Board reference
CT-312 Bottom Board Reference
A bottom-board service reference for CT-312 MMA/TIG/plasma combo welders.
Quick Answer
The CT-312 bottom board should be treated as the control-power and relay/socket layer for a combo MMA/TIG/plasma machine, not as the whole output fault.
- Use this reference for gas, fan, HF socket, relay and auxiliary-supply symptoms.
- The bottom board can create mode-specific confusion because TIG/plasma functions depend on gas and HF support.
- Do not blame the inverter stage until bottom-board control power and relay/socket evidence are separated.
CT-312 bottom-board evidence
| Function | Board-side evidence | Related symptoms |
|---|---|---|
| Control supply | DC bus and 24 V-related auxiliary path. | Fan/gas/HF/control path dead. |
| Main relay / start resistor | Power-up control and inrush/start path. | Machine powers but does not start correctly. |
| Gas / fan / HF sockets | External load sockets tied to combo-mode support. | No gas, fan abnormal, no HF command. |
| Mode support | MMA/TIG/plasma dependence on bottom-board auxiliaries. | One mode works while another mode is missing gas/HF/arc. |
Related records
Use these after bottom-board evidence.