MONSTERBASH is an open-firmware DIY interface designed to replace a JAMMA arcade cabinet’s original game PCB with a PC while retaining the cabinet’s controls, arcade monitor, speakers, and coin door. Built around an Arduino Due and a custom shield PCB, it combines USB control handling, arcade-oriented video circuitry, and audio amplification in one project.
It is not a plug-and-play beginner adapter. The difficult part is not simply connecting a PC: controls, video, audio, and power each have different requirements. An original arcade CRT also needs particular attention because a normal PC video signal may use the wrong scan rate or sync format.
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What JAMMA provides
JAMMA is an arcade-cabinet wiring standard created to make game-board replacement easier. Instead of rewiring every control and monitor connection for each game, an operator could connect compatible boards through a common harness.
A typical JAMMA harness carries several separate signal groups:
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- ★The high definition GBS-8200 Video converter is a professional game converter, which support all games such as, Amusement, Play station, for Xbox, wii, etc
- ★Supports CGA/EGA/VGA/YUV Component Signal Input. Supports VGA Output (640 x 480, 800 x 600, 1024 x 768, 1360 x 768
- ★Supports image position control & image zoom control.
- ★ Supports all types of VGA monitors (CRT, LCD, PDP, Projector, etc).
- Joystick directions and action buttons
- Player-start and coin-switch inputs
- RGB video and sync
- Speaker audio
- Ground connections
- Arcade power rails
That standardization is what makes a PC conversion practical, but “JAMMA” is not a guarantee that every cabinet is wired correctly or conventionally. Bootleg cabinets, conversions, repairs, and previous modifications are common. Inspect and test the actual harness before connecting new electronics.
MONSTERBASH is useful because a PC does not natively speak the electrical language of a JAMMA cabinet. A computer outputs USB input data, modern display signals, and low-level audio. The cabinet expects switch inputs, arcade-compatible video, and an amplified speaker signal.
How MONSTERBASH works
The project’s signal paths can be understood as three separate conversions:
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Cabinet controls ──> MONSTERBASH / Arduino Due ──> USB HID ──> PC emulator
PC video output ──> MONSTERBASH video circuitry ──> JAMMA monitor
PC audio output ──> MONSTERBASH amplifier ──> cabinet speakerThe original MONSTERBASH project on Instructables contains the project files, schematics, firmware, bill of materials, and assembly information. A Hackster overview identifies the project’s main architecture: an Arduino Due mounted to a custom shield that handles the additional video and audio circuitry.
Controls
Arcade microswitches are simple switch closures. When a player moves a joystick or presses a button, the switch connects an input to ground. MONSTERBASH reads those changes through the Arduino Due and presents them to the computer as standard USB HID devices.
The supplied firmware is described as allowing the board to appear as a USB keyboard, mouse, and joystick. That means the operating system can generally receive the inputs without a proprietary arcade driver. You still need to map the controls in MAME or another emulator, and the correct mapping may differ between games.
Video
The video path is the most cabinet-dependent part of the conversion:
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Many original JAMMA cabinets use CRT monitors that expect a low horizontal scan rate, commonly around 15 kHz. A normal PC output intended for a modern monitor may use a much higher scan rate. HDMI, DisplayPort, ordinary 31-kHz VGA, and arcade RGB are therefore not interchangeable by assumption.
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- It can convert CGA,EGA,VGA,YUV Component input Signal to the HD Monitors (CRT Monitor LCD Monitor PDP Monitor) with VGA interface (VGA video signal), and automatically scan CGA , EGA ,YUV signal, VGA output signals.
- Supports CGA,EGA,VGA,YUV Component Signal Input. CGA,EGA,VGA signal auto scan (15KHz, 24KHz, 31KHz),Supports VGA Output (640 * 480, 800 * 600, 1024 *768, 1360 *768).
- True digital 24-bit A,D converter for true 16.7-million color conversion. Supports image position control and image zoom control. Screen Display (English and Chinese)
- Supports all types of VGA monitors (CRT, LCD, PDP, Projector, etc).
Before connecting anything, identify the monitor chassis and determine its expected RGB, sync, scan-rate, and grounding requirements. Possible symptoms of an incompatible signal include a blank screen, a rolling image, unstable sync, incorrect colors, or a monitor that fails to lock onto the picture.
Audio
A PC headphone or line output is not automatically a replacement for the amplified output of an arcade PCB. MONSTERBASH includes audio amplification circuitry so the cabinet speaker can be used.
The path is:
PC line or headphone output → MONSTERBASH amplifier → cabinet speaker.
If the cabinet has one mono speaker and the PC provides stereo output, follow the project’s audio schematic or use an appropriate stereo-to-mono summing circuit. Do not simply short the left and right outputs together.
Is your cabinet a suitable candidate?
Check these points before ordering parts or assembling the board.
1. Is the harness genuinely JAMMA?
Look for the JAMMA edge connector and document its orientation. Photograph every connection, trace the wires, and use a multimeter to verify continuity. Do not rely solely on cabinet labels, color codes, or an assumption that a previous owner followed the standard.
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2. Does it use an original CRT or an LCD?
An LCD conversion may avoid some CRT-specific risks, but it can still require a suitable video converter and correct mounting. An original CRT requires confirmation of scan rate and sync compatibility before the PC is connected.
3. How many buttons does the control panel have?
A conventional JAMMA layout does not necessarily provide every input needed by a six-button fighting-game panel. Additional buttons may use a separate kick harness or custom wiring. Trace those inputs independently and confirm that the firmware or an additional encoder can support them.
4. Is the cabinet power supply healthy?
Never assume that an old arcade power supply is safe, correctly adjusted, or suitable for powering modern computer hardware. Its +5 V rail may have been adjusted for a particular arcade PCB, and an unsuitable voltage can damage logic electronics.
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- IT TAKES THE THREE SIGNALS AN OLD CABINET ACTUALLY PUTS OUT: CGA, EGA and YUV component all go in, and the board scans 15kHz, 24kHz and 31kHz horizontal rates on its own rather than asking you to set them. Hit the AUTO key and it looks for the CGA or EGA signal again, which is what you do after swapping a game board.
- THE VGA SIDE GIVES YOU FOUR RESOLUTIONS AND DRIVES ANY VGA SCREEN: Output runs at 640 x 480, 800 x 600, 1024 x 768 or 1360 x 768, and the panel on the other end can be a CRT, an LCD, a PDP or a projector. That is the whole point of this VGA converter board, which is putting a modern screen where a dead arcade tube used to be.
- THREE INPUT FORMATS, AND ONE KEY TO MOVE BETWEEN THEM: RGBS and RGBHV come in on the header, and component arrives on the Y, Pb and Pr jacks, where 480i, 576i, 480p, 576p, 720p, 1080i and 1080p at 50 or 60 are all identified automatically. The SW key steps between YPbPr, RGBS and RGBHV without opening the menu.
- A 24 BIT A TO D STAGE, SO THE PICTURE IS NOT A ROUGH APPROXIMATION: The converter digitizes to true 24 bit for 16.7 million colors, and the OSD gives you image position and zoom so a picture that lands off center can be pulled back into the panel. The menu reads in English or Chinese and the MENU key switches between them.
- IT RUNS OFF ANYTHING FROM 5V TO 12V DC, WHICH IS WHAT A CABINET ALREADY HAS: The silkscreen beside the power header reads DC 5V to 12V, so the supply already inside the machine will usually do. The board itself is 11.7 by 11.5cm, the buttons along the edge are MENU, UP, DOWN with AUTO and SW, and the box holds the board and a power supply wire.
5. What speaker arrangement does it use?
Confirm whether the cabinet has one mono speaker, multiple speakers, or a separate audio amplifier. The MONSTERBASH audio path must match the cabinet’s speaker impedance and wiring.
Hardware and tools
MONSTERBASH-specific hardware
- MONSTERBASH PCB
- Arduino Due
- Components specified in the project’s bill of materials
- JAMMA edge connector or compatible cabinet connection
- USB cable
- Headers, wiring, terminals, and mounting hardware
The exact component values, pin assignments, firmware revision, PCB dimensions, power tolerances, and video timings should come from the original project files. The available editorial overview does not establish those details, so they should not be guessed from a generic JAMMA pinout.
Workshop equipment
- Temperature-controlled soldering iron
- Fine tip, solder, flux, and cutters
- Wire strippers and crimping tools
- Multimeter with continuity testing
- Magnification and strong lighting
- Heat-shrink tubing and insulated connectors
- Nonconductive mounting hardware
- Basic ESD precautions
Most of the build is described as through-hole assembly, but the project also includes at least one SMD chip. That makes magnification, flux, careful inspection, and the ability to identify solder bridges important.
Recommended build sequence
1. Document the cabinet first
- Photograph the existing JAMMA harness from several angles.
- Identify the monitor type and chassis.
- Record the cabinet power-supply outputs.
- Check for extra button, service, test, or kick-harness wiring.
- Confirm the edge-connector orientation and trace important lines with a multimeter.
2. Source the project files and parts
Use the original MONSTERBASH documentation for the schematic, bill of materials, PCB files, and firmware procedure. The Hackster article reports that the board can be fabricated through PCB manufacturing services, including PCBWay, but fabrication availability and cost depend on the current board files, order quantity, finish, shipping destination, and date. A fabrication service such as PCBWay produces the board; it does not automatically supply a tested, assembled, working adapter.
3. Assemble and inspect the PCB
Populate parts in an order that keeps access clear, normally starting with low-profile passive components and proceeding to larger through-hole parts. Observe the orientation of polarized capacitors, diodes, integrated circuits, connectors, and the Arduino headers.
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4. Install and program the Arduino Due
Mount the Arduino Due so that its USB connector remains accessible and the board cannot contact the cabinet chassis or other conductive hardware. Load the project firmware using the process documented by the original project. Do not substitute commands, pin numbers, or firmware files from an unrelated Arduino project.
Before connecting the cabinet, connect the Due to a computer with a known-good USB cable and verify that it enumerates as the expected USB input devices. If it is not recognized, troubleshoot the board and firmware independently rather than adding cabinet wiring to the fault.
5. Bench-test the controls
Test each joystick direction, action button, player-start switch, and coin switch individually. Confirm that every input changes state once, returns correctly, and is not stuck or duplicated.
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For a six-button panel, trace the extra harness separately. Standard JAMMA wiring may not include all of those inputs, so the additional controls may require available MONSTERBASH inputs or a separate encoder.
6. Test video separately
Establish the monitor’s expected scan rate and sync format before making the connection. If possible, test the computer and conversion circuitry with the cabinet monitor disconnected or with a known-compatible test display. A normal PC video output should not be connected directly to an original arcade CRT unless its signal format is explicitly compatible.
7. Test audio at low volume
Begin with the PC volume low. Confirm the amplifier’s power and input wiring, then connect the speaker path specified by the project. Listen for hum, clipping, and distortion, and check for unusual heat from the amplifier or power components.
8. Make the cabinet connection
With power removed, check for shorts between power, ground, video, audio, and control lines. Verify polarity and connector orientation. Power the cabinet with the interior accessible so you can immediately disconnect it if you see smoke, hear abnormal buzzing, smell overheated insulation, or observe an unstable display.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errors9. Configure the emulator
Map controls globally first, then add per-game overrides only where necessary. Configure coin, start, pause, service, test, exit, and front-end navigation functions. A hidden service button or deliberate shifted command is preferable to an easily triggered exit shortcut.
Once the configuration works, back it up. A cabinet that has no keyboard or mouse is much easier to recover when a known-good emulator configuration is stored separately.
10. Run a controlled burn-in
Test several games, both players, coin insertion, all buttons, and front-end navigation. Watch for video flicker, intermittent inputs, amplifier distortion, unusual heat, and power-supply noise. Stop if the cabinet develops a smell, buzzing, unstable picture, or repeated resets.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Power and CRT safety
Arcade cabinets contain hazardous mains wiring and, in CRT models, potentially dangerous stored voltages. Disconnect mains power before working inside the cabinet. Do not work around a CRT chassis unless you understand the relevant safety procedures; switching off the cabinet does not necessarily make every part of the monitor safe to touch.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchKeep the PC’s power system conceptually separate from the arcade power rails unless the MONSTERBASH documentation explicitly specifies the arrangement. Measure cabinet voltages under load, isolate any added DC branch where practical, and preserve protective earth, fusing, strain relief, and cabinet safety features.
The most important video warning is simple: do not treat an arcade CRT as an ordinary VGA monitor. Confirm the scan rate, sync type, polarity, RGB levels, and grounds before connection. If the monitor requirement is unclear, stop and obtain the chassis documentation or professional help.
Common problems and recovery steps
| Symptom | Likely causes | First action |
|---|---|---|
| No USB device | Firmware, cable, power, or damaged USB interface | Test the Arduino Due by itself with a known-good cable and reload the documented firmware |
| Stuck joystick direction | Wrong microswitch terminal, shorted wire, solder bridge, or mapping error | Check the common and normally open terminals, then test continuity with power removed |
| No image | Wrong scan rate, sync format, wiring, or monitor fault | Verify the monitor requirements and disconnect the signal until compatibility is established |
| Wrong colors | RGB order, missing ground, or incorrect signal connection | Check the project’s video wiring against the cabinet’s actual harness |
| Quiet speaker | Missing amplifier path or incorrect audio connection | Confirm that the speaker is connected to the amplifier output, not directly to the PC |
| Hum or distortion | Grounding, excessive input level, poor mono summing, or speaker mismatch | Lower the source volume and verify the audio schematic, grounding, and speaker requirements |
| Missing buttons | Kick harness, unsupported input, or emulator mapping | Trace auxiliary wiring and check the firmware and emulator mappings separately |
| Cabinet resets or overheats | Unstable supply, incorrect voltage, overload, or wiring fault | Switch off immediately and measure the power rails before further testing |
A common control-wiring error is using the wrong microswitch contact. The input should normally use the switch’s common and normally open terminals; using the normally closed contact can produce stuck or erratic behavior. Ultimarc’s I-PAC2 documentation describes the same practical issue for arcade control wiring.
MONSTERBASH versus buying an adapter
| Criterion | MONSTERBASH | Commercial interface |
|---|---|---|
| Purpose | Controls, video, and audio in one open DIY project | Depends on the specific product |
| Cost | PCB, components, tools, shipping, and build time | Higher upfront purchase cost but less assembly |
| Skill level | Advanced soldering, wiring, firmware, and video troubleshooting | Usually beginner to intermediate, depending on the monitor |
| Repairability | High if the schematics and firmware remain available | Depends on manufacturer documentation and support |
| Flexibility | High and customizable | Limited to the product’s inputs and signal support |
| Availability | PCB and components must be sourced separately | Depends on current stock and model |
| Reversibility | Can be installed as a removable adapter | Typically also reversible |
Controls-only option: Ultimarc I-PAC2
If the cabinet’s video and audio are already solved, a commercial control encoder may be the simpler choice. Ultimarc lists the I-PAC2 with 32 programmable inputs, keyboard, gamepad, and XInput modes, ground-referenced switch inputs, programmable mappings, and shift functions. The product page displayed a price of $39.00 when viewed on August 18, 2026; prices and availability can change.
An I-PAC2 is not a direct equivalent to MONSTERBASH. It does not by itself provide arcade-CRT video conversion, audio amplification, a JAMMA edge-connector breakout, cabinet power integration, or CRT safety protection. It is appropriate when you need controls only.
Dedicated JAMMA interfaces
Ultimarc’s product navigation lists J-PAC as a separate JAMMA interface category, making it a more relevant commercial comparison than a generic USB encoder. Before purchase, verify the current product page for availability, button support, video requirements, monitor compatibility, and whether separate video-conversion hardware is needed. Those specifications should not be inferred from the I-PAC2 page.
Who should build MONSTERBASH?
MONSTERBASH is a strong fit if you want an open, repairable, customizable project; are comfortable assembling a PCB; want to preserve an original cabinet experience; and are prepared to verify JAMMA wiring and CRT requirements yourself.
It is a poor fit if you want plug-and-play installation, have no experience around CRT or mains hardware, cannot document a modified cabinet, or only need USB controls for a modern display. In those cases, a controls encoder or a current dedicated JAMMA interface may reduce risk and troubleshooting time.
Availability is another consideration. The sources establish MONSTERBASH as a DIY project, but they do not establish that finished boards, component kits, or ongoing firmware support are currently guaranteed. Confirm that the original files and required parts are obtainable before committing to the build.
Bottom line
MONSTERBASH is best understood as a complete DIY conversion architecture rather than a simple USB encoder. It translates cabinet controls to USB HID, provides an arcade-oriented video path, and amplifies PC audio for the cabinet speaker, all while aiming to minimize permanent cabinet modification.
That combination is valuable, but it also creates three separate engineering tasks. Verify the harness, identify the monitor, isolate and measure the power systems, and test each signal path independently. If you want the project itself, use the original Instructables files. If you want the lowest-risk controls conversion, choose a controls encoder such as the I-PAC2—but do not expect it to solve the cabinet’s video and audio requirements.
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