Board reference · TIG HF start
WS-250 HF arc-start board reference
Use this page when a WS-250 / WS-series TIG welder has gas but no high-frequency start, weak HF, HF stuck on, or HF relay action without arc ignition. The board-level goal is to separate command, relay, transformer, discharge path and coupling faults before replacing the entire HF board.
HF board role map
The HF arc-start board sits between the torch-start command and the welding output path. It does not create the main welding current; it creates a high-voltage, high-frequency ignition path that should appear only during the TIG start interval.
Connector and component reference
| Area | What it does | Fault symptom |
|---|---|---|
| HF control input | Receives timing command from bottom/control board. | Gas works but HF relay never acts. |
| HF relay | Connects power to HF transformer/discharge circuit. | Relay clicks but no HF, or contacts stick and HF stays on. |
| Boost transformer | Creates high voltage for arc-start pulse. | Relay works but no spark, weak HF, visible winding damage or open secondary. |
| Discharge resistor | Limits and shapes discharge energy; can protect and stabilize the HF path. | Open resistor can stop or weaken HF; wrong value can stress HV components. |
| HV diode / silicon stack | Rectifies or shapes high-voltage pulse path. | Short/open HV silicon can kill HF or cause unstable ignition. |
| HF cable connector | Carries HF energy toward torch/output coupling path. | HF present on board but not reaching torch or leaking inside cabinet. |
| Gas valve connector | Some HF boards share physical routing with solenoid/start wiring. | Gas and HF faults may appear together if start harness is wrong. |
Safety warning
HF arc-start boards can generate dangerous high-voltage pulses. Do not probe the HF output with ordinary meters or exposed oscilloscope grounds. Check command and relay-side evidence first, then use qualified high-voltage test methods only when necessary.