Lincoln Electric PRECISION TIG 185 SVM169-A Service Manual page 39

Section F-1
- TROUBLESHOOTING & REPAIR SECTION -
Troubleshooting & Repair Section ........................................................................Section F
How to Use Troubleshooting Guide..............................................................................F-2
PC Board Troubleshooting Procedures and Replacement...........................................F-3
Troubleshooting Guide ..................................................................................................F-4
Test Procedures
High Frequency Circuit Disable Procedure ..........................................................F-15
T1 Transformer Test ..............................................................................................F-17
Static SCR Test ....................................................................................................F-21
Active SCR Test....................................................................................................F-25
Oscilloscope Waveforms
Normal Open Circuit Voltage Waveform-AC TIG Mode .......................................F-29
Normal Open Circuit Voltage Waveform-DC TIG Mode.......................................F-30
Normal Open Circuit Voltage Waveform-AC Stick Mode.....................................F-31
Normal Open Circuit Voltage Waveform-DC Stick Mode ....................................F-32
Typical Output Voltage Waveform-Machine Loaded AC TIG Mode.....................F-33
Typical Output Voltage Waveform-Machine Loaded DC TIG Mode ....................F-34
Typical Output Voltage Waveform-Machine Loaded AC Stick Mode ..................F-35
Typical Output Voltage Waveform-Machine Loaded DC Stick Mode ..................F-36
Abnormal Open Circuit Voltage-DC TIG Mode One SCR not Functioning..........F-37
Replacement Procedures
SCR Bridge Assembly Removal and Replacement .............................................F-39
Polarity Switch Removal and Replacement .........................................................F-45
High Voltage Transformer Removal and Replacement ........................................F-49
Main Transformer and Output Choke Removal and Replacement ......................F-53
Retest after Repair ......................................................................................................F-57
TABLE OF CONTENTS
PRECISION TIG 185
Section F-1