Conversion of a Williams game to JAMMA is not exactly simple, nor is it complex. Most conversions consist of merely the cables, a few switches to access the setup and test menus and a volume pot. If you follow this illustrated guide you should easily be able to get your Williams game up and running in a JAMMA cab in just a few hours. This document aims give you all the information you need to convert a Williams boardset, finishing with an Example Robotron to JAMMA Conversion. This article applies only to original Williams Defender, Stargate, Robotron, Joust, Sinistar and Bubbles video games and assumes that your boards are compatible and working properly. You can identify you boards on my Williams Hardware Identification and Compatibility Page.

All the connectors used on Williams boards are designated with a three-letter code, for example the power connector on the CPU is 1J1. The first '1' meaning the CPU, the 'J' meaning it is the male connector on the board (which will mate with female connector 1P1) and the second '1' meaning that it is the first connector on the CPU board. All connectors will be referred to using this method.

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The CPU, ROM and Sound boards all need various voltages to power them. The interface board and the Sinistar speech board do not need power as they obtain it through their ribbon cable, though the inputs to the interface board will need grounding, but that will be covered in the controls section. If you wish to replace the Williams PSU in your game with a modern switching PSU, this part of the JAMMA conversion is all you need.

1J1	Early Series Defender CPU Board Click to Enlarge		1J1	Later Series Defender CPU Board Click to Enlarge
1J1	A typical CPU Board for other games (layout may vary slightly depending on revision) Click to Enlarge			CPU Board Power Connector 1J1 All Board Types Pin Connection Notes 9 -5v DC Top 8 +12v DC Unregulated DC 7 +5v DC   6 +5v DC Not connected on factory harness 5 +12v DC   4 Key No Connection - pin removed 3 Ground   2 Ground   1 Ground Bottom, Not connected on factory harness

2J2

Early Defender ROM Board Click to Enlarge

2J2

Later Defender ROM Board Click to Enlarge

2J2

Stargate ROM Board Click to Enlarge

ROM Board Power Connector 2J2 Defender and Stargate Pin Connection Notes 4 +5v DC Top 3 Key   2 No Connection   1 Ground Bottom

2J2

Robotron/Joust ROM Board Click to Enlarge

2J2

Sinistar ROM Board Click to Enlarge

ROM Board Power Connector 2J2 Robotron, Joust, Sinistar and Bubbles Pin Connection Notes 6 No Connection Top 5 No Connection   4 +5v DC   3 Key   2 No Connection   1 Ground Bottom

Click to Enlarge D8224 Sound Board (all games)		Sound Board Power Connector 10J1 Pin Connection Notes 9 No Connection Right 8 -5v DC -12v DC if using Williams PSU 7 Key   6 No Connection   5 Ground   4 No Connection   3 No Connection   2 +12v DC   1 No Connection Bottom
10J1

The Video wiring is the most difficult part of a Williams to JAMMA conversion. The Manuals state that the boards only output Vertical (Vsync) and Horizontal (Hsync) sync pulses with positive polarity, yet a true JAMMA monitor requires negative composite (Csync). However, in most cases we are lucky, as all boards except for early Defenders have positive Csync available. This can either be inverted or a simple modification can be carried out to give you the required negative Csync.

Early Series Defender Composite Sync Circuit

Since we now have the means to make JAMMA friendly Csync on our early series CPU, all we need to do is wire the connector up as shown in the diagrams below:

1J3

Early Series Defender CPU Board Click to Enlarge

CPU Board Video Connector 1J3 Early Series Defender Boards Pin Connection Notes 7 Key Top 6 Horizontal Sync   5 Vertical Sync   4 Ground   3 Blue Signal   2 Green Signal   1 Red Signal Bottom

Composite Sync Inversion Circuit

2. Modify the CPU board to output negative Csync. This is easily achieved by removing link W1 from the CPU board. W1 is not so much of a link though as the schematics might suggest but a track on the PCB. There are holes on the PCB each side of the track though so you can easily reverse the modification by fitting a wire link or zero ohm resistor to bridge the gap. The two photos below show where you need to cut on later series Defender boards and Stargate and later games boards:

Later Series Defenders Click to Enlarge

Stargate and Later Games Click to Enlarge

Since we now have the means to make JAMMA friendly Csync on our CPU, all we need to do is wire the connector up as shown in the diagrams below:

1J3

A typical CPU Board for other games (layout may vary slightly depending on revision) Click to Enlarge

CPU Board Video Connector 1J3 Stargate and Later Games Pin Connection Notes 7 Composite Sync Top 6 Horizontal Sync   5 Vertical Sync   4 Ground   3 Blue Signal   2 Green Signal   1 Red Signal Bottom

The coin-door controls consist of the inputs from the coin mechanisms and the three switches (Auto/Manual, Advance and High Score Reset) which are used to control the pricing, difficulty and bookkeeping of the game. The Advance and High Score Reset switches should be momentary and normally open; whereas the Auto/Manual switch is latching. Each switch should be wired to ground on one side and the input to the ROM boards coin door connector 2J3, which is a 10 pin Molex connector. The connection is the same for all board variants. See the diagrams below for exact wiring details:

2J3		2J3		ROM Board Coin Door Connector 2J3 All Board Types Pin Connection Notes 10 Ground Right 9 Key   8 No Connection   7 No Connection   6 Center Coin   5 Left Coin   4 High Score Reset   3 Right Coin   2 Advance   1 Auto/Manual Left
Robotron/Joust ROM Board (layout may vary with game) Click to Enlarge		Sinistar ROM Board Click to Enlarge

The player controls consist of the inputs from the control panel; each switch should be normally open and wired to ground on one side and the input to the interface board on the other. There are four types of interface board which are used in various games so the exact wiring for each will be dealt with separately below:

Note: All the pinouts shown here assume that you are wiring up an upright game.

Early Series Defender Interface Boards

		3J2 3J3		Early Series Defender Interface Board Controls Connector 3J2 Pin Connection Notes 10 Ground Top 9 No Connection   8 No Connection   7 No Connection   6 Key   5 No Connection   4 No Connection   3 No Connection   2 No Connection   1 Up Bottom		Early Series Defender Interface Board Controls Connector 3J3 Pin Connection Notes 10 Ground Top 9 Key   8 Down   7 Reverse   6 1 Player Start   5 2 Player Start   4 Hyperspace   3 Smart Bomb   2 Thrust   1 Fire Bottom
Early Series Defender Interface Board Click to Enlarge

Later Series Defender Interface Boards

		3J2 3J3		Later Series Defender Interface Board Controls Connector 3J2 Pin Connection Notes 10 Ground Top 9 P2 Up Cocktail Games Only 8 P2 Down Cocktail Games Only 7 P2 Reverse Cocktail Games Only 6 Key   5 P2 Hyperspace Cocktail Games Only 4 P2 Smart Bomb Cocktail Games Only 3 P2 Thrust Cocktail Games Only 2 P2 Fire Cocktail Games Only 1 P1 Up Bottom		Later Series Defender Interface Board Controls Connector 3J3 Pin Connection Notes 10 Ground Top 9 Key   8 P1 Down   7 P1 Reverse   6 1 Player Start   5 2 Player Start   4 P1 Hyperspace   3 P1 Smart Bomb   2 P1 Thrust   1 P1 Fire Bottom
Later Series Defender Interface Board Click to Enlarge

Stargate Interface Boards

		3J2 3J3		Stargate Interface Board Controls Connector 3J2 Pin Connection Notes 1 Up Top 2 No Connection   3 No Connection   4 No Connection   5 No Connection   6 No Connection   7 No Connection   8 No Connection   9 No Connection   10 Ground Bottom		Stargate Interface Board Controls Connector 3J3 Pin Connection Notes 1 Fire Top 2 Thrust   3 Smart Bomb   4 Hyperspace   5 2 Player Start   6 1 Player Start   7 Reverse   8 Down   9 Inviso   10 Ground Bottom
Stargate Interface Board Click to Enlarge

Robotron Interface Boards

		3J2 3J3		Robotron Interface Board Controls Connector 3J2 (Remove Jumper W1 to Enable P2 Cocktail Controls) Pin Connection Notes 1 Fire Left Top 2 P2 Move Up Cocktail Games Only 3 P2 Move Down Cocktail Games Only 4 P2 Move Left Cocktail Games Only 5 P2 Move Right Cocktail Games Only 6 P2 Fire Right Cocktail Games Only 7 P2 Fire Up Cocktail Games Only 8 P2 Fire Down Cocktail Games Only 9 P2 Fire Left Cocktail Games Only 10 Ground Bottom		Robotron Interface Board Controls Connector 3J3 Pin Connection Notes 1 Move Up Top 2 Move Down   3 Move Left   4 Move Right   5 1 Player Start   6 2 Player Start   7 Fire Up   8 Fire Down   9 Fire Right   10 Ground Bottom
Robotron Interface Board Click to Enlarge

Joust Interface Boards

		3J2 3J3		Joust Interface Board Controls Connector 3J2 Pin Connection Notes 1 No Connection Top 2 Player 2 Move Left   3 Player 2 Move Right   4 Player 2 Flap   5 No Connection   6 No Connection   7 No Connection   8 No Connection   9 No Connection   10 Ground Bottom		Joust Interface Board Controls Connector 3J3 Pin Connection Notes 1 Player 1 Move Left Top 2 Player 1 Move Right   3 Player 1 Flap   4 No Connection   5 1 Player Start   6 2 Player Start   7 No Connection   8 No Connection   9 No Connection   10 Ground Bottom
Joust Interface Board Click to Enlarge

Bubbles Interface Boards

		3J2 3J3		Bubbles Interface Board Controls Connector 3J2 NOT USED		Bubbles Interface Board Controls Connector 3J3 Pin Connection Notes 1 Move Up Top 2 Move Down   3 Move Left   4 Move Right   5 1 Player Start   6 2 Player Start   7 No Connection   8 No Connection   9 No Connection   10 Ground Bottom
Bubbles Interface Board Click to Enlarge

Sinistar Interface Boards

You may find the using a standard 8-way joystick with Sinistar page useful

		3J2 3J3		Sinistar Interface Board Controls Connector 3J2 Pin Connection Notes 1 Up/Down Switch A Top 2 Up/Down Switch B   3 Up/Down Switch C   4 Up/Down Direction   5 Left/Right Switch A   6 No Connection   7 Left/Right Switch B   8 Left/Right Switch C   9 Left/Right Direction   10 Fire   11 Sinibomb   12 No Connection   13 1 Player Start   14 2 Player Start   15 Ground Bottom		Sinistar Interface Board Controls Connector 3J3 NOT USED
Sinistar Interface Board Click to Enlarge

The power supply for the sound board has already been dealt with, next we need to wire up the speaker, volume control and the control inputs from the ROM board. All quite straightforward here, but make sure you use a 50Kohm Logarithmic 1Watt Potentiometer here. If you are wiring up a Sinistar then you'll also have to connect the Speech board to the Sound board via the 40 way ribbon cable. See the diagrams below for exact wiring details:

Click to Enlarge Sound Board		Sound Board Speaker Connector 10J2 Pin Connection Notes 1 Speaker + Left 2 No Connection   3 No Connection   4 Speaker - Right		Sound Board Volume POT Connector 10J4 Pin Connection Notes 1 Sound In (POT Centre) Left 2 Sound Out (POT Left)   3 Key   4 Ground (POT Right) Right
10J210J410J3

The cable between the ROM board and the Sound board carries the binary signals that trigger each individual sound. Simply wire each of the 7 wires pin to pin between the boards as shown below:

2J4		ROM Board Sound Interface Out 2J4 Pin Connection Notes 1 Key Left 2 Sound Bit 1   3 Sound Bit 2 Bottom 4 Sound Bit 3   5 Sound Bit 4   6 Sound Bit 5 Bottom 7 Sound Bit 6 Top 8 Sound Bit 7   9 No Connection Right		Sound Board Sound Interface In 10J3 Pin Connection Notes 1 Key Left 2 Sound Bit 1   3 Sound Bit 2 Bottom 4 Sound Bit 3   5 Sound Bit 4   6 Sound Bit 5 Bottom 7 Sound Bit 6 Top 8 Sound Bit 7   9 No Connection Right
Robotron/Joust ROM Board (layout may vary with game) Click to Enlarge

In order to build a complete JAMMA loom the first thing we need to do is decide how we are going to lay out the boards. In a Williams cabinet the boards are mounted on a grounded metal plate making sure all the boards are bonded together, however if you do not have the metal plate this is not necessary since all the boards are grounded through their Molex connectors. You can either mount them on a piece of MDF, directly to the inside of the JAMMA cab or on a metal plate if you have one. The pictures below show two suggested layouts, though of course the final choice is up to you.

Suggested Board Layout Click to Enlarge

Alternative Suggested Board Layout Click to Enlarge

Once you have laid out the boards, mark out the cable routing, number of cables and length on some paper so you can cut all the wires to length.

Cable Length and Number of Wires Marked Out Click to Enlarge

Now we are ready to make our loom. The best way is to cut all the cables first and make them into a rough loom using whatever colour scheme you have chosen. I just used red for everything except the ground wires which are black, however I have used a smaller gauge wire for economy on the controls and video wiring.

The loom cut and laid out ready for connectors to be fitted Click to Enlarge

Terminate the loom's Molex connectors one by one ensuring that the wires are going to the right place as detailed previously in this document. DO NOT terminate the JAMMA fingerboard, volume pot or set up buttons at this point. Now connect the Molex connectors to the boards and take up any slack in your loom.

The Molex connector's all terminated Click to Enlarge

Take up the slack in the loom and tie the cables together. This is best done with the boards connected to the PCB's Click to Enlarge

Next we need to wire up the volume control and set-up switches. Remember that the Auto/Manual switch should be normally closed and latching, and the Advance and High Score Reset switches are normally open with non-latching switches preferred but not essential. The best method of mounting the switches is to build the three switches and volume pot into a small box, although you could add switches to your JAMMA cab and use the JAMMA loom.

The control box built and wired up Click to Enlarge

Finally we need to wire up the JAMMA connector. The best way to do this is to use an ohmmeter to identify each wire from the Molex connector to the JAMMA loom. Identify and solder the wires in place one by one, being careful not to make any wrong connections.

The JAMMA Connector Click to Enlarge

The completed loom Click to Enlarge

Getting ready to power up your JAMMA adapter for the first time

Once our JAMMA loom is complete, and you are sure there are no mistakes you are ready to power it up. IMPORTANT! Just to be sure that you have not made any mistakes, power up the loom without any boards connected and measure the voltage at EVERY pin of the Molex connectors to ensure that all voltages are correct and there is no volts present where there should be none. When connecting all the various boards and cables up don't forget to connect the ROM and Interface ribbon cables to the CPU! Once this is done you are ready to go! CONGRATULATIONS!

The Completed JAMMA loom wired up Click to Enlarge

The CPU board connectors Note that there is NO connection to the 4 pin Molex connector Click to Enlarge	The ROM board connectors Click to Enlarge
The Sound board connectors Click to Enlarge	The Interface board connectors Click to Enlarge