Repair Cases

Repair Case Index

Repair-case index built from real troubleshooting material: symptom, measurement, abnormal value, failed part, repair action and result.

Records

UC3846 shutdown pin active: no PWM output — Repair-case format for measured pin voltage, blocked PWM, failed transistor/opto path and restored drive waveform.
SG3525 no PWM output — A repair-case track for SG3525 control boards where the chip is powered but PWM output is blocked or missing.
KA3843 auxiliary supply repair — Repair-case track for missing or unstable 24V auxiliary rails in inverter welders.
Dual-voltage board not boosting — Repair-case track for 220V/380V conversion boards that fail to boost or switch correctly.
IGBT keeps blowing — Repair-case track for repeated IGBT or MOSFET failures caused by driver, snubber or secondary-stage faults.
MIG wire feeder does not run — Wire-feed motor, trigger input, 2T/4T logic, gas valve, TL494/CD4013 and motor drive diagnosis.
TIG no high-frequency start — HF board, spark gap, high-voltage transformer, trigger chain and no-HF fault diagnosis.
Plasma no pilot arc — HF start, pilot arc board, gas pressure, torch trigger, arc-transfer feedback and enable signal tracking.
ZX7-250 H7B power tube short-circuit case — series lamp limiter and driver-chain diagnosis.
ZX7-250 IGBT short circuit repair case — lamp limiter, H7B power tube and driver-board check.

Repair cases are rewritten as structured summaries. They are not raw scans or copied manuals.