Lincoln Electric SVM141-A User Manual

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Section F-1

Section F-1

SQUARE WAVE TIG 275

TABLE OF CONTENTS

- TROUBLESHOOTING & REPAIR SECTION -

Troubleshooting & Repair Section......................................................................................Section F

How to Use Troubleshooting Guide ............................................................................................F-2

PC Board Troubleshooting Procedures.......................................................................................F-3

Troubleshooting Guide ................................................................................................................F-4

Test Procedures

High Frequency Circuit Disable Procedure ........................................................................F-18

T1 Main Transformer Test...................................................................................................F-20

Gas (Water) Solenoid Test..................................................................................................F-24

Static SCR Test...................................................................................................................F-26

Active SCR Test ..................................................................................................................F-29

Oscilloscope Waveforms

Normal Open Circuit Voltage Waveform—AC TIG Mode ...................................................F-33

Normal Open Circuit Voltage Waveform—DC TIG Mode ...................................................F-34

Normal Open Circuit Voltage Waveform—AC Stick Mode .................................................F-35

Normal Open Circuit Voltage Waveform—DC Stick Mode .................................................F-36

Typical Output Voltage Waveform—Machine Loaded—AC TIG Mode ..............................F-37

Typical Output Voltage Waveform—Machine Loaded—DC TIG Mode ..............................F-38

Typical Output Voltage Waveform—Machine Loaded—AC Stick Mode.............................F-39

Typical Output Voltage Waveform—Machine Loaded—DC Stick Mode ............................F-40

Abnormal Open Circuit Voltage—DC TIG Mode—One Output SCR Not Functioning .......F-41

Replacement Procedures

High Voltage Transformer Removal and Replacement ......................................................F-42

SCR Bridge Assembly Removal and Replacement............................................................F-45

Polarity Switch Removal and Replacement........................................................................F-49

Main Transformer and Output Choke Assembly Removal and Replacement ....................F-54

Retest After Repair ....................................................................................................................F-59