor expects.
  2. Controls
    • All controls perform the same function: conveying your actions to the game board.
    • There are many kinds of controls. Basic buttons, basic joysticks (digital, with switches, or analog, with potentiometers), encoder wheels (those funky spinning knobs, also common in driving games), trakballs, and more exotic critters such as Hall Effect joysticks, optical joysticks, funky light-detecting guns, force-feedback mechanisms (like in Hard Drivin') and lots of other things which are beyond the scope of this FAQ.
    • Coin doors are glorified buttons. There's some extra mechanical magic that allows them to differentiate between quarters and other coins, but you can treat them as pushbutton switches for the purposes of this discussion.
    • Games with *really* odd controls, like Discs of Tron's encoder wheel (which can be pushed in and out as well as rotated), or the eight-position rotating knobs from Ikari Warriors, tend to be very difficult to convert. It's often best to make sure that such specialized hardware comes with the boards.
    • Still, people *have* managed to do workarounds for weird controller schemes. The optical and hall effect sticks, (used in Sinistar and I, Robot respectively) have reportedly been obsoleted via such means. Reference {9.2.1} describes the hack for Sinistar.
  3. Speakers
    • Okay, so there's not much high-tech about speakers. You stick some signal into one end, and sound comes out the other end. The reason we mention them here is because the signal that comes off the board comes in two flavors: amplified and unamplified.
    • Amplified signals are the easiest to deal with. Stick 'em onto your speakers and enjoy the sound.
    • Unamplified output is a little tricker; it needs to be amplified before you'll hear anything. On an original game with unamplified sound (including most older Atari games, Universal's "Mr. Do" series of games, and many older Midway games), there was an audio amplification board somewhere in the cabinet that served this purpose. Odds are that you didn't get it when you got the game board, though, so you might have to build your own instead.
    • If you're going to try and run both types of audio in the same cabinet, you'll have to pay special attention to this issue, usually by putting an amplifier between the board and the speakers, activated when required by an external switch.
    • You can make a quick-n-dirty audio amplifier with an LM380 op-amp as follows: Put unamplified audio on one side of a 10K volume pot and the other side of the pot to GND. The center tap of the pot is connected to pin 2 (the input) of the LM380. Pins 7 and 3 of the LM380 go to GND. Connect pin 14 of the LM380 to +12V DC. (Don't forget an 0.1 uF decoupling capacitor between +12V DC and GND). Pin 8 of the LM380 (the output) gets a 2.7 ohm resistor in series with an 0.1uf cap to GND to prevent the chip from oscillating. Finally, stick the positive end of a 250 uF electrolytic capacitor to pin 8; the negative end of this capacitor goes to one of the speaker leads. The other speaker lead goes to GND. Power it up, and away you go!
  4. Power supplies
    • Turns ugly 120V AC power into nice, clean DC voltages usable by the board's electronic components.
    • Linear power supplies have large, heavy transformers and produce voltages which must still be regulated by other circuitry, usually located on separate pieces of hardware within the cabinet, and in rare instances, on the game board itself.
    • Switching power supplies are much lighter, cheaper, and easier to work with.
    • If you've got a vector game which needs a bunch of exotic voltages, you may not be able to find a switching power supply which suits your needs. You'll have to hunt around until you find the original (linear) power supply that was used with the game.
    • Some boards require only +5V and GND. Most require +5V, +12V, and GND. Older Williams machines may also require -12V. Other games require bizarre AC voltages, or high voltages like +25V. The stranger the power requirements, the more work you'll have to do to get things running without resorting to the game's original power supply. Vector games tend to have the strangest power requirements owing to the nature of their output circuitry; the vast majority of raster games can be run on +-5V and +-12V. You may not get all the features your game had (like electronically-erasable EPROMs to save the high score table), but you should be able to at least play the game.
    • "Normal" switching supplies are easily replaced; a standard IBM PC power supply will give you everything you need to power up most boards. Many collectors will replace an old linear power supply with an arrangement like this (or with a regular game switching power supply for $30 or so) in order to save themselves trouble down the road.
    • Linear supplies are much more difficult and are usually specific to one manufacturer and/or time period. Even then, it's easy to make mistakes -- the transformer associated with the linear power supply used by Atari's B/W vector games and some of their raster games is *NOT* compatible with the one used by their color vector games.
  5. Boards
    • The brains of the operation. Contains all the circuitry required to eat the power and your control inputs, and spew the results out to the monitor and speakers.
  6. Wiring harness
    • The glue of the operation. A set of wires that connects the preceding four chunks of hardware together. Not as simple as you might think, because gluing all these parts together requires connectors, and the required connectors are almost *always* difficult to find locally, and can also be expensive. If you don't have any luck locally, you'll have to find a good mail-order place and do your shopping the hard way :-)
    • If you *do* manage to find a source for connectors, on the other hand, building a wiring harness by hand, while time- consuming, is a fairly simple operation. This is a Good Thing, because original harnesses for older games are practically nonexistent.
  7. Cabinet
    • The wooden housing into which all of the above get crammed to create a video game. Heavy, bulky, and generally a pain to lug around. On the other hand, often beautifully decorated, and definitely something to take good care of if you've got one in good shape...
    • You *can* make a cabinet yourself, but it takes a lot of work. And a lot of time. And a lot of wood. And a lot of skill. And a lot of money. Minor restoration is tough enough; building a cabinet from scratch isn't recommended unless you have truly nightmarish space problems that would prohibit you from bringing in any form of "real" cabinet.
  8. Miscellaneous/specialized/custom/unique hardware
    • Spherical mirrors that reflect the image up (e.g. Time Traveler)
    • Video conversion equipment: Overseas folks may not have NTSC-compatible hardware. If a game puts out NTSC, it may have to be converted further to another format such as PAL or SECAM in order to be of use. Information on PAL, SECAM, and other video formats is beyond the scope of this FAQ; interested readers are encouraged to consult the newsgroup "rec.video" for further information.
    • Laserdisc equipment: Not only the discs themselves but the players and the NTSC->RGB conversion boards which convert the laserdisc player's output (a NTSC signal, such as that used by a television set) to the RGB signal (used by the monitor).
    • A recent development in arcades is the use of projection TVs. These are also raster displays, but they use an NTSC signal, as opposed to the more common RGB signal set. There's a small board inside such games which converts RGB to NTSC.
    • Keyboards (Thayer's Quest, Space War)
    • Joysticks with spinning knobs on the ends (Ikari Warriors)

Conversion Classes / Hardware Families

We just finished telling you that you couldn't put all the video games in the world into one cabinet. And we meant it... well, sort of. If you plan your purchases carefully, you can still get a lot of games in a fairly small number of cabinets.

The key is to divide the games into families of similar age, manufacturer, and display hardware. Consider the following sample "conversion classes"; the list below is by no means exhaustive, but should give you an idea of how various games are grouped.

The "conversion classes" are grouped into two sections, vector and raster. These refer to the type of display used by the games in question. Each vector class is further grouped around the display technologies used by the respective manufacturers. Although each manufacturer and display technology is different, the hardware driving any particular manufacturer's technology is similar, leading to a set of fairly easy conversions.

For example, Cinematronics used essentially the same hardware (with very minor modifications) for all of its B/W vector games from 1977 (Space Wars) until 1981 (Solar Quest). All in all, they produced over 10 games using the same bit-sliced architecture, even though microprocessor-based vector games had been around since 1979 (when Atari introduced Lunar Lander).

Even when the hardware changes, the display technologies remain the same. Despite many changes in design of monitor and hardware, all of Atari's B/W vector monitors remained interchangeable, and so were all of their color vector monitors. While two of their games (Tempest and Quantum) mounted the monitors vertically, the monitors were identical with those used in their previous games.

For the more common raster arcade games, each class is only centered around similar hardware, as the display technology has remained static over time. Physical orientation (horizontal/vertical) of the monitor, sync type (composite/separate), and sync/color polarity (positive/negative) may vary, but these can all be compensated for with external circuitry.

Most hardware platforms were similar only for a few years at the longest, so you'll notice that the raster games listed in a particular year also were made about the same time. After a few years (or in some cases, a few months), larger memory chips, faster processors and other hardware could reduce costs and allow bigger, fancier and more complex games to be developed for the same price, and the manufacturer developed new hardware to match the new technology. The "new/old Williams" series of games are prime examples of technological evolution in action.

In modern times, everything has been standardized so that conversion classes are based on pinouts, not game hardware. The JAMMA standard and the earlier Konami standard are examples of this; these conversion classes exist because manufacturers agreed to use the same pinouts, regardless of the (often radical) changes in hardware design from game to game.

The advantage of breaking games down into conversion classes is that it gives you an easy way of evaluating whether or not a given board is immediately useful to you, or whether you'll have to do substantial work to get things running. Someone with an Atari color vector game at home can go into any operator's warehouse and *know* that they should be able to use (or at least test), fairly easily, any Atari color vector boards they may happen to find, but that the (Sega) Space Fury set in the nearby pile may require a lot of work. If they only have enough money or time to pick up one pile of boards, the Atari color vector pile is definitely the one to go for. No need to waste the operator's time asking "gee, can I plug this into my Gravitar machine at home?", just an internal mental note of "yup, I can use this easily", or "nope, I haven't a *clue* what to do with this one".

It also gives you the advantage of knowing what's easy to trade. Even if you don't have the equipment required to run (or even *test*) the Atari vector games in the hypothetical pile above, you can know that someone out there will. If you've got the cash, and the pile is there, just grab it and trade with other collectors to get boards you *can* use.

Vector game conversion classes:

Atari Color Vector
Gravitar, Space Duel, Black Widow, and possibly Quantum
Major Havoc, Tempest
Star Wars, Empire Strikes Back
Atari B/W Vector
Asteroids, Asteroids Deluxe, Lunar Lander
Battlezone, Red Baron
Cinematronics BW Vector
Rip Off, Star Castle, Armor Attack, Solar Quest
Sega Color Vector
Space Fury, Eliminator, Star Trek, Tac Scan, Zektor

Raster game conversion classes:

Atari
Centipede, Millipede, Xevious, Dig Dug, etc...
Gottlieb
Mad Planets, Reactor, Q*bert
Midway
Galaga, Bosconians, Mappy
Midway
Tron, Discs of Tron
Nintendo
Mario Brothers, Donkey Kong, DK Jr., DK III, Popeye, etc...
Pacman
Pacman, Ms. Pacman, Pacman Jr., Pacland, Galaxian, but (hey, there's always one exception :-) *not* Super Pacman.
old Williams
Robotron, Joust, Stargate, Defender, Sinistar, Bubbles
new Williams
Blaster, Joust II, Mystic Marathon, Inferno
Laserdisc games
Dragon's Lair, Space Ace, Thayer's Quest, Super Don Quixote
Konami standard wiring harness
Time Pilot, Super Cobra, Scramble, Frogger, Gyruss, and many more.
JAMMA standard wiring harness
Many games now use the JAMMA pinout standard. Getting a JAMMA cabinet will make the rest of your collecting life much easier. Since JAMMA is newer, more common, and (most importantly) has *more pins* than the Konami connector, it's generally easier to work with. Besides, you can always build an adaptor to play Konami games in a JAMMA cabinet. (Adaptor, you say? Playing games in other cabinets? Hey, sounds like a conversion! We'll be seeing more of this later...)

Using conversion classes to have it ALL:

Getting back to the issue of conversion and your arcade video game collection, we'll use the above conversion classes and a sample game collection to try and "cover" all your favorite games.

Suppose you'd like to have the following 12 popular games:
- Tempest, Battlezone, Asteroids, Star Wars, Joust, Space Duel, Stargate, Gravitar, Defender, Robotron, Star Castle, Sinistar

Robotron is in the "old Williams" conversion class; it'll make a nice home for Joust, Stargate, and Defender. Stargate will require a new control panel, Sinistar will require a fair bit of work, but might also be done if you can find the parts, and Defender has a unique board set, but you could probably work something out without much difficulty, as it will plug directly into a Stargate harness.

Space Duel is in the Atari color vector conversion class, which covers Gravitar, Tempest, Major Havoc, and possibly Star Wars (although Star Wars, Major Havoc, and Tempest will need the proper controls...)

Rip Off is in the Cinematronics B/W conversion class, which gives you Star Castle.

Finally, Asteroids Deluxe provides a home for Asteroids and Battlezone (although again, you'll have to worry about the Battlezone control panel).

Not bad. 3 manufacturers, 4 cabinets, 14 games. We'll see later that the Asteroids<->Asteroid Deluxe conversion, the Rip Off<->Star Castle conversion, the Joust<->Robotron conversion and the Space Duel<->Gravitar are extremely easy due to the similarity of controls and hardware. At any rate, we've covered a large proportion of the most popular classics, and we did it by starting with four commonly-available (and thus less expensive) games, namely Rip Off, Space Duel, Robotron and the extra Asteroids Deluxe.

Indeed, you can get more games out of these cabinets, including Bubbles, Black Widow, Major Havoc, Red Baron, Armor Attack, and Solar Quest, so you really have 20 games in your four cabinets. Not bad for a day's work. Even if you don't particularly care for all of these games now (and indeed, you may not have even *heard* of them!), you might feel like adding them to your collection in the future, just to try them out. Conversion gives you the flexibility to do this without having to carry home another six cabinets (on top of the 14 you'd have already purchased if you were trying to do this without conversions) for these relatively obscure games, "just to see if you like 'em". You can also buy the boards or other hardware for each new game separately for far less than the cost of a full-sized cabinet.

For bonus points, use some of the space you've saved so far to buy two JAMMA cabinets, one with a vertically-oriented monitor and one with a horizontally-oriented monitor. You now have the potential of doing conversions for your older raster games to JAMMA (of course, if you enjoy newer games, they may already *be* JAMMA!), and being able to add literally hundreds of games to your collection without taking up any more space whatsoever. Every bulk buy you do should net you several games you can convert to JAMMA, which can drastically expand the size of your arcade at minimal (financial and space-wise) cost.

If you can't appreciate reducing the space (and cost!) that your ideal arcade takes up by a factor of three, then you're either rich, single, live in a *BIG* house, or all three. Put another way, just discuss the matter of putting a dozen full-size arcade games in your parents' garage or significant other's apartment and you'll soon realize that conversions save more than just space!


Conversion Theory

As we mentioned before, several approaches exist to doing a conversion. Each approach has advantages and disadvantages, including ease of construction, cost of parts, and space occupied. We'll discuss four of the most popular approaches here:

Plug-n-chug: Swap motherboards. No homebrewed hardware, soldering time, or brains required, and thus much favored by operators :-). The JAMMA standard is based on this philosophy.

Control panels: Sometimes you'll have to hack on the control panel, or even make an outright swap of old one for a new one. Not really a conversion per se, but we include it here because it's a very common technique that is often required when doing conversions of any type.

Adaptor-hackery: Swap motherboards, but stick an adaptor between the new board and the old harness. If edge connectors are easily available in your area, this approach can be both cheap and relatively quick. This approach is very commonly seen in collector circles, but due to the time required to creating the adaptor in the first place, its use among operators was limited, even in the days before JAMMA.

Banking, or EPROM-hackery: EPROMs, Rube Goldberg-like adaptors sitting on motherboards, and the sweet scent of solder. Run two (or more) games off the same motherboard with the flick of a switch. Time-consuming to build, and requires a bit of electronics experience. Never used by operators for these reasons (plus the fact that operators don't need to switch games frequently -- it's easier for them to just swap boards and maybe insert an adaptor every few weeks when earnings drop...), but very useful for collectors who have a hard time finding video game parts.

All-in-one: Putting the guts of more than one game in one cabinet. Like other conversions, it saves space and time, but requires a lot of manual labor. This approach is never used by operators (who merely wheel in a new board or machine when it's time to switch), but can be useful for a collector with a roomy cabinet and two (or more) complete wiring harnesses on hand. This is a relatively rare situation; if you have to construct the wiring harness yourself, you're probably better off using one of the other methods.

"Plug-n-chug", or "Board-swapping":

This is the simplest type of conversion. You simply power off the machine, disconnect the board set, and insert a new board set. Powering up the machine completes the conversion; you've got a brand-new game.

Sadly, not every conversion is going to be this easy. You can't do this at all unless the pinouts for the boards are identical, which is often not the case, even for fairly recent games. And it's almost *never* the case for older games.

The JAMMA (Japanese Arcade Machine Manufacturer's Association) pinout standard (a 56-pin connector) was developed in an attempt to rectify this situation; by providing a standard pinout, any JAMMA board can be plugged into a cabinet with a JAMMA wiring harness.

Earlier attempts at standardization included the Konami wiring standard (early 1980s, using a 36-pin connector), the Universal wiring standard (the entire Mr. Do! series of games, Ladybug, and a few others used a 56-pin connector, but one that is *NOT* compatible with JAMMA), and the Sega wiring standard (mid-1980s, also using a 56-pin connector, and *ALSO* incompatible with JAMMA). Some early Capcom games also fit this pattern - 56 pins, but not JAMMA.

The point we're making here is that while most recent games are built to the JAMMA standard, other standards *do* exist, and you should be aware of them. Under no circumstances should you assume that a board with a 56-pin connector is automatically JAMMA, unless you've looked very closely at it first.

Some manufacturers make it easy for you - printing the word "JAMMA" directly onto the PCB. Others don't. Your best bet is to get the pinouts for the various standards (Reference {9.3.2} (the stormaster.com FTP site) is the best place to find them online), and compare them with your board. If you get a match with any of them, you'll either be able to play it in your harness, or construct an adaptor to fix the problem. Adaptors will be discussed in the next section.

Hacking or swapping control panels:

So you've just compared two sets of pinouts and seen that they're basically the same. You plug the new board in, power things up, and everything works fine until you try and start a game. You then remember that the controls are different.

Bummer, eh?

Well, not really. 90% of the work has already been done; the game is up and running, so the rest is just a matter of wiring.

As an example, we'll take Gravitar and Space Duel. These boards have identical pinouts for power, sound, and video, so you can just "plug-n-chug" to power things up. As the control panel portions of the games' pinouts differ, you've still got a little more work to do before you've finished the conversion.

(In case you're wondering why the panels were made incompatible, Atari didn't want to make it too easy for operators to have their cabinets playing different games -- this was before JAMMA, back in the Golde^H^H^H^H^HDark Ages when each game came in its own cabinet, with its own artwork, marquee, and control panel.)

What this means is that if you're trying to put a Gravitar board in a Space Duel cabinet, you'll need to rewire it using a switch with six poles -- to swap the six signals going to the panel, depending on which game you're playing. The end result should look something like this:

PCB    Space Duel controls      Corresponding button on Space
pin    wiring harness pin       Duel panel for SD or Gravitar
                          _________P2 Rot R (for playing SD)
19-E_______Pin 3_________/
                         \_________P1 Rot L (for playing Grav)

                          _________P2 Thrust (for playing SD)
20-M_______Pin 4_________/
                         \_________Select Sw (for playing Grav)

                          _________P2 Fire (for playing SD)
19-4_______Pin 5_________/
                         \_________P1 Fire (for playing Grav)

                          _________Select Sw (for playing SD)
20-11______Pin 7_________/
                         \_________Start Sw (for playing Grav)

                          _________P1 Fire (for playing SD)
19-3_______Pin 11________/
                         \_________P1 Shields (for playing Grav)

                          _________Start SW (for playing SD)
19-6_______Pin 14________/
                         \_________P1 Thrust (for playing Grav)

The rest of the control panel inputs don't matter since they are either the same (i.e. both games use the same PCB pin for the button/game function) or left unused by Gravitar.

The other option, if you don't have a six-pole switch handy, but you *do* have a Gravitar control panel handy (remember we talked about "resources" earlier?) is to simply swap panels. Rig up an adaptor to go between the Gravitar control panel and the rest of the Space Duel wiring harness. As you're only interested in the control panel inputs, this can often be a convenient "shortcut" around the adaptor hackery route which we'll be discussing next.

This was all about adding a Gravitar board to a Space Duel cabinet. Going the other way with a simple control panel swap is much more difficult, owing to the larger number of inputs required by Space Duel. These difficulties will be discussed in more detail in the next section.

"Adaptor-hackery":

For all practical purposes, hacking or swapping control panels is really just a sidetrack from the types of conversions available; it's something done to facilitate a conversion, rather than being a conversion in and of itself. At the end of our discussion on control panel hackery, we mentioned that one could construct an adaptor that would go between the new control panel and the old wiring harness. Since you have to swap both the board *and* the control panel, and since these two parts are normally located fairly far away from each other in most cabinets, why not move the adaptor to the other end of the wiring harness? There are times when it's much easier to simply place the adaptor with the new board itself.

Such adaptors are the next-simplest form of conversion. They're what you usually build when your new board doesn't match the wiring harness of the game you're trying to play it in. They take a little time and effort to build, but are almost always worth it. Experienced collectors will often accumulate large "libraries" of adaptors to use with their games.

To build an adaptor, you'll need accurate pinouts for both your wiring harness and for the board set(s) you're trying to plug into it. Of course, if the pinouts match, you've got a "plug-n-chug" situation, and no adaptor is required.

If not, however, you might consider modifying the board to suit the harness. This is generally a *bad* idea; you'd like to keep the board as intact as possible, if for no other reason than you'd like to be able to trade it with a friend someday, or send it off somewhere to have it fixed. Moreover, cutting leads and soldering wires directly to a board may also damage it, create unreliable solder connections, and may also make debugging your work more difficult. On the other hand, adaptors require parts, and if you're *really* desperate for parts, you may have no choice but to modify the board directly, even if you may regret it later.

Rather than modify the board directly, most people build an adaptor to stick on the end of the board. This is a little device composed of some connectors and wire, and it maps the board's pinout to that of the wiring harness.

To construct an adaptor, look at your wiring harness, the old board that lived there, and the new board you wish to plug into it. What you want to do is create something that will make your new board "look like" the old board (from the perspective of the old wiring harness), and your old wiring harness "look like" the new board's harness (from the perspective of the new board).

For instance, if your old board (and thus, old wiring harness) used the JAMMA standard, you'd want your adaptor to have a 56-pin male edge connector on one side. The combination of "new_board+adaptor" should look like any other JAMMA board. If your new board were, say, a Dig Dug board with a 44-pin male connector, you'd want the adaptor to have a 44-pin female edge connector on the other side. The combination of "old_harness+adaptor" should match Dig Dug's pinout.

Between the two sides of the adaptor, you'd have a set of wires, carrying the JAMMA harness's +5V to the proper pins of the Dig Dug female edge connector, and the Dig Dug video output pins to the proper pins of the JAMMA harness.

The end result would look something like this:

        --------< <-----------> >--------~~~~~\/~~~~~~~~~~------<
TO      --------< <-----------> >--------~~~~~'\/~~~~~~~~~------< DIG
JAMMA   --------< <-----------> >--------~~~~~~'\/~~~~~~~~------< DUG 
WIRING  --------< <-----------> >--------~~~~~~~'`~~~~~~~~------< PCB
HARNESS --------< <-----------> >--------       /~~~~~~~~~------<
        --------< <-----------> >--------~~~~~~'    
        56-pin      male-male   56-pin     Wires that map  44-pin
        female      PCB with    female     JAMMA pinouts   female
        edge        straight    edge       to 44-pin Dig   edge
        connector   traces      connector  Dug pinout.     connector

In this simpler case (where the pinouts from the new game are a subset of the older game's pinouts), you can just ignore the "extra" pins on the wiring harness. Dig Dug only had one fire button, so you don't need to hook up anything for the JAMMA standard's other two buttons.

On the other hand, if your wiring harness is for the board with the smaller number of pinouts, then you may have to enhance the wiring harness to take into account the "extra" leads for the new game. The JAMMA standard has enough pins for most games on the market, both old and new, and thereby avoids this problem; this is another reason for its popularity. Even if you can swap control panels easily, putting an SFII board set into a Dig Dug cabinet is going to require some modification of the Dig Dug wiring harness to carry the extra button signals to the control panel.

The point of all this is that no adaptor can make up for the fact that your new game may want three more buttons than your old cabinet supported. At least, not unless you feel like drilling holes in your nice, clean control panel and making extensive wiring harness modifications. As such, adaptor- hacking approach is best used for cabinets with *lots* of buttons or sticks. Games like Rip Off, Space Duel, and SFII have tons of buttons to play with; it isn't a coincidence that we suggested two of these three cabinets earlier in this FAQ. As of this writing (October 1994), the price of SFII games has dropped dramatically over the past six months, so you may want' to consider an SFII cabinet for your horizontal JAMMA machine.

At any rate, if you have the choice, work from a JAMMA cabinet. If you can't find a JAMMA cabinet in the right price range, you could also consider getting a non-JAMMA cabinet, removing the original wiring harness, and putting a JAMMA harness.

Similarly, if you're going after Atari vector games, go for a Space Duel cabinet if you can find one. It's got *LOTS* of pins on its wiring harness, and should be able to handle any other Atari vector game you decide to throw at it.

One final note: the adaptor-construction approach requires parts that you're not likely to find at your local Radio Shack (edge connectors, male-male PCB pieces, etc...). Unless you live near a really good electronics store, or an operator's warehouse, you'll probably have to mail-order some stuff in. On the other hand, at least the parts required aren't unique to any particular game, so you can pick up a big pile of parts at once and never have to worry again.

See section {8.5} for some alternative methods of adaptor construction.

See reference {9.1.1} for an example of this kind of hackery as applied to Asteroids and Asteroids Deluxe.

See reference {9.1.2}, (Space Duel -> Gravitar), for more details on how to modify a Gravitar board to put it into a Space Duel wiring harness and an example of this technique.

Finally, adaptors don't have to deal with edge connectors only. See reference {9.1.3} (Joust -> JAMMA) for a series of adaptors that will allow you to convert the complicated board set for Joust (and by extension, other Williams games) to JAMMA. This hack also involves the inversion of the game's sync polarity, which is explained in more detail in section {8.6.3} of this document.

"Banking", or "EPROM-hackery":

This approach requires a complete understanding of the hardware architecture of the similar games AND how the hardware addressing works so you can use a larger EPROM to hold multiple games.

Because this type of conversion requires detailed technical knowledge, it probably isn't appropriate for a beginner who has no help. On the other hand, a beginner with the schematics of the games in question and a little electronics knowledge, plus a document describing other hacks of this nature (say, this FAQ), would have a fighting chance. Knowledge is the key - if you've got enough background information and you think you can get it to work, then you probably *CAN* get it to work, so by all means, go ahead!

Anyways, with "banking" you'll put the code for different games in different sections of a large EPROM, where each section serves as a bank of memory. To select the different banks of larger EPROMs, you'll run a wire to a switch that hardcodes the EPROM's upper address lines to particular values that point to the section of the EPROM corresponding to a given game, and if you have spare positions on the switch you can handle any control panel discrepancies with the switch. Unfortunately, any differences in peripheral boards (like sound boards), memory size, or interrupts are going to be more difficult to handle, since these are differences in the motherboard architecture will hinder the sharability of the motherboard between various game's code.

If you have extra poles on your switch, you can select the use of different hardware or modify things like interrupt handling. If the total length size of the games' code differs, you can avoid have addressing problems, in cases where the sizes of the game code are multiples of a power of two -- place multiple copies of the smaller game's code until you fill a bank equal to the size of the larger game's code. This way, the contents of the upper address lines won't be noticed when the smaller game is playing. The idea behind these types of conversions is that "cheap hacks" are the order of the day. Silicon is cheap these days, but wire is still a pain to wrap, so don't be shy about using lots of EPROM space if it'll simplify the design...

See reference {9.1.4} (Cinematronics conversions) for more details on how a Cinematronics motherboard can be modified to use larger EPROMs that hold several games from that manufacturer. Note that in this case the sound board which is unique to each game presents a problem that can only be overcome by allocating a *LOT* of poles on the switch!

Also, references {9.1.5}, {9.1.6} and {9.1.7} contain examples of this technique as applied to Gravitar and Black Widow, and four older Williams games (Robotron, Joust, Stargate, and an upgraded hack for Bubbles).

One last word on EPROM-hackery. Many games use similar hardware architectures, but protect themselves through the use of custom security chips. Everything from basic PALs and GALs through to some truly exotic beasts have been used. On such games, an EPROM swap will *not* work, no matter how "clean" it may look on paper, because the game depends on the existence of the custom chip to work properly. There's not much you can do under these circumstances; security chips are designed to be unique to a particular game, and are also designed to be extremely difficult to reverse-engineer. While "difficult" does not always imply "impossible", it suffices to say that if you know how to defeat such schemes, you don't need to be reading this FAQ, as you're several miles above the rest of us mere mortals. (Might we suggest the FAQ for misc.legal instead? :-)

"All-in-one", or "Transplanting":

This approach requires a substantial amount of hardware (power supply, new board set, and all auxiliary board and wiring harnesses) and a roomy cabinet to boot, since you're basically transplanting the innards of your new game into another game's cabinet. As you might expect, internal space constraints do tend to limit the number of games you can put into a single cabinet using the "All in one" approach.

This approach centers around combining the video signals coming from several boards at the monitor. Usually, a switch controls which board gets power, and this board will provide the signal to the monitor. If all your boards have the same power requirements, then the power supply can also be shared; you'll switch power to each board individually instead of switching on one of many power supplies.

In the case where the video signals are digital (e.g. the Cinematronics vector games) you only need to feed the inputs from several boards through a multi-input AND gate that has pull-up resistors everywhere. In the analog case (which includes most raster games and other vector games), things are more difficult, since you want to send output from the running board to the monitor, while at the same time disconnecting the powered-off boards from the circuit. Switches come in handy here, but the wiring can still be difficult.

A transplanted system is a lot of work to set up. While a single switch can divert power and video from one set of boards to the other, it takes a lot of hardware and time to create such a setup.

If you've already got the hardware, it's not too bad, but you should also be warned that this method is fairly permanent; once you hack the two (or more!) games into the cabinet, you'll have very little room to work inside, and because of the serious wiring modifications you may have done, you'll be likely to hesitate before changing anything else.

An example of someone who might consider this approach would be someone who just inherited an empty Tempest cabinet that was in horrible physical condition, with deep scratches on the cabinet, water damage, etc., but was otherwise (i.e. electronically) sound. The wiring harness and power supply could be salvaged and transplanted into a Gravitar, Black Widow, or Space Duel cabinet, and they'd get a spare color vector monitor as a bonus.


Conversion Examples

Below are some descriptions of some of the easier conversions. These descriptions aren't supposed to contain every detail needed for the conversion (hey, only the manual is supposed to have all that detail, and besides, FAQ space is limited, just like in your basement!), but they'll give you a general idea of what you'll be doing.

Once you've read through a conversion that can be described in a paragraph or two, we are hoping you'll be tempted to go try it yourself (with the help of the appendices and manuals of the games you intend to convert). We've picked these as fairly simple examples in order to illustrate the principles involved; consult the actual documents if you'd like to understand more.

JAMMA: All JAMMA games <-> All other JAMMA games ("Plug-n-chug")

Swap boards and play. Tough, wasn't it?

The only catch is whether the game was designed with a horizontally-oriented monitor in mind, or a vertically-oriented monitor. Assuming the monitor is the same orientation for the new game in question, you're done. (Unfortunately, no one has yet compiled a list of all vertical and horizontal games that conform to the JAMMA standard, so it's a bit tough to figure out whether it's JAMMA and what orientation the monitor should be, just from the game's title...)

JAMMA doesn't always answer everything - sometimes game designers will cheat, and sometimes JAMMA doesn't have enough pins. Four-player games (Teenage Mutant Ninja Turtles), and multi-button games (SFII) are examples of these situations. The boards are JAMMA, but you need to do a little extra work to get things playable.

Cinematronics: Armor Attack <-> Rip Off ("Plug and chug")

Plugging and chugging isn't limited to new games. If the hardware was suitably designed in the first place, you can do it with many older games too. Suppose we already own an Armor Attack cabinet, but we went shopping last weekend and picked up a Rip Off board set.

If you plug a Rip Off board set in place of an Armor Attack board set, you can simply power up the Armor Attack cabinet and play Rip Off to your hearts content. This is possible because both games use identical control panel inputs. (Of course, you may find the Armor Attack screen overlay rather obtrusive; if so, just remove it before playing Rip Off...)

You may have guessed that this conversion also goes both ways; you can also put an Armor Attack board set into a Rip Off cabinet, though in this case you may have to "guesstimate" the location of the colored sections of the Armor Attack overlay.

See reference {9.1.4} for the full details on all Cinematronics conversions.

Cinematronics: Armor Attack <-> Rip Off ("Banking")

Okay, let's try that same conversion again, but let's assume that we didn't get as lucky when we went shopping, and we don't have a complete board set to work with. Instead, all we managed to find was the sound board.

It just so happens that the Armor Attack program is twice the size of the Rip Off program, so to compensate we'll burn a 2732 with TWO copies of the Rip Off program, making it the same size as your Armor Attack program. Now the motherboard can choose an instruction from either copy of the Rip Off program and it will find the correct instruction it needs to play Rip Off.

Again, because Armor Attack and Rip Off have identical control panels, no changes to the control panel need to be done. The only hardware required is a Rip Off sound board, swapped in place of the one for Armor Attack. (Okay, so you have to flip the diagnostic DIP switch #7 to "ON" for Rip Off, but who's counting?)

Note the main difference here -- instead of swapping whole board sets, you're using the same Armor Attack motherboard in this conversion. This is very handy if you're missing a spare copy of the motherboard in question.

See reference {9.1.4} for the full details on all Cinematronics conversions.

Cinematronics: Adding Star Castle ("Banking" / control panel mod)

Now, if you were to "double up" Star Castle the same way you did with Rip Off, you'd have three games of the same size -- Armor Attack (your original motherboard) and the two (doubled) games, Star Castle and Rip Off. Apart from switching the test-mode DIP switch (#7) again (Rip Off expects it to be ON; Star Castle and Armor Attack expect it to be OFF), there's nothing stopping you from doing the same banking trick again and putting a third game into your cabinet.

This time, you'll need to add some extra wiring to the control panel to compensate for the differences. Hook up the P1 START button to #10 on the control panel's patch panel (located under the control panel), the P1 THRUST button to #6, and P1 FIRE to #8 on the patch panel.

Grab a Star Castle sound board to go with the first two sound boards, and swap away. Three games, one motherboard, one cabinet. (And if you're wondering why Cinematronics didn't use copy-protection, the unique (and almost impossible-to-reproduce) sound boards served the purpose quite well. Unless you were willing to play without sound, the games were "protected" from such copying.

See reference {9.1.4} for the full details on all Cinematronics conversions.

Williams: Robotron to Joust (More "Banking-and-control-panel-hackery")

Both games have identical hardware; only the ROMs change. If you've got the other game's ROM board, you can "plug-and-chug" and be off to the races (after you've hacked the control panel.)

On the other hand, if you don't have the other game's ROM board, you can make do by just burning a new set of chips. In short, rather than swapping boards, swap ROMs directly. Make sure that you use the same type of EPROM (2532 or 2732) as the Robotron originally had. Burn a set of EPROMs with the Joust ROM images and put them in the ROM board. Do the same thing for the sound board's single EPROM, and hook up the control panel. Done.

A more sophisticated approach is to combine the EPROMs into one chip for program ROM, and one for sound ROM. Swap two chips, not thirteen, when you want to swap games. The full hack, along with information on getting Stargate up and running, is documented in reference {9.1.6}. Reference {9.1.7} takes it one step further and shows you how to get Bubbles out of it by upgrading the motherboard.

The optimal approach is to use the hacks described, and "bank" all four games onto one set of chips. This is left as an exercise for the reader. It's not terribly hard to do, but you'll need an EPROM programmer capable of handling very large (256K-by-8, or 2-megabit) EPROMs.

Atari: Asteroids and Asteroids Deluxe ("Adaptor-hack")

This is one of the simplest adaptors to create, especially given that we're talking about an ancient pair of vector games.

Nevertheless, the pinouts between the two games are very similar. By exchanging pins N with 12, P with 13, and S with 15, you're done.

Create an adaptor that connects all pins (except the pins to be swapped) "straight through". If the edge connectors you've chosen for your adaptor are feeling cooperative, you can do this without any wire at all, save that used for the exchanged pins.

However you do it, once you've built (and checked) it, plug one end into your Asteroids (or Asteroids Deluxe) board, and plug the other end into your Asteroids Deluxe (or Asteroids) wiring harness, power things up, and enjoy.

See reference {9.1.1} (Asteroids <-> Asteroids Deluxe) for the full details. References {9.1.8} (Gravitar -> Tempest) and {9.1.9} (Gravitar -> Major Havoc) contain examples of adaptor hacks applied to other games.


Debugging Tips

So, your conversion doesn't work. Bummer, and welcome to the club. This section isn't intended to be a complete guide, but it should serve as a useful checklist for your first stab at making things work. You should also probably check the "Miscellaneous tips" section, as it's got some random tidbits of information that may also prove useful as you try and understand what went wrong.

  • Before you power up, check your wiring. Pay extremely close attention to your power and ground connections; checking them more than once is perfectly fine. On valuable boards, one of our authors has been known to check three times -- anything less than a unanimous "yes, it's perfect", and the power switch doesn't go on.

  • After you power up and it doesn't work, check your wiring. It's amazing how many times you can look at a piece of wire and say "yup, it's in the right place", and still be wrong.

    Trust us on this one.

  • Also check your wiring against "standard" documentation, and if that doesn't work, check it against the hardware itself.

    You may be doing everything "right" according to the document you found on the 'net, but a look at the schematics will highlight an error. This may come as a shock to some, but there have been real incidents in which stuff posted to USENET did, in fact, contain errors. Film at 11.

    Conversely, you may be developing a conversion from scratch, and you'll find errors in the official manufacturer's schematics. These are rare, but they're out there. If there's any doubt, check the hardware itself. Silicon doesn't lie.

    A word on manuals -- there's no "library" of manuals out there, nor will there be. Most manufacturers stop supplying manuals for their games after a few years (Atari is the lone exception; $14 will get you a copy of any manual they've ever made), so the only real sources of docs are whatever you can find when you're out buying, or the archives of other collectors on r.g.v.a.c. Playing librarian isn't a whole lot of fun, but a cheque for $20 or so will still convince most collectors (at least in 1994) to dig through their files and find a copier. Still, it does take time, so if you're working with Atari parts, we recommend you deal with them -- (while there's sometimes a risk that the schematics will be photo-reduced beyond the point of legibility, they've also been known to send original copies if they have a large enough inventory. Ya pays your money and ya takes your chances, but the service is still infinitely better than that offered by other companies...)

  • Regression-test. If you're at a stage where you think that part (even if not all) of the conversion will work, power it up and see what happens. If it works, you've at least got something you can go back to. For instance, when creating a JAMMA adaptor for a game, hook up power and video outputs -- this will tell you whether the game works or not. Once you've got this working, you can worry about sound output and control panel inputs.

    Be careful when regression-testing. If your adaptor doesn't work, and you suspect it may have damaged the board in the process, check the power supply before continuing. If the power supply is damaged, it may also damage any *new* boards you plug into it. The point here is to verify that *all* parts of your system are still in working order before continuing any further.

  • Go backwards. If things stop working, go back to the last point at which things worked, and see if you can't figure out where you might have goofed.

  • Check your assumptions. If you're doing a banking-style conversion and things work for one game (but not another), maybe you misread something on the schematics. Sometimes different games will use the same hardware in different ways; Robotron is an example of a game for which a simplistic address-decoding scheme will work fine, but the same scheme will fail on Joust and Stargate. The assumptions you make for one game may not hold true for others, even if the underlying hardware is practically identical. Diagnostic output from the game's self-test routines can be very useful here.


Miscellaneous Tips

Controls

Buttons:
Buttons are generally grounded on one side, so that the PCB will see the input pulled low when the button is pressed.

Leaf switches and microswitches:
There are two kinds of switches: leaf switches and micro- switches. For most applications, they're interchangeable. Leaf switches have no "clicking" sound when pressed and were common on old games; the newer microswitches make a definite "click" when pressed and are more common on newer games.

Microswitches are more reliable than leaf switches, and also provide a "normally-closed" output (the inverse of the "normal" operation of a leaf switch or microswitch). This output can be put to use as described later.

For normal applications, it doesn't make any difference which kind of switch you use. Some players prefer one over the other; it's this author's experience that one can develop a faster "touch" on a leaf switch (useful for something like Defender), but you lose something in terms of definitive feedback (which would be valuable on a game like Street Fighter).

Digital joysticks:
Digital joysticks are the same as four buttons; instead of pressing buttons with your finger, you press them with the stick.

Analog joysticks:
Analog joysticks are most often potentiometers and springs. The "flight yoke" controllers for Star Wars, Firefox, and STUN Runner, for instance, are all based on 5K pots. Other examples of this type are the analog "thrust control" for Lunar Lander and the steering wheel in Spy Hunter.

Optical joysticks:
The funky "optical joystick" used by Sinistar is a piece of engineering artwork. It's also very rare, and even when it can be found, it's usually very expensive.

It can also be replaced with a conventional (microswitch- based) joystick. Note that it must be a microswitch-based stick to work, as it relies on the use of the "normally- closed" outputs that only a microswitch can provide.

See reference {9.2.1} for more information on Lee Crawford's Sinistar Joystick hack. At $8.00 and some wire, versus $130.00 and a few weeks' wait for mail-order, you might want to give it a try.

Hall-effect joysticks:
These are exotic creatures. If you find any at a bulk buy, and you can get 'em cheap, go for it. They're generally very hard to come by, and can be expensive if you try to purchase directly from the manufacturer.

John Lee writes:

"The Hall Effect is a phenomenon in electronics where a static magnetic field causes a small electrical potential to be created in an electronic device. These devices are available commercially as "Hall Effect sensors" and are used as switches. They work very nicely in environments where things must be sealed, have less moving parts than other switches, and there aren't any electrical contacts to wear or oxidize--just move a magnet near to and away from the sensor to activate and deactivate it. Hall-effect keyboards can work just fine in very dusty, humid, or explosive environments, for instance."

Okay, so that's the digital version. Now for the twist:

"Also, since the effect is more or less linear to the magnetic field strength, a Hall-effect joystick can be continuously variable."

Translation: There is also such a thing as an *analog* Hall-effect joystick.

On this subject, Duncan Brown writes that for "Escape from the Planet of the Robot Monsters", and "I, Robot" (two Atari games known to use an analog Hall-effect joystick), that:

"There is a circuit board for each axis on the bottom of the stick, with a fixed Hall-effect transistor mounted to it. Sliding dangerously close to it is a little rod magnet, moved by the motion of the stick."

The bottom line is that Hall-effect sticks are often a pain to deal with. They're very reliable, but because of their complexity and relatively complicated mode of operation, were never widely used. Since they weren't widely used (and since they were more expensive to construct in the first place), they're fairly rare, and potentially very expensive.

Indeed, the only reason we suggested that you might be able to find them cheaply is because of their rarity -- while rarity often implies value to a collector, their nonstandard nature can also lead operators to discard them as worthless. The logic is similar to that described in reference {9.3.3} (Buying from an Operator FAQ ) with respect to vector monitors. They may be rare and valuable to a collector, but for this very reason, may also have little or no value to an operator.

One final word. Rumor has it that people have managed to hack analog joysticks to replace analog hall effect sticks. If you find any definitive information on this, or (better yet) if you've actually *done* it, post about it to r.g.v.a.c. The world will thank you, and we'll also be able to add more value to this FAQ.

Encoder Wheels (Trakballs, knobs, and steering wheels)
Encoder Wheels are used wherever both the a speed and direction of a freely-rotating object are required for game play. Examples of games that use this technology are any game with a trakball (Missile Command, Centipede) or free-spinning knob (Tempest, Tron), which may often be attached to a steering wheel (Pole Position and many other driving games).

The "encoder wheel" itself is a perforated disc that rotates with the controller. A pair of photosensors generate square- wave outputs as the perforations alternately pass and obstruct light. The end result is two square-wave outputs; a clock (CLK) and a direction (DIR). Each clock pulse denotes a certain degree of rotation, and the photocells are spaced (in accordance with the size of the holes in the wheel) such that the two waves will be 90 degrees out of phase, the value of the "direction" wave can then be used to determine whether the detected rotation occurred to the right or to the left.

A free-spinning knob requires one encoder wheel. A trakball requires two such wheels which are rotated by the ball's movement. One wheel measures vertical movement, and the other measures horizontal movement, producing four output signals.

Power Supplies

Isolation transformers:
These aren't really power supplies, but they're an important safety feature. If your monitor says "ISOLATION TRANSFORMER MUST BE USED", take their advice and use one. Chances are almost certain that if you purchased your cabinet in working order, it'll have one already set up.

BUT... Suppose you purchased your monitor separately. Perhaps you found a nice 15" raster monitor from an old cocktail machine during a bulk buy, and you figure it would make a nice piece for your workbench. Or you found a whole pile of monitors that the operator "just wants to clear out". In these cases, you may not be able to tell whether or not you need one. If this is the case, play safe and assume you need it anyway.

Okay, great. Isolation transformers are Good Things, but what the heck *are* they, and why do we want to use them?

An isolation transformer is a safety device that goes between the 120V AC coming out of the wall and the monitor. They're often found between the 120V AC from the wall and the game's onboard power supply, but can also sometimes found between the game's power supply and the monitor. The key thing is that they always go between the 120V AC from the wall and the monitor; this is how most games are wired -- only the monitor AC goes through the isolation transformer.

To understand why, we'll have to learn a bit about how your home is wired...

The average North American house has a center-tapped 240V AC signal coming in from the outside world. The center tap is connected to earth ground at the power distribution box. Ground (the green wire) is connected to this center tap through the third wire (safety ground). To get 120V AC, you connect (at the distribution box), a white wire (neutral) to the ground or center tap, and the black wire (hot) to either of the 120V AC terminals. All green and white wires are therefore electrically the same at the distribution box. (The difference is that the white wire is intended to carry current, and the green one isn't - any current in the green wire indicates a fault...)

A monitor has a "hot chassis". AC comes into the monitor, and one side is connected to the chassis through the diodes in the monitor's AC->DC rectifier. Through these diodes, you have a connection to 120V AC. Grabbing such a monitor with bare feet on a concrete floor isn't going to be a pleasant experience.

This is where isolation transformers come in. They're a 1:1 transformer that keeps the game's electrical GND away from the wall's GND. *Neither* of the output wires from the isolation transformer has any electrical connection relationship to the green GND wire; i.e. earth ground. Theoretically, you should be able to hold either of these wires in one hand and ground yourself with the other and remain safe. (We don't recommend it due to real-world factors such as leakage -- we're just trying to illustrate the point)

Without such a transformer, this isn't so. And we've already talked about the hot chassis, meaning that a game without an isolation transformer may have a very different idea of GND than you do. When you engage in philosophical discussions with your machine on the definition of GND, you'll discover that the game tends to win the argument, usually ending the conversation with a nasty shock.

That's bad enough, but if your hands happen to be tightly wrapped around a joystick at the time, and your muscles cramp as a result of the shock, you will find it *very* difficult to release your grip; muscles work on electrical impulses, and unless your nerves can put out 120V AC to override the game's output, or you can move your *other* muscles to knock your tightly-gripped hands off the controls, the next "cabinet" you work on may be a pine box.

We say again:

If the monitor says it needs an isolation transformer, *OR* if you're not sure -- GET ONE AND INSTALL IT BEFORE POWERING UP.

Grounding - another safety tidbit:
Games are meant to be plugged into grounded outlets. If you check your house wiring (and live in North America), you'll see that the white wire ("neutral") is connected back to the same place as the third prong ("safety ground"), while the 120V is supplied on the black wire ("hot"). The black wire carries a 120V sine wave centered around (i.e. goes 60V above and 60V below) the white wire, which is the same as ground.

Okay, so if your game grounds its chassis to the white wire, or rather, what it *thinks* is going to be the white wire when it's plugged in... Imagine a mis-wired socket, or a two-prong plug, that gets plugged in the wrong way. Sit this machine next to a properly-wired device. Now touch both devices at once. Your next of kin will finish reading this FAQ for you.

The moral:

Use a properly-grounded outlet -- and a properly-grounded plug. This is just basic electrical safety, but you only have to make one mistake; in the arcade of life, you start with one life and you don't get any bonuses at 10,000 points.

Switching versus linear:
A linear power supply has a large transformer that takes the 120V AC signal from the wall and converts it to a lower AC voltage. It passes this lower voltage through a rectifier, which will give you DC. The DC won't be flat or steady, but at least you're halfway there. The DC is then passed through a filter to smooth it out, and then a voltage regulator to obtain the exact voltage.

All of these steps, when taken together, require a lot of power; you're effectively converting excess energy into heat. The transformers tend to be extremely bulky, and more often than not, rather expensive.

Whenever possible, use a switching power supply. They're not only cheaper and lighter than their old linear counterparts, they're also more reliable and produce a cleaner supply for your game. Can't find one cheaply? Rip apart an old IBM PC and use its power supply. It will supply everything you need for running the average board.

Hacking boards with weird power requirements:
It's often a good idea to modify a board with strange power requirements or a strange sync, so that you can use your existing switching power supply and/or monitor. Don't modify the cabinet - modify the board since it makes future conversions/board swaps easier. Yes, this goes against our earlier advice of being nice to your boards, so let's just say it's a judgement call. It depends on your taste, your ability, and the odds that you might want to sell or trade the board away in the future.

If you're dealing with weird power requirements as in, say, Pacman boards, which convert 7.5V AC; (yes, Seven-and-a-half Volts of Alternating Current, which gets stepped down from a linear power supply earlier in the cabinet -- see what we mean about linear power supplies being potential pains in the butt?) into +5V DC on the board, you're pretty safe to modify the board, as you won't be seeing many situations where 7.5V AC is supplied.

If it comes time to sell the board, you'll have a much easier time making the sale if it can use "standard" power requirements. In the case of Pacman, the modification (which involves only five jumpers) is also easily reversible, which is a bonus, just in case you should be selling it to someone with an original Pacman cabinet someday.

If, on the other hand, you're just dealing with something like pins in different places, but normal voltages, it's probably best to build an external adaptor and include it between the board and the wiring harness. This way, you don't run the risk of damaging the board by making a mistake, and a future buyer of your board won't have to "unfix" it at a later date.

Meanwhile, the Pacman modification is as follows:

  1. Jumper four wires over the AC->DC rectifier diodes (D3, D4, D7, and D8). The idea is to short 'em out; you won't be using them.
  2. Jumper a fifth wire across the large 4-ohm resistor by the heat sink.
  3. Pacman's 7.5V AC pin gets connected to +5V DC from the power supply.
  4. Pacman's GND pin (from the center tap of the 7.5V AC signal) gets connected to GND from the power supply.
  5. Pacman's 12V AC pin gets connected to +12 V DC from the power supply.

Ignoring weird power supply requirements in the first place:
With the appropriate modification, almost any board with oddball power requirements (like the +25V Atari used to store high scores in the non-volatile RAM on older games like Centipede) can be powered by a standard switching power supply with +5V, -5V and +12V.

For instance, ignoring the +25V in the example above will still result in a playable game; only the behavior of the high score table will be affected. If you can live without such functions (or provide the same functions, say with an external sound amplifier), then you can forget about these oddball voltages. Sometimes, lower DC voltages can often make good substitutions for odd voltages. For instance, Williams sound boards "require" a -12V DC signal, but you can get away with a more standard -5V DC signal instead.

NOTES:
If you are applying a voltage to a board that's not specified in the manual as the correct voltage, then you *are* taking a risk that might fry your board. Be *VERY* careful as you try to substitute different voltages/circuits in an attempt to avoid using an oddball voltage, and make sure you understand (using the schematics and your knowledge of electronics) what the board is trying to do with that oddball voltage before you start.

Another example of applying a little understanding to a problem would be the Pacman modification discussed above. Elsewhere on the board, a 12V AC signal is used to generate +16V DC for the audio circuitry. A look at the schematic reveals that the audio op-amps are the only place where the +16V DC is used, and a databook tells you that the chips in question can also be powered with +12V DC. Since you *know* what the board wants and what it can handle, you can use this to design your workaround. This is part of the reason why the hack to Pacman discussed above allows you to get away without using the original Midway power supply.

In an interesting twist of fate, and an example of how various manufacturers "borrowed" from each other during the industry's early days, note that Sega's "Super Moon Cresta" uses exactly the same power scheme as does Midway's "Pacman". Same hack to convert to DC, same power and video pins, same bloody *PARTS* in the same *LOCATIONS* on the board, etc... So if you get a sense of deja vu when hacking on an old board, don't ignore it. You probably *have* seen it before.

Geographical considerations:
In North America, the power that comes out of your wall socket is 120V AC. This assumption does *not* hold true for Europe, where 240V AC is the norm.

Some power supplies have little switches on them to switch between 120V AC and 240V AC inputs. Others (Atari linear power supplies in particular) have "voltage selection plugs" that can be used for the same purpose.

If you don't know what type of power your power supply expects, and especially if you've received parts from overseas, take a few minutes to check.

Monitors

Horizontal versus vertical:
Don't bother rotating a monitor from vertical to horizontal (or vice versa). Just buy another cabinet with a monitor oriented the correct way. You'll save yourself a lot of headaches (and back pain) in the long run.

There are two exceptions to this rule: Sega's "convert-a- cabinet" system (used on their vector games) included slots to allow the monitor to be removed and rotated easily, and some of the new higher-end JAMMA cabinets, which have a swivelling monitor which can be rotated from horizontal to vertical without having to remove it.

Actually, there's one other exception. Don't use a cabinet! If you're not worried about appearance, your setup can be as simple as a power supply, harness, joystick, and monitor on a workbench. Rotating the monitor in this kind of a situation is a piece of cake :-)

Swapping outputs to rotate:
It's possible to avoid the problem of rotating monitors with vector games; you can put the vertically-oriented Tempest in any other Atari color vector cabinet, which will be horizontally-oriented. You can sometimes swap the X and Y outputs on the Tempest board and shrink the dimensions with the adjustments on the game board to get it playing on a horizontally mounted monitor. Some monitors (and some Tempests :-) seem to cooperate, and some won't. Give it a try and see what comes out.

Alas, this trick only works because the game has a vector display. There is *NO* way to "swap and shrink" the signals meant for a raster display. Sorry.

Vector monitors and power supplies:
Atari B/W vector monitors want a 60V AC power supply. Atari color vector monitors want a 50V AC power supply. Yes, sixty for one, and fifty for the other. (We don't make the rules, we just follow 'em...)

The bottom line is that you *CANNOT* swap power supplies from a B/W vector game cabinet into a color one. Don't try. Since the power supplies look identical, this can be a real problem. If there's any doubt about which is which, disconnect the power supply, turn it on, and measure the voltage at the source.

Most vector monitors from one manufacturer are incompatible with games from other manufacturers. One notable exception to this rule is Omega Race, which uses a monitor identical to the ones used in all of Atari's B/W vector games.

Pinouts

JAMMA:
The JAMMA standard was invented in 1985; any game older than this will not be JAMMA. For reference, here is the JAMMA pinout:

 ---------------------------------------------------------
   Solder Side            |          Parts Side
 -------------------------+-------------------------------
       GND            | A | 1 |          GND               
       GND            | B | 2 |          GND
       +5V            | C | 3 |          +5V
       +5V            | D | 4 |          +5V
       -5V            | E | 5 |          -5V
       +12V           | F | 6 |          +12V
      - KEY -         | H | 7 |         - KEY -
   Coin Counter #2    | J | 8 |      Coin Counter #1
   Lock Out Coil #2   | K | 9 |      Lock Out Coil #1
   Speaker (-)        | L | 10|      Speaker (+)
                      | M | 11|        
   Video Green        | N | 12|      Video Red
   Video Sync         | P | 13|      Video Blue   
   Service Switch     | R | 14|      Video GND    
   Tilt Switch        | S | 15|      Test Switch
   Coin Switch #2     | T | 16|      Coin Switch #1
   2P  Start          | U | 17|      1P  Start          
   2P  Up             | V | 18|      1P  Up
   2P  Down           | W | 19|      1P  Down         
   2P  Left           | X | 20|      1P  Left
   2P  Right          | Y | 21|      1P  Right
   2P  Button 1       | Z | 22|      1P  Button 1
   2P  Button 2       | a | 23|      1P  Button 2
   2P  Button 3       | b | 24|      1P  Button 3        
                      | c | 25|         
                      | d | 26|             
       GND            | e | 27|          GND  
       GND            | f | 28|          GND  
----------------------------------------------------------

Konami:
We're also including the Konami standard pinout, as it was also used on many games by many different manufacturers.

 --------------------------------------------------------
   Solder Side            |          Parts Side
 -------------------------+------------------------------
       -5V            | A | 1 |         +12V
   Speaker            | B | 2 |      Speaker
   2P  Button 2       | C | 3 |      2P  Button 1
   2P  Left           | D | 4 |      2P  Right
   1P  Start          | E | 5 |      2P  Start
   1P  Button 2       | F | 6 |      2P  Up
   1P  Button 1       | H | 7 |      Service Switch
   1P  Right          | J | 8 |      1P  Left
   1P  Up             | K | 9 |      2P  Down
   Coin  (1)          | L | 10|      Coin  (2)
   1P  Down           | M | 11|      Coin Counter #1 
   1P  Button 3       | N | 12|      Coin Counter #2 
   Video Green        | P | 13|      Video Blue
   Video Red          | R | 14|      Video Sync
                      | S | 15|
       GND            | T | 16|          GND
       GND            | U | 17|          GND
       +5V            | V | 18|          +5V
 ------------------------------------------------------

Identifying pinouts:
Identifying pinouts of unknown boards can be difficult. We offer the following approach:

  1. Do you already have a copy of the game's pinout? If so, you're done. (Make sure you've got the *right* copy of the game's pinouts. Moon Cresta, for instance, was made by at least four different manufacturers, three of whom used different pinouts...)

  2. Is the manufacturer shown? If so, who are they, and do you have any copies of pinouts by the same manufacturer? If so, compare them; do they "make sense" if you try them against the method outlined in steps 4-8) below?

  3. If it's a Japanese name, and a fairly new board, and it's got a 56-pin connector, it's probably JAMMA. Still, it always pays to double-check before you plug something in based on your assumptions. There *ARE* 56-pin connectors which aren't JAMMA, so the double-check is still important.

  4. Okay, now you're desperate :-) Get a list of all the pinouts that you *DO* know.

  5. Eliminate any pinouts with connectors that don't match the board in question.

  6. Look at telltale markers, like the power pins; you should be able to identify +5V and GND fairly easily by tracing backwards from some TTL chips. Using this, and the number of pins on the connector, should allow you to eliminate a few more pinouts.

  7. With the few pinouts you have left, look for audio and video pins. These are generally grouped together; two pins going to the same location (often a heat-sinked audio amplifier chip) will probably be audio, and four pins, three of which go to one chip and a fourth of which goes to a nearby chip, will likely be video. Large groupings of pins that go through resistors and/or diodes will likely be control input pins.

  8. *NOW* do you have a match? If so, start "experimenting"; make a few assumptions and try powering the board up without any video or controls connected and "experiment" by looking for fluctuating signals (characteristic of video or audio) on the pins. This is a fairly involved process, but can be simplified greatly by use of a partially- constructed adaptor to your current wiring harness. (Indeed, this is one of the reasons adaptors are fairly popular; they often get created through the process of determining the pinout from an otherwise unknown board)

    Note that this can be something of a risky procedure if you don't know what you're doing. For your first few times, you may want to do everything except powering up the board: write down your best guesses, describe the board, and ask the 'net if anyone out there recognizes it and knows the pinouts. You might just get lucky, and if your guesses were right, you'll give your self-confidence a great boost.

    Rick Schieve has written an excellent text file on this subject; see reference {9.3.4} for details. John Keay has another method for quickly identifying and recording pinout information; see reference {9.3.5} for details.

Unused connectors:
If there are empty connectors on the board, don't panic. Some boards have "test connectors" that are unused during normal use. If you don't know whether a certain board or board set is complete, ask the 'net if anyone knows "how many boards and connectors were used in XYZ".

Adaptors:

Jammatization:
Adaptors are one of the easiest and cheapest approaches to doing conversions; this is why JAMMA cabinets are so popular among collectors, even among those of us who prefer "classic" games. Large collectors will often accumulate a series of adaptors for their games, all of which convert to a standard pinout, usually JAMMA. Although the process is the same as building any other type of adaptor, the "random-raster-game to JAMMA" conversion is so common that it has become known colloquially as "Jammatization".

Construction techniques:
There are two main approaches to adaptor construction. The "right" approach for you will depend on what set of parts you can most easily replace.

Both approaches involve an XX-pin (female, and "XX" depends on the board in question) edge connector for the non-JAMMA board and a 56-pin "finger board" (a straight piece of PCB, also known as a "male-to-male" connector), and a 56-pin (female) edge connector for the JAMMA side.

  1. Skip the 56-pin connector and solder the wires directly from the XX-pin connector to the finger board. The resulting finger board end of the adaptor can be plugged directly into your JAMMA harness. You'll use one finger board per adaptor.

    The end result would look something like this:

            --------< <---------->~~~~~\/~~~~~~~~~~------<
    TO      --------< <---------->~~~~~'\/~~~~~~~~~------<  DIG
    JAMMA   --------< <---------->~~~~~~'\/~~~~~~~~------<  DUG
    WIRING  --------< <---------->~~~~~~~'`~~~~~~~~------<  PCB
    HARNESS --------< <---------->       /~~~~~~~~~------<
            --------< <---------->~~~~~~'    
             56-pin     male-male  Wires that map  44-pin
             female     PCB with   JAMMA pinouts   female
             edge       straight   to 44-pin Dig   edge
             connector  traces     Dug pinout.     connector
    
    
    Alternatively...

  2. Instead of soldering the wires to the finger board, solder the wires from the XX-pin connector to a 56-pin connector. Plug one end of the finger board into the 56-pin connector, and the other end into your JAMMA harness.

    Rather than using a finger board for each adaptor, you're using one 56-pin connector per adaptor, as the finger board can be used between different adaptors.

    The end result was shown in section {5.3}, but is reproduced here for quick reference.

            -------< <----------> >---------~~~~~\/~~~~~~~~~------<
    TO      -------< <----------> >---------~~~~~'\/~~~~~~~~------< DIG
    JAMMA   -------< <----------> >---------~~~~~~'\/~~~~~~~------< DUG
    WIRING  -------< <----------> >---------~~~~~~~'`~~~~~~~------< PCB
    HARNESS -------< <----------> >---------       /~~~~~~~~------<
            -------< <----------> >---------~~~~~~'    
             56-pin    male-male   56-pin    Wires that map  44-pin
             female    PCB with    female    JAMMA pinouts   female
             edge      straight    edge      to 44-pin Dig   edge
             connector traces      connector Dug pinout.     connector
    
    
    Like we said right at the introduction, the "right" approach for you depends on your resources; this is a perfect example. If you live near a surplus store that has 56-pin female edge connectors for $1.00 apiece, but you only have a few finger boards, grab a big pile of connectors go with method 2. If it's easier to use mail-order, and finger boards are half the price of edge connectors, get a big pile of finger boards and go with method 1.

RGB, Sync, polarity, and all that rot. (Stupid Video Tricks, Part I)

The Basics:
Rick Schieve has written a text file on raster video basics; check out reference {9.3.6} (Raster Monitors) in the bibliography for more information, but we'll summarize the high points here:

All raster monitors use generally the same set of inputs: RGB, and some form of sync. RGB stands for "Red, Green, and Blue", and denotes the colors of the beams. Sync is for "synchronization", the process by which the electron beam in a raster monitor sweeps across the screen.

(You may have heard the terms "horizontal", "vertical", and "composite" sync. For now, just consider "horizontal" sync to be the sync pulse at the end of each line on the screen, the "vertical" sync to be the pulse at the end of each screenful of data, and "composite" sync to be a magical combination of both. We'll get into the gory details soon enough :-)

So far, so good, right?

Wrong. While all these signals are common to raster games, they come in different (and alas, incompatible) flavors. Working around these difficulties can be one of the more confusing problems for someone doing conversions. That's where this FAQ comes in. We'll try and describe the common variants, and give a few examples of games that use them. You should be able to extend the approach to other games.

RGB polarity
While all raster monitors accept RGB inputs, they can have either positive or negative logic. The majority of games use positive logic (when the voltage is on, the electron gun turns on, and you get a bright image), but Nintendo games use negative logic, which works the other way around.

RGB signals are analog signals; you'll need an analog inverter to get around the problem; a CMOS hex inverter (say, a 4069), which is designed to invert digital signals, won't work. To be more precise, it theoretically *shouldn't* work, but on the practical side, a few people have tried it and actually managed to make it work. Your mileage may vary. One tip: if you try this, make sure you ground all of your unused inputs.

Meanwhile, the "right way" is to use an analog inversion circuit for each of the three RGB signals. It requires a +12V, -12V, and -5V supply, but some power supplies will supply all three voltages. Thanks to Paul Kahler for the original schematic and document (see reference {9.2.2}).


                              R3
                       +-----/\/\/---------+
                       |                   |
                       |     |\   +-- +12V |
             R1        |     |  \ |        |
Input ------/\/\/------+-----|-   \        |
                       |     |LM318 \______|_______ Output
-5V --------/\/\/------+  +--|+    /
             R2           |  |   /|
                          |  | /  |
                          |       +--  -12V
                          GND
       
R1, R2, and R3 are all identical resistors.  A value of roughly
10K should provide good results.  The LM318 is a high-frequency
op-amp.  Its pinouts are as follows:

                       1 Comp/bal     8 Comp
                       2 -in          7 V+
                       3 +in          6 output
                       4 V-           5 Comp/bal

The "Comp" pins may be ignored.  An LF356 might also work, but
the 741 is not recommended.

Sync polarity:
Now that we can generate the RGB signals our monitor requires, we still have to put the signals on the screen in an orderly fashion. The is what the "sync" signals are for.

Again, we run into the problem that some boards produce negative sync, and some don't. Fortunately, since all sync signals are digital, the process is much simpler; using a *really* fast CMOS hex inverter is a perfectly legitimate way around the problem. A TTL inverter should also work; all sync signals generally operate at TTL levels. Still, this is dicey business, so your mileage may still vary.

Composite versus Separate Sync:
Now that you know how to invert syncs, you're ready for the last bit - the two flavors of syncs and how to mix and match them.

Older monitors often had separate sync inputs; one for horizontal sync (the retracing of the beam across the screen), and one for vertical sync (the return of the beam from the bottom of the screen to the top of the screen).

Newer games (but also many older ones) used monitors which accepted composite sync; the two signals were combined together on the board, and a bit of circuitry in the monitor determines whether a given sync pulse is a horizontal or vertical retrace.

If you have an older game that outputs separate syncs, and a newer monitor that can only accept composite sync, you can combine the two using digital logic. Simply "OR" the two signals together with a TTL chip to obtain the composite sync signal.

Since both composite and separate syncs can be positive or negative, it may be necessary to invert the composite sync signal after the ORing stage. If this is the case, just use a NOR gate instead.

Sync shortcuts:
If you've got schematics for your games, take a closer look at them. The game's wiring harness may show separate syncs, but the schematic itself may show that there are unused pins for composite sync. All the old Williams games (Defender, Stargate, Joust, Robotron, etc...) are like this, as is Atari's Missile Command.

A little schematic-browsing can make your life much easier.

One last cheat -- if your monitor only supports separate sync, you may be able to get away with connecting a composite sync signal to either the horizontal input or to both inputs. No guarantees, but you might as well try it as a "first shot".

Inversion. (Stupid Video Tricks, part II)

Smoke and mirrors:
Some games have mirrors in the cabinets which reflect the video output. This is great, if you're playing Asteroids Deluxe in the original cabinet. This sucks, however, if you're trying to put an Asteroids Deluxe boards in a conventional Asteroids cabinet. Most of these games have pins on their edge connectors for X- and Y-inversion; pulling these pins high (+5V) or low (GND) will invert the image in the appropriate axis. Play around until you've got something that looks right on your screen.

Cocktails, anyone?
To further complicate things, some games have "cocktail" pins, which are pulled high or low depending on the wiring harness. On upright games, the signal on the "cocktail" pin tells the game *not* to invert the image when player 2 is up. On cocktail machines, the signal tells the game *to* invert player 2's image.

Finally, and this is the *really* weird one, some games use both approaches -- a PLAYER1 and a PLAYER2 pin, for instance, were used on the Asteroids cocktail machine, both to activate and de-activate the two players' control panels, but also to control video inversion.

Our point here is not to confuse - merely to say that if the game appears upside-down or backwards for no apparent reason, you should probably take a closer look at the pinouts. It's amazing the number of variations that are out there, and it's sometimes a miracle that things show up correctly at all! Again, our earlier rule of thumb applies: If you don't like what you see, play with it until you do.

As a last shot - sometimes it's not on the pins at all. More recent games control their "cocktail" versus "upright" behavior by means of a DIP switch setting. Fiddle with these if you think you've tried *everything*...

It's *STILL* upside-down!
Finally, with vertically-mounted games, there are no guarantees. Some manufacturers believed that a monitor should be rotated 90 degrees to the right, and some believed it should be rotated 90 degrees to the left. So you're not the only person who's confused. The whole industry was confused at one time or another, and this is the historical result.

What this means is that if you've tried all of the above techniques, and you've got a game designed for a vertically- mounted monitor, you may be out of luck. The manufacturer of that game used the same monitor, but they turned it the other way around.

You can get around this by reversing the wires to the deflection coils on the neck of the monitor (and if you're really fancy, installing a switch to go back and forth whenever you like), but like most monitor work, this is a fairly advanced modification, and we recommend that you be absolutely certain that you know what you're doing before you try this.

Remember, monitor hacking can be a dangerous sport unless you know what you're doing and take proper safety precautions. Keep in mind that with all the space you've saved doing conversions, you can probably squeeze in another cabinet. Replacing *yourself* is much more difficult. If you've never hacked on a monitor before, ask some folks on the 'net about proper safety procedures (such as discharging the tube, etc.) before you begin.

Memories...

EPROMs:
EPROMs are Erasable-Programmable Read-Only Memory chips. They are the primary means of storing game program data. You'll often see people "looking for EPROMs", particularly if their machine isn't working.

EPROM programmers are devices used for (surprise!) programming EPROMs. They are also referred to as "burners", as the process involves "zapping" the memory cells with high voltages in order to get them to change state to store the data.

EPROM erasers generate concentrated UV light and shine it through the little glass window onto the chip; the exposure to the UV light is what erases the data. EPROMs are often covered with small sickers; the idea isn't just to put a label on the chip, but to prevent stray light from outside (which may contain some UV radiation at the proper frequency) from hitting the chip -- it may take several days or weeks of bright sunlight to completely erase a whole chip, but it only takes one erased bit to render a video game inoperative.

Owning an EPROM programmer and eraser is a Good Thing. If you get a new game, you can read in the EPROMs and store their data on your PC. If an EPROM dies at any time in the future, you can get a new one (or erase the old one and try to re-use it) and program it with the data you archived. Several programmers exist for the IBM PC; these cost roughly $100-$200. EPROM erasers cost roughly $50-$100.

PROMs:
PROMs are Programmable Read-Only Memories. The key is that they're programmable, but *not* erasable. They're programmed by applying voltages similar to those used in EPROM programming, but they work by blowing tiny fuses on the chip itself; once you've programmed a PROM, there's no way to erase it and reuse it. Once a PROM fails, it has to be replaced.

PROMs can be much simpler and faster (electronically-speaking) than EPROMs, which is why you'll often see very small PROMs on games -- 14-pin chips that hold a few hundred bytes of data needed for the circuitry to work properly, etc...

Programmers that will handle PROMs and other types of programmable logic are more expensive than simple PC-based EPROM programmers; check with an electronics supply house for pricing, which should be in the $400-$800 range, depending on what you need. Yes, this is outside the price range of most video game collectors, and yes, a simple EPROM programmer will suffice for most of your needs, so if you're looking at investing in a high-end programmer, make sure you know you need it first :-)

RAMs:
RAMs hold Random Access Memory. This is primarily used for such things as the state of the screen, the position of the enemy aliens, and your current score. There isn't much to say about RAM, other than that when it fails, you need to replace it, and that parts for older games are becoming more expensive as time goes by.

If you're ever in a surplus store and you see an old motherboard (be it from an arcade machine or not) that's full of RAM chips, and you know you've got a game that uses the same type of chip, do yourself a favor and pick it up if the price is right. You can often get 20-30 chips for the price of one. Removing the chips from the board is often difficult, but at a 97% discount, it's worth the time.

NOVRAMs, EAROMs, CMOS RAM, ZRAM, and other exotic beasts:
Some games keep track of information even when the power is turned off. NOVRAMs (NOn-Volatile RAMs), EAROMs (Electronically-Erasable ROMs), and CMOS RAM (Complimentary Metal Oxide Semiconductor RAM) are popular technologies with older (and some newer) games. A new technology, ZRAM (ZeroPower(tm) RAM), has also emerged in the past few years.

Some of these technologies require weird voltages, which is why some games require weird voltages. For instance, NOVRAMs and EAROMs (used in many Atari games) may be read at +5V, but written at +25V. You can play the game at normal voltages, but the all-time high scores will not be preserved.

Old Williams games used CMOS RAM powered by batteries on the main board. When the power is turned off, the RAM draws tiny amounts of power from the batteries to keep itself alive. We mention this here because one of the most common "horror stories" with such games is for the boards to be thrown into storage with the batteries still mounted. Five years later, when *you* come on the scene, you find the board of your dreams, only to find a mass of corroded metal where the batteries once were.

The solution to a collector is simple; wire up an external battery pack to the original setup, keeping the batteries *AWAY* from the main board. If the batteries fail, your boards will remain safe.

ZRAM is neat. Fed up with all the hassles of batteries, a genius at an electronics firm decided to include the battery with the RAM chip. The resulting product was called ZeroPower RAM, or ZRAM for short. The specifications for one such chip, the 48Z02, claim that the lifetime of the battery is solely dependent on the temperature -- an average chip will have a battery lifetime of 20 years at 70 degrees C, and 99% of chips will have a lifetime of 11 years at 70 degrees C.

An example of a hack that uses ZRAMs in a modern video game is John Keay's hack which allows a Battlezone machine to keep track of its high scores. See reference {9.2.3} for details.

Cabinet Maintenance:

Refurbishing control panels:
In the rush to get the power supplies, boards, monitors, and other stuff working, you may end up neglecting some basic woodworking and/or metalworking tasks. Take a few moments and work on the control panel; you're putting this game on display for yourself, and it should look as good as you can reasonably make it. A former operator shared a quick guide to fixing up control panels:

  1. Completely strip the front panel and remove it. This may also involve removing bits and pieces of the old plastic artwork that covered it.

  2. Depending on the requirements for the new control panel, drill out whatever holes you require. Try to do this with an eye to reusing as many of the old holes as possible. The cheap hole-saw sets found in hardware stores for $5-6 can be great for this task, but if you have a real screw punch, go ahead and use it.

  3. Once all the holes are drilled (including any mounting holes for the bolts that will attach large items like joysticks and flight controls), cut a piece of clear plexiglass to the same size as the largest flat piece of the control panel. Duplicate the panel holes in the plexiglass.

  4. Cover the metal control panel with some attractive plastic artwork. Affix any button labels or instruction sheets to the plastic. If there are any unused holes in the metal, the artwork will cover them, and the plexiglass will protect them from being accidentally poked out.

  5. Generic artwork is available in large sheets from most arcade suppliers, but the original decals for classic games have become extremely rare over the years.

  6. Mount the joysticks and buttons, putting them through the plexiglass and into the control panel. Attach any necessary carriage bolts to hold the thing together.

  7. Solder the leads to the controls, and you're done.


Bibliography

Numerous folks have contributed to the Conversion FAQ by providing detailed conversions to show the reader the different approaches in action.

Please consider carefully before contacting these authors, as plenty of folks try these conversions every year. If they all contacted the author whenever they had trouble, the author would have very little time to work on his/her *own* collection, let alone write up new conversion material.

Simply put, take the time (and we mean *your* time :-) to figure out what went wrong before running to the authors. Start by trying to get the original pinout/schematic info. If you still can't figure out what happened, describe your problem in a post on r.g.v.a.c., and see if someone else responds. They may see something in your description that you didn't, or remind you of something you forgot.

If that still doesn't help, the authors will be much more inclined to help you debug things now that you've gone through most of the "easy" stuff yourself, because by this time, you may have found a real *bug* in their docs, and they'll be just as eager as you are to solve the problem. If an author's e-mail address isn't included in their conversion document, consult their VAPS entry for contact information.

Okay, you asked for it, you got it. Here's a list of all the conversions (as of this writing) on the 'net. We also include a few handy hacks, and a whole mess of reference material. If you build your own conversion and/or write up some material of your own and want to tell the world about it, then please do so!

Everything listed under section {9.1} , "Conversions", appears on the stormaster.com FTP site.

The directory structure may be modified from time to time, but you should still be able to find the conversion you're looking for. Most of the other material is also available at stormaster.com; please check there first before requesting a copy from the authors.

 
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