Real troubleshooting evidence and reusable lessons

Welder Repair Cases

Use Repair Cases when you want to see how a real fault was traced, where a wrong replacement would have happened, and what measurement evidence changed the diagnosis. A repair case should connect the symptom, board evidence, chip path, component check and reusable lesson back to the standard diagnostic workflow.

Start here by case type

Choose the repair-case pattern that matches the evidence. If you only know the general symptom, start from Faults. If you need a standard step-by-step workflow, start from Diagnostics.

Chip path

PWM shutdown and misleading IC symptoms

Cases where the PWM IC looks bad, but optocoupler, op-amp, resistor or shutdown input evidence points elsewhere.

TIG start

Gas, HF and no-current case patterns

Cases where gas or HF evidence proves one layer is alive but current permission or feedback is blocked.

Power stage

Power-device and breaker-trip lessons

Cases and routes that prevent replacing IGBTs, MOSFETs or rectifier parts before the root cause is cleared.

Model routing

Model-specific case follow-up

Use the model hub after a case pattern matches a known machine family.

How this section relates to Diagnostics

Repair Cases show what happened in a real troubleshooting sequence. Diagnostics provide the reusable workflow. A good case should end by linking the lesson back to a diagnostic route, chip page, board page, component page or tool so the user can apply the pattern on another machine.

PWM shutdown and misleading IC symptoms

Use these when the machine has control evidence but PWM output is blocked, or when replacing the PWM IC would be premature.

WS-250 Gas Click No OCV No HF CaseSG3525/CW3525 pin 4 oscillator, pins 11/14 no PWM, PC817/CA3140/R12 shutdown path. SG3525 / CW3525 PWM ControllerUse with the case to understand oscillator, output pins and shutdown behavior. Welder Chips IndexPWM, optocoupler, op-amp, driver and shutdown-path navigation. TIG Pre-Flow + HF Works, No CurrentCurrent permission, driver stage, output path and feedback shutdown route. TIG HF Present, Current Drops OutArc-transfer feedback, current feedback, protection input and PWM/current permission. WSM-315 Control BoardControl-board command layer for TIG timing, HF and current permission.

Gas, HF and no-current case patterns

Use these when the visible evidence is gas valve action, HF start, no OCV, no current, or current that drops out after start.

Gas Click But No OCV / No HF PatternGas action does not prove PWM/current permission or HF command is healthy. TIG HF Arc-Start SequenceTorch input, pre-flow gas, HF command, arc transfer and HF cutoff sequence. TIG Gas Solenoid Control PathTorch input, timing logic, output driver, solenoid coil and post-flow control. TIG Gas Flows But HF MissingUse when gas works but HF command or HF board path is missing. Pre-Flow + HF Works, No CurrentUse when start support works but main welding current is blocked. TIG HF Stuck On After Arc StartUse when arc transfer or HF cutoff evidence is abnormal.

Power-device and breaker-trip lessons

Use these when a case pattern involves shorted IGBT/MOSFET devices, breaker trip, rectifier bridge, DC bus or repeated replacement failure risk.

Power Device Failure IndexIGBT, MOSFET, rectifier bridge, output diode and repeated failure routes. IGBT / MOSFET Keeps BlowingRepeated device failure route before replacing another module. IGBT Replacement PrecheckPre-power checklist before installing replacement devices. IGBT Module TestingComponent-level IGBT testing and replacement-risk context. Rectifier Bridge / Diode Module TestingBridge rectifier and diode-mode checks. ZX7 Breaker Trip / MOSFET ShortDC bus, MOSFETs, driver transformer and output-load evidence.

Model-specific follow-up after a case pattern

After a case pattern matches the symptom, return to the known machine model or board reference to apply the lesson correctly.

WSM-315 TIG HubPanel, control board, HF arc-start, timing and current-control routes. WSE AC/DC TIG HubAC/DC, pulse, balance, secondary inverter and TIG timing routes. CT-312 Combo WelderMMA/TIG/plasma mode comparison and board-stack routing. ZX7-160/200 Small InverterBottom, top and middle board-layer routing for compact MMA welders. MIG200DL CO2 MIG WelderTrigger, gas, wire-feed, fan/display and current-control routes. TIG Welder Fault IndexGeneral TIG gas, HF, 2T/4T, post-flow, foot-pedal and current routes.