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Start from what the machine is doing

Welder faults

Choose the visible symptom first. Each group points to the first safe checks, the relevant circuit area and the next diagnostic sequence.

Fast starting points

Open the route that best matches the evidence already available.

01

No power or no 24 V

Check the auxiliary supply, startup VCC and low-voltage rails.

Open this route →02

Powers on but no output

Separate DC-bus, control, driver and secondary-output faults.

Open this route →03

Power devices keep failing

Stop repeated replacements and verify the full drive path.

Open this route →04

Process-specific fault

Open plasma, MIG or TIG symptom routes.

Open this route →

Power and startup faults

Use these when the machine is dead, trips the supply or never establishes its control rails.

FaultAuxiliary supply has no 24 VTrace startup VCC, switching, secondary rectification and loading.FaultInput short or bright lamp limiterCheck the bridge, DC bus and power devices before full mains.Model faultZX7-250 trips the breakerSeparate bridge-rectifier and DC-bus shorts.Damage faultConnected to 380 V by mistakeInspect surge, rectifier, bulk-capacitor and auxiliary-supply damage.

Output and protection faults

Use these when fans or indicators work but welding output is missing, weak or blocked.

FaultPowers on but no welding outputFollow DC bus, PWM, driver and secondary checks.FaultProtection light remains onSeparate true overcurrent, temperature and false feedback.Fault workflowIGBT or MOSFET keeps blowingVerify gate drive, snubber, load path and startup method.Control faultControl board shutdown / no PWMCheck supply, reference, oscillator, shutdown and output stages.

MIG, TIG and plasma faults

Start with the process sequence when the main inverter appears alive.

MIG faultMIG wire feed not workingCheck trigger, board supply, motor output and speed feedback.TIG faultTIG has no high-frequency startSeparate gas, torch command, HF generation and output readiness.Plasma faultPlasma cutter has no pilot arcCheck air, HF, pilot DC and transfer feedback.Input-system faultDual-voltage board does not boostCheck relay command, bridge configuration and DC-bus rise.

Checks before another power-up

Use a controlled sequence instead of replacing parts and applying full mains immediately.

ToolIGBT replacement precheckRecord resistance, gate-path and load checks before fitting devices.ToolLamp-limiter short diagnosisInterpret lamp behavior while protecting the repaired power stage.WorkflowZX7-250 complete repair sequenceMove from power-off checks through rails, PWM and staged startup.ChecklistPreventive maintenance checklistInspect contamination, connections, cooling and electrical condition.

Next step

Need a measurement order?

Open Workflows when the symptom is confirmed but the next safe test is not clear.

WorkflowsBrowse diagnostic workflowsChoose a sequence by machine family or subsystem.Repair mapFollow a connected repair pathMove from fault to workflow, circuit, board, chip and case.CasesCompare repair casesReview measured evidence and the final fault location.