TIG start routing

ZX7-III TIG Start Sequence and HF Fault Routing

Use this page when stick welding works but TIG start, gas, HF or downslope behavior does not.

Why TIG faults should not be mixed with MMA output faults

A ZX7-III can weld in MMA mode while the TIG start path still fails. Treat torch switch, gas control, HF/scratch-start logic, isolation transformer and output power as separate evidence layers.

Redrawn TIG start sequence: MMA/TIG mode change, torch switch action, OCV state, HF/scratch start and gas/downslope functions.

TIG symptom table

Symptom	Likely evidence layer	First checks
MMA works, TIG does not	TIG control path	Torch switch line, isolation transformer, control board, TIG mode switch wiring.
HF spark exists but arc will not transfer	HF path vs output path	Torch lead, work return, polarity, output OCV and HF coupling path.
No gas	Gas-control path	Solenoid wiring, gas valve, control board command and AC auxiliary supply.
Gas flows continuously	Valve or control stuck	Debris in solenoid, stuck valve, control board output held on, mode-state issue.
No OCV	Output rectifier / control supply	20040 module, control board, A/V switch, display circuit and transformer/auxiliary supply.

Diagnostic path

Symptom → TIG no start. Evidence → MMA output, OCV, torch switch, gas valve, HF spark. Next page → ZX7-III model reference.