Upgrading your arcade with a new jamma harness helps it work better and last longer. A jamma harness links your game board to the controls, power, and screen in your cabinet. You get more games to work and fixing problems is easier with a good harness. Many people think this upgrade is easy if you follow simple steps. You can feel sure as you make your arcade better.
Key Takeaways
Getting a JAMMA harness makes your arcade work better and lets you switch games more easily.
Make sure your arcade cabinet works with JAMMA before you buy a harness so you do not have problems.
Pick a good harness that has easy-to-read wiring diagrams and safety labels for a safe setup.
Install the harness by following clear steps, like hooking up power, video, and controls the right way to stop errors.
Check your setup carefully after you finish to find problems early and make sure it all works right.
What Is a JAMMA Harness?
JAMMA Standard Overview
You might ask why many arcade cabinets have the same wiring. This is because of the jamma standard. In the 1980s, arcade makers had a big problem. Every game used different wires, so changing games was tough. The Japan Amusement Machine and Marketing Association made the jamma standard in 1985. This standard gave rules for wiring arcade cabinets and game boards.
The jamma standard has a 56-pin edge connector.
It puts power, video, audio, and controls in one spot.
You can move game boards between cabinets that use the jamma standard.
The jamma standard fixed the problem of different wiring.
Now, arcade owners could switch games fast. They did not have to redo all the wires. The jamma standard made fixing and changing games much easier.
Harness Features & Compatibility
A jamma harness links your arcade game board to the controls, power, monitor, and speakers. The harness uses the jamma standard, so it works with lots of games. It gives you an easy way to connect everything inside your cabinet.
Some main features of a jamma harness are:
Wires with colors to help you set it up
Connectors already on buttons and joysticks
It carries video and audio signals
It is long enough for most cabinets
You need to check if your arcade cabinet uses the jamma standard before you buy a harness. Most old cabinets do, but some new or custom ones might need adapters. When you use a jamma harness, your arcade can play more games. You do not have to change the wires every time you try a new game.
Tip: Always make sure the pinout on your game board matches the jamma harness. This stops wiring mistakes and keeps your arcade safe.
Choosing the Right JAMMA Harness
Quality & Materials
When you choose a jamma harness, look at the wire quality. Good harnesses use UL1007 wire. This wire bends without breaking and fits inside your arcade cabinet. It also follows safety rules. UL1007 wire comes in different sizes. The most common are 18AWG and 22AWG. The table below gives more details:
Wire Type | Gauge | Compliance | Description |
UL1007 | 18AWG | UL Standards | Flexible, good for low current, fits most jamma harnesses. |
UL1007 | 22AWG | UL Standards | Smaller, easy to bend, helps with tight spaces in cabinets. |
UL1007 | 22AWG | RoHS Compliant | Soft insulation, saves space, safe for arcade use. |
A strong harness will last longer and keep your arcade safe.
Key Features to Consider
You should look for features that make your jamma harness simple to use. These features also help your arcade work with new games. Check for these important things:
The harness should match the jamma standard pinout and have a 28-pin connector.
It should support joysticks, buttons, and trackballs.
Extra button support and kick harness options are good for custom setups.
Wires for -5v are needed if your game board uses them.
VGA or HDMI output and an audio jack make connections easy.
Safety marks like CE or FCC show it is tested.
Clear wiring diagrams and setup guides help you install it.
Tip: Pick a harness with a good guide. This helps you set it up without mistakes.
Where to Buy
You can buy jamma harnesses from many online stores. Some trusted sellers give good customer service and fast shipping. Here is a list of popular places to buy:
A good jamma harness costs between $20 and $50. Always check for a return policy and technical support. This makes your arcade upgrade much easier.
Installation Steps
Tools & Preparation
Before you start, gather all the tools you need. This helps you work faster and avoid mistakes. You will need:
Screwdriver for connecting the power supply to the JAMMA harness
Wire cutters and strippers for trimming wires
Quality ratcheting crimper for making strong connections
Electrical tape or heat shrink tubing for safety
Multimeter for checking connections
Lay out your JAMMA harness and check that you have all the connectors. Make sure your arcade cabinet is unplugged before you begin. Organize your workspace so you can find each tool quickly.
Tip: Use a good crimper instead of a cheap one. This gives you better and more reliable connections.
Power Connections
You must connect the power supply to the JAMMA harness. Find the power wires on the harness. These usually have clear labels. Use your screwdriver to attach the wires to the power supply terminals. Make sure you match the colors and labels.
Avoid using cheap crimpers. They can cause weak connections. A quality ratcheting crimper makes the job easier and safer. Check each connection by gently tugging on the wire. If it comes loose, redo the crimp.
Double-check the orientation of the connector before plugging it into the board. The JAMMA connector only fits one way. If you force it, you can damage the pins.
Video Wiring
The JAMMA harness has special wires for video signals. These wires connect to the monitor chassis. Look for the red, green, blue, sync, and ground wires. The JAMMA standard uses pins 12-14 and N-P for these signals.
Connect each color wire to the matching spot on your monitor. The video signal wires must go to the chassis that creates the signals for the yoke. Do not mix up the video wires and yoke wires. They serve different jobs.
If you want better picture quality, you can use an RGB mod. This works well if your monitor or TV has component inputs.
Note: You can improve video quality by separating the video wires from the rest of the harness. Pull the video wires away from the bundle to reduce interference.
Controls Setup
You need to connect the controls to the JAMMA harness. Each button and joystick has its own wire. The harness usually comes with connectors for easy setup.
Tie all ground wires together. This keeps the controls working right. Each player should have a ground loop. The coin door and switcher also need their own ground loops. Connect unused ground wires to a common ground point. This keeps everything safe and working.
Do not rely only on the PCB for ground. Some boards do not connect all ground traces. Make sure every ground point in the cabinet is linked.
Audio & Coin Wiring
Follow these steps to wire the audio and coin mechanisms:
Get your JAMMA harness ready. It has a standard edge connector with two rows of 28 pins.
Learn the wiring code for the JAMMA harness. This includes audio and coin connections.
Plug the harness into the JAMMA board. Make sure the connector is facing the right way.
Group the wires for easy setup. Keep player controls and power wires together.
Use the board’s test mode to check your work. Make sure the audio and coin features work.
Be careful with the coin door lights. The 12V on the JAMMA harness is for the game board, not the coin doors. If you use 12V for coin lights, they may flicker or dim. Most classic cabinets use AC 6V for coin lights. Check your cabinet’s wiring before you connect the lights.
Handling Extra Wires
You may find extra wires on your JAMMA harness. These can be for extra buttons, test switches, or unused features. Do not cut them off. Instead, bundle them neatly with zip ties or tape.
Label each extra wire if you can. This helps you later if you add new features. Keep the extra wires away from power and video wires to avoid noise or interference.
Tip: Save all unused connectors and wires. You might need them for future upgrades or repairs.
Testing & Fixes
Power-On Test
You finished installing your jamma harness. Now you need to check if everything works. Start by building a simple jamma test bench. Use a display that matches the jamma standard, like a 15kHz CRT monitor or a VGA converter. Connect a power supply that gives +5V, +12V, and -5V. Set up the controls with a test mode switch, coin button, joystick, and fire buttons. Add a speaker for audio output from the jamma board.
Follow these steps for your first power-on test:
Plug the jamma connector into the board. Make sure the connector fits the right way.
Turn on the power supply. Watch for lights or sounds from the arcade board.
Check the display. You should see the game screen or test mode.
Press each button and move the joystick. Listen for sounds and watch for movement on the screen.
Use a digital multimeter to check voltages. Make sure the board gets the right power.
If you have a logic probe, test the signal lines for activity.
Tip: Always keep your hands away from live wires when you power on the system.
Troubleshooting Tips
Sometimes things do not work after you install a jamma harness. You can fix most problems with simple checks.
Controls Not Working
Connect only one joystick and one button to a controller. Leave LEDs disconnected.
Add each button one at a time. If controls stop working, you found a miswired button.
Fix the wiring and test again.
Video Problems
You might see a green screen or a grid of small screens. This means the video signal is unstable.
Try a separate regulated 5V power supply for the converter.
Add a 75-ohm resistor between sync and ground.
Place a 220uF capacitor in-line between the jamma and converter connections.
These steps help stabilize the video output.
Quick Reference Table
Problem | Solution |
No power | Check power supply and connector orientation |
No video | Use regulated supply, add resistor/capacitor |
Controls fail | Test buttons one by one, fix miswiring |
Note: Label all wires and connectors. This makes future fixes much easier.
You can upgrade your arcade with a new jamma harness using basic tools and careful steps. Most hobbyists finish this project without trouble. If you run into problems, try these quick fixes:
Swap a button microswitch with one that works.
Test another harness if you have one.
Connect the wire to a working button.
Replace the conversion board or connector.
Use a multimeter to check wire continuity.
Stay patient and label your wires. You can add more features or custom controls in the future.
FAQ
What is the JAMMA standard?
The JAMMA standard is a wiring rule for arcade cabinets. It lets you swap game boards easily. You connect power, video, audio, and controls with one harness.
Can I use a JAMMA harness in any arcade cabinet?
You can use a JAMMA harness in most classic cabinets. Some newer or custom cabinets may need adapters. Always check your cabinet’s wiring before you start.
How do I know if my game board needs -5V?
Check your game board’s manual or label. If it lists -5V, your harness must have a -5V wire. Many modern boards do not need it, but some older ones do.
What tools do I need to install a JAMMA harness?
You need a screwdriver, wire cutters, a crimper, electrical tape, and a multimeter. These tools help you connect wires safely and check your work.
Why does my video look wrong after installing the harness?
You may have mixed up the video wires or need a resistor on the sync line. Double-check your connections. Try adding a 75-ohm resistor between sync and ground for a stable picture.
