IC-level references for repair diagnosis

Welder Chips

Use Chips when the evidence points to an IC or signal-control path: PWM controller, optocoupler, op-amp, gate-driver chain, shutdown input, feedback amplifier or control-board logic. Chip pages should help avoid the common mistake of replacing the IC before proving that power, feedback, shutdown and surrounding components are correct.

Start here by chip function

Choose the IC function that matches the evidence. If you only know the visible symptom, start from Faults. If you know the board or connector, use Boards first.

PWM

PWM controllers and shutdown pins

For SG3525/CW3525 oscillator present but no PWM output, shutdown path and gate-drive permission faults.

Feedback

Optocouplers and feedback isolation

For PC817-style feedback/shutdown paths, false protection, no output and blocked PWM evidence.

Op-amp

Op-amps and signal conditioning

For CA3140/LM324-style current feedback, protection threshold, command processing and current-control faults.

Driver

Driver ICs and gate-drive paths

For missing gate drive, repeated IGBT/MOSFET failure and inverter switching permission problems.

How this section relates to Components and Repair Cases

Chips explain IC-level behavior and pin/path logic. Components explain physical part testing. Repair Cases show real measurement sequences. For example, SG3525 pins 11/14 having no PWM does not automatically prove SG3525 is bad if shutdown, optocoupler, op-amp or bias paths are pulling it off.

PWM controllers and shutdown paths

Use these when oscillator, PWM output, shutdown input or drive permission evidence is involved.

SG3525 / CW3525 PWM ControllerPWM oscillator, output pins, shutdown behavior and surrounding-circuit diagnosis. WS-250 Gas Click No OCV No HF CaseSG3525/CW3525 pin 4 oscillator, pins 11/14 no PWM, PC817/CA3140/R12 shutdown path. 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 BoardTorch switch, panel command, gas output, HF command and current command evidence. Power Device Failure IndexGate-drive and power-device failure paths before replacing IGBTs/MOSFETs.

Optocouplers and isolation feedback paths

Use these when isolation, feedback transfer, shutdown control or false protection may be blocking PWM or output.

PC817 / Feedback Shutdown Case EvidenceOptocoupler and CA3140 path can hold PWM shutdown even when oscillator exists. LGK100L Protection LightTemperature relay, low-voltage rails and Hall feedback evidence. CT-312 Protection Common to All ModesThermal, feedback, output-stage and shared protection evidence. Hall Current Sensor DiagnosisCurrent feedback evidence for weak current, false protection and no-output faults. Connector Measurement PointsConnector evidence for feedback and current-related measurement paths. WSM/WSE Current-Control FaultsPanel command, feedback path and output-stage response split.

Op-amps and signal-conditioning paths

Use these when the fault involves current feedback, command scaling, protection threshold, shutdown comparator behavior or current-control mismatch.

CA3140 Path in WS-250 CaseOp-amp and resistor path evidence that affected SG3525/CW3525 shutdown behavior. WSM-315 Current Cannot AdjustPanel setting, control-board input, feedback path and output response. ZX7 Weak Current / Cannot AdjustCurrent potentiometer, shunt feedback, reactor and output cable evidence. MIG200DL Unstable Welding CurrentCurrent potentiometer, output cable, contact tip and board follow-up. WSE AC/DC TIG Control PanelAC/DC selector, pulse, balance and current-command logic. Component-Level DiagnosisUse component pages after IC-level evidence points to a physical part.

Driver ICs and gate-drive paths

Use these when the fault involves missing drive, repeated power-device failure, driver transformer, inverter permission or output-stage switching.

IGBT / MOSFET Keeps BlowingRepeated power-device failure route before installing another device. IGBT Replacement PrecheckPre-power checks before replacing and powering devices. CT-312 Top Inverter BoardPower devices, driver transformer, control module and top-board supply. ZX7-160/200 Board StackTop inverter board, driver transformer and middle-board output load split. ZX7 Breaker Trip / MOSFET ShortDC bus, MOSFETs, driver transformer and output-load evidence. LGK100L Burns IGBTIGBT failure and related driver/power-stage troubleshooting path.

Wire-feeder PWM controller references

TL494 / TL598 wire feeder PWM controlPWM IC checks before replacing feeder board components.

Wire-feeder PWM controller references

TL494 / TL598 wire feeder PWM controlPWM IC checks before replacing feeder board components.

Wire-feeder PWM controller references

TL494 / TL598 wire feeder PWM controlPWM IC checks before replacing feeder board components.

Chip references connected to repair routes

Chip pages should link back to the board and circuit where the chip actually affects the symptom.

TL494 / TL598 wire-feeder PWM controlPWM controller route for NBC wire-feeder motor-output and burn-back faults. NBC wire feeder boardBoard context for TL494/TL598 PWM checks. NBC PWM and burn-back circuitCircuit context for PWM, speed command and motor output.