Diagnosing hardware issues in arcade machines is a systematic process crucial for restoration and maintenance. The most common methodologies involve a logical progression from simple checks to complex component analysis.

The first and most fundamental step is a thorough visual inspection. Technicians look for obvious signs of damage, such as blown capacitors (which often appear bulged or leaky), burnt resistors, cracked solder joints, or corroded connectors. Loose cables, especially the JAMMA harness, are a frequent culprit for intermittent problems and are checked for secure connections.

For power-related issues, using a multimeter to test the power supply is standard practice. The +5V DC line is critical for logic circuits and is measured at the PCB itself to account for voltage drop across the wiring. Deviations beyond +/- 5% can cause erratic behavior. The AC voltages for the monitor and the -5V/+12V lines for audio are also verified.

When a game fails to boot or exhibits graphical glitches, PCB (Printed Circuit Board) diagnostics are employed. This starts with checking the ROMs; ensuring they are properly seated and, if possible, verifying their integrity using a ROM reader. Reseating socketed chips can resolve issues caused by oxidation. Logic probes and oscilloscopes are used to check for clock signals and activity on critical data and address lines from the CPU.

Monitor troubleshooting is a specialized area due to high voltages. Common tests include checking for the presence of a glow from the tube's filament, adjusting the screen control on the flyback transformer to see if a raster appears, and inspecting the yoke and deflection components. For modern LCD conversions, the diagnostic shifts to verifying the input signal and the inverter board.

Finally, input and output systems are tested. Microswitches in joysticks and buttons are checked for continuity. Coin mechanisms and door interlock switches are inspected for proper operation, as these safety features can prevent the machine from powering on. By methodically applying these diagnostic methodologies, technicians can efficiently isolate and repair the vast majority of arcade hardware failures.