Fault route
CT-312 Mode-Specific Fault Routing
A mode-first diagnostic route for CT-312 MMA/TIG/plasma combo welders.
Quick Answer
CT-312 faults should be routed by mode first. MMA, TIG and plasma may share inverter hardware but depend on different gas, HF, torch and output evidence.
- If MMA works but TIG/plasma fails, suspect gas/HF/trigger/mode paths before the main inverter.
- If no mode has output, move toward control power, inverter switching, output rectifier and protection evidence.
- If gas/HF works but no arc transfers, move from HF/support path to main output and work-return path.
Use this page when
- CT-312 behaves differently in MMA, TIG and plasma modes.
- You need to decide whether the fault is mode-control or main power path.
- Gas, HF and output symptoms are mixed.
Do not use this page when
- The machine is a single-process ZX7 MMA unit.
- Input breaker trips before any mode can be tested.
- You need only a front-panel operation guide.
Mode-specific route table
| Observed behavior | Likely first layer | Next step |
|---|---|---|
| MMA works, TIG no HF/no gas | TIG support path: torch switch, gas, HF board. | Open bottom board / TIG gas-HF route. |
| MMA works, plasma no arc | Plasma gas/air/HF/pilot support path. | Check gas/air support and HF transfer before inverter. |
| TIG gas clicks but no OCV/no HF | PWM permission / HF command / feedback shutdown path. | Open TIG gas-click no-output/no-HF route. |
| All modes have no output | Shared inverter/output/protection layer. | Check top inverter and middle output board. |
| Protection appears in all modes | Thermal / feedback / power-device evidence. | Check middle board thermal/shunt and top board devices. |
Board references for CT-312
Move from mode symptom to board layer.