Circuit path · WS bottom board
WS TIG bottom-board relay, gas and HF control
This circuit path explains the start-control role of WS TIG bottom boards: hand-switch input, 24V/control power, relay supply, gas-valve relay, HF relay, power relay, fan and post-flow timing. It helps separate start-sequence faults from inverter output faults.
Bottom-board start logic
Relay and timing checks
| Node | Normal role | Fault behavior |
|---|---|---|
| Hand-switch connector | Starts gas/HF/inverter sequence. | No trigger response, no relay click or intermittent start. |
| 24V supply | Feeds relays and logic. | Relays chatter, gas valve weak, sequence stops under load. |
| Gas-valve relay | Switches solenoid power. | HF may occur without gas, or gas may stay open. |
| HF relay | Switches HF boost/discharge circuit. | No HF, weak HF, or HF stuck on. |
| Post-flow timing capacitor | Controls gas-after-flow duration in some WS boards. | Gas delay too long or too short. |
| Blocking /封波 control | Prevents inverter drive until start conditions allow output. | Gas/HF present but no main output. |
Typical repair conclusions
Gas relay clicks but no gas
Check solenoid power, connector, relay contact and valve coil before replacing the whole board.
HF relay clicks but no HF
Move downstream to boost transformer, discharge resistor, HF cable and high-voltage silicon parts.
Gas and HF work, no output
Move upstream/downstream to blocking control, upper-board drive, middle-board output and feedback path.
Control-board boundary
The bottom board owns sequence timing and relay actions, but it does not prove that the inverter output stage is healthy. Always separate start sequence from power conversion.