Home / Diagnostics / Component testing

Bench evidence

Welding Machine Component Testing Guide

Do not diagnose an inverter welder from the front panel alone. This page extracts the usable bench-test figures from the source pages and converts them into English-labeled repair evidence.

Use cropped figures, not full-page scans

The useful repair data is the meter hookup, terminal map and expected reading. Full textbook pages have been removed from this version.

Cropped diode meter hookup: forward conduction should be low; reverse blocking should be open or very high.
Cropped diode meter hookup: forward conduction should be low; reverse blocking should be open or very high.
Cropped dual-diode module detail: the 20040 marking is treated as a 200A / 400V class module reference.
Cropped dual-diode module detail: the 20040 marking is treated as a 200A / 400V class module reference.
Cropped three-phase bridge reference: test each internal diode path between AC input and DC output terminals.
Cropped three-phase bridge reference: test each internal diode path between AC input and DC output terminals.

Quick decision table

PartNormal evidenceReject evidence
Single diodeConducts one direction, blocks reverse direction.Zero both ways or open both ways.
Dual diode moduleEach diode path behaves like a diode.One path shorted or fully open; replace module.
Three-phase bridgeAll six internal diode paths are consistent.Any shorted/open path or burned terminal.
IGBT moduleGate charge changes C-E behavior; built-in diode remains directional.Permanent C-E short, no response, or asymmetric branches.
Cropped IGBT terminal map: identify G, E and C before any meter test.
Cropped IGBT terminal map: identify G, E and C before any meter test.
Cropped driver-branch circuit: compare all gate-drive branches before installing a replacement IGBT.
Cropped driver-branch circuit: compare all gate-drive branches before installing a replacement IGBT.