Fault index
Small Inverter Welder Fault Index
A board-layer troubleshooting index for compact ZX7-style inverter MMA welders.
Start here
Use this index when the welder is a compact inverter MMA / ZX7-style machine. Route by visible symptom first, then map the fault to bottom board, top inverter board, middle output board or control-panel layer.
Board-layer logic
Bottom board usually covers input bridge, relay/start resistor, DC bus capacitors and auxiliary power. Top board usually covers MOSFET/IGBT devices, driver transformer and switching control. Middle board usually covers main transformer, output diodes, reactor, shunt, feedback and thermal protection.
What not to replace first
Do not replace MOSFETs only because the machine has no output. No-output may come from missing drive, transformer/output diode path, shunt feedback, output cable, or protection lockout.