Faults
Fault Diagnosis Index
Fault-first troubleshooting index for no-output, no-24V auxiliary power, no-PWM, wrong voltage, MIG, TIG and plasma faults.
Records
- Inverter welder powers on but no output — A symptom-first guide for welders where the fan or display works but welding output is missing.
- Auxiliary power supply no 24V — KA3843 / KA3845 startup, output feedback, PC817, zener, current-sense and load-pulling faults.
- Control board shutdown / no PWM — Tracks powered control boards with blocked PWM output due to shutdown, feedback or protection paths.
- Protection light on — Overcurrent, thermal and feedback diagnosis for welders entering protection mode.
- Welder connected to 380V by mistake — Wrong-voltage damage path: input fuse, varistor, rectifier, capacitors and auxiliary power.
- Dual-voltage welder not boosting — 220V/380V detection, LM358 comparators, relays, optocouplers and DC bus voltage errors.
- MIG wire feed not working — Mechanical and control-board diagnosis for MIG wire-feed motor, trigger and 2T/4T logic.
- TIG no high frequency — HF board, spark gap, high-voltage transformer, trigger chain and no-HF diagnosis.
- Plasma cutter no pilot arc — HF start, pilot arc board, gas pressure, torch trigger and arc-transfer feedback diagnosis.
- SG3525 no PWM output — SG3525 powered but no waveform or blocked output in welder control modules.
- UC3846 no output — UC3846 no-output, shutdown and feedback diagnosis for inverter welders.
- IGBT / MOSFET keeps blowing — Repeated power-stage failure diagnosis: driver waveform, snubber, transformer and secondary rectifier.
- Input short diagnosis with series lamp limiter — lamp-limiter method for hard shorts and power-stage faults.
- ZX7-250 IGBT short circuit — lamp limiter, H7B/power tube, control rails and driver-board checks.
- ZX7-250 blows fuse or lights lamp limiter — short-circuit triage before replacing parts.
- ZX7-250 IGBT keeps blowing — repeated device failure and gate-drive diagnosis.
- ZX7-250 fan runs but no welding output — 510V DC bus check and control-path branching.
- ZX7-250 no 510V DC bus — Power board, bridge rectifier, capacitor and relay checks.
- ZX7-250 trips breaker on power-on — Input-side hard short and silicon bridge diagnosis.
- ZX7-250 fault light on no output — Protection, upper board and secondary rectifier checks.
How to use this section
Fault pages begin with user symptoms, then guide users toward board-level causes.