Fault route · WS TIG start sequence
WS TIG no gas, no HF or no arc routing
Use this route for WS-200P, WS-200S, WS-250 and similar TIG machines when pressing the torch switch does not produce the expected gas, high-frequency start and welding-current transfer sequence. Start from the first missing action, not from the board you suspect.
Expected TIG start sequence
Press torchHand switch reaches bottom/control board.
Gas valveSolenoid relay opens gas before or during HF start.
HF relayHigh-frequency circuit receives a short start command.
Inverter driveUpper board enables main power stage.
Arc transferMain welding current takes over after HF ignition.
Post-flowGas remains after output stops according to timing circuit.
Fault route by first missing action
| First missing action | Likely section | Checks |
|---|---|---|
| No gas, no relay click, no HF | Hand-switch input, 24V rail, bottom-board relay power | Check torch switch continuity, 24V/control supply and relay coil command. |
| Gas opens, no HF | HF relay command or HF board | Check HF relay coil, HF control connector, boost transformer, discharge resistor and high-voltage silicon parts. |
| HF present, no arc transfer | Upper-board drive or middle-board output | Check inverter drive enable, MOSFET/gate-drive, main transformer, secondary rectifier and feedback line. |
| Arc starts then stops | Feedback/protection or thermal path | Check current/voltage feedback, thermal switch, protection lamp path and auxiliary supply sag. |
| Gas keeps flowing too long | Post-flow timing section | Check post-flow switch, timing capacitor and gas relay release path. |
Do-not-replace-first list
Do not replace MOSFETs first
No gas or no HF can be entirely bottom-board/HF-command related.
Do not replace HF transformer first
Confirm relay command and HF control input before blaming the transformer.
Do not replace control board first
Feedback, thermal switch, relay supply and connector harness can create the same symptoms.
Best field method
Record the torch response in order: relay click, gas, HF sound/spark, protection lamp, output current and post-flow. That sequence usually reveals which board owns the fault before measurements become complex.