Fault route · Protection / no output
ZX7 / WS protection light on, no output
Use this route when a ZX7 / WS stick or TIG inverter powers up but has no welding output, weak output or a protection lamp condition. The key is to decide whether the machine is in real over-current/over-temperature protection or false shutdown caused by feedback, auxiliary supply or control-board evidence.
This page has a specific ZX7 / WS no-output role
This is the structured ZX7 / WS route for protection light on and no output. Broad fault pages should point here when the machine family matches.
Related ZX7 / WS no-output pages
ZX7 no-output content is separated by scope: broad protection symptom, generic inverter no-output, ZX7-250 specific symptom, no-OCV subtopic and the structured ZX7 / WS diagnostic route.
First split: real protection or false protection?
Real protection
Shorted output diode, failed IGBT/MOSFET, transformer fault, fan/thermal fault or DC-bus abnormality can correctly block drive.
False protection
Broken feedback line, wrong thermal-switch state, missing 24V rail or optocoupler/control-loop fault can pull shutdown even when the power stage is not shorted.
Evidence order
Symptom table
| Observation | Likely area | Next check |
|---|---|---|
| Protection lamp on immediately | Power-stage short, thermal input, feedback/shutdown line | Check IGBT/MOSFET and output diode first, then thermal and feedback connector. |
| Fan/display normal, no output, no protection lamp | Drive enable, PWM controller, driver board or gate-drive transformer | Check drive connector and control-board output toward driver board. |
| Weak output only | Feedback error, current pot, maximum-current trim, output diode damage | Check current-control voltage and feedback return under load. |
| Trips under load | Real over-current, bad output rectifier, gate-drive imbalance, feedback loop issue | Compare no-load and loaded behavior; inspect snubber/gate-drive components. |
| Intermittent after warm-up | Thermal switch, fan, cracked solder, auxiliary supply sag | Heat/cool test thermal path and measure rails while fault appears. |
Practical rule
If the machine has a hard short in the power stage, do not force-enable PWM. If the power stage checks normal, do not replace IGBTs blindly; follow thermal, feedback and control-enable evidence.