Think in systems, not just voltages
A JAMMA cabinet harness connects much more than power. It joins the game PCB to controls, RGB video, synchronization, audio and cabinet functions. The classic 56-contact JAMMA edge carries +5 V and +12 V supply positions, several ground returns and other signals. Some boards and variants additionally depend on -5 V or auxiliary connectors.
A board's power requirements must come from its exact service manual, schematic or measured, known-good setup. A connector that physically mates is not evidence of an appropriate supply.
What the labels usually indicate
| Label | Typical role | Why to verify |
|---|---|---|
| +5 V | Logic supply for many classic arcade PCBs | Incorrect voltage or drop under load can cause faults or damage |
| +12 V | Often associated with audio amplification and other loads | Not a substitute for +5 V; actual requirements vary |
| -5 V | Used by some older or nonstandard audio/analogue circuits | Not used on every board; do not assume it is needed or present |
| GND / return | Reference and current return for the board | Wrong ground connections can create unsafe or unreliable operation |
| AC mains | Input to the power supply, not a JAMMA logic rail | Shock and fire hazard; requires properly rated, protected installation |
A practical, unpowered inspection
- Identify the PCB model and find the corresponding operator or service manual.
- Trace the cabinet harness or supergun model; record modifications, adapters and edge-key orientation.
- Inspect the edge connector for contamination, damage, bridging and misalignment.
- Check power supply labeling, protective enclosure, earth bonding and cable condition without opening or modifying live equipment.
- Keep the game disconnected until a qualified person verifies the correct rails and wiring for that exact board.
Video and audio are part of electrical compatibility
Classic JAMMA RGB and sync are not automatically VGA, HDMI or television composite video. An adapter needs appropriate signal levels and a compatible display path. JAMMA speaker output may be amplified; connecting it straight to an expecting-line-level audio input can cause damage.
Also remember that multi-button games and particular platforms use auxiliary harnesses. JAMMA is a shared starting point, not a promise that every necessary wire is on the edge connector.
A good decision before the first power-on
Make a short record: board model, harness type, manual revision, required supply rails, audio mode, monitor specification and auxiliary connections. If any of those are unknown, treat the setup as unverified.
Atelier Rocky does not certify a bench supply, harness, supergun or console from a general article. Our own hardware will need separate electrical qualification before it can be offered for use.
Sources and further reading
Original documentation and specialist references consulted for this article. Always check your model and revision.
Information only: no product compatibility test is being claimed. These workshop accessories are not yet for sale.