Begin with an observable symptom
Record whether the machine has no apparent power, an unstable image, unreadable game output, missing sound or a particular input that does not register. Note the cartridge and regional unit used. Do not group all of these under “dead console.” A machine producing a picture but waiting for a selection needs a different investigation from a unit with damaged power wiring.
Return to the appropriate original setup. Epoch's manufacturer-hosted instruction booklet is the starting reference for Japanese hardware. Identify the French unit separately and use its own wiring documentation. Television tuning, incompatible display standards and an unidentified adapter must be checked before changing the video circuit.
Test controls as separate inputs
The console keypad and two game controllers should be tested independently. Use software with documented controls and a visible response for each action. Check directions one at a time, then action buttons, selection keys and Pause where the game supports them. Record failure by key and controller. A cable damaged near its exit may behave differently under ordinary movement; do not repeatedly twist it to force an intermittent connection.
The SCV core author's hardware notes describe the keypad and controller behavior implemented by that project, including the meaning of Start in its input mapping. These notes are useful for a software test, but an FPGA keyboard mapping is not a replacement-controller electrical pinout. Keep user controls, emulator bindings and physical signals distinct.
| Observation | Useful check |
|---|---|
| One cartridge fails | Correct media identity, contacts and a second known cartridge. |
| One direction fails | Controller-specific input test and cable inspection. |
| Both players fail the same selection | Game instructions and console keypad behavior. |
| Image unstable on one display | Regional output support and adapter settings. |
| New fault after opening | Connector orientation, displaced leads and prior work. |
Respect gaps in service information
Public board research is less complete than for common consoles. Do not fill that gap with guessed voltages, cartridge pinouts or capacitor values. Before board work, photograph both sides, labels and connector routes. Compare actual component identifiers with a revision-specific schematic or an original research procedure. A processor datasheet describes that component; it does not prove a particular console trace reaches the pin you expect.
Remove power before disassembly or continuity inspection. Do not short a cartridge signal as a test or adapt a connector by appearance. For cracked contacts or a damaged trace, retain photographs and the measured fault so a repair can be assessed. Avoid replacing multiple unknown parts simultaneously, which makes it difficult to determine what changed the behavior.
Verify after work
Repeat the original failing sequence, then test the other controller, keypad, sound and a second cartridge. Record the exact improvement and unresolved symptoms. Keep removed parts and a repair log with the console identifier. See homebrew research for controlled diagnostic programs and setup for the baseline.