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Section F-1 Section F-1
LINCOLN
®
ELECTRIC
IDEALARC DC-400
Troubleshooting & Repair Section.................................................................................Section F
How to Use Troubleshooting Guide ......................................................................................F-2
PC Board Troubleshooting Procedures.................................................................................F-3
Troubleshooting Guide................................................................................................F-4 - F-14
Test Procedures
Input Contactor Test......................................................................................................F-15
Control Transformer (T2) Voltage Test...........................................................................F-18
Main Transformer (T1) Voltage Test...............................................................................F-21
Static SCR/Diode Rectifier Bridge Test ........................................................................F-26
Active SCR Test.............................................................................................................F-29
Oscilloscope Waveforms .....................................................................................................F-33
Normal Open Circuit Voltage Waveform-Constant Current Mode................................F-33
Normal Open Circuit Voltage Waveform-Constant Voltage FCAW/GMAW..................F-34
Normal Open Circuit Voltage Waveform-Constant Voltage Subarc .............................F-35
Typical Output Voltage Waveform-Constant Voltage FCAW/GMAW............................F-36
Typical Output Voltage Waveform-Constant Voltage Subarc .......................................F-37
Typical SCR Gate Voltage Waveform-Constant Voltage Subarc ..................................F-38
Abnormal Open Circuit Voltage Waveform-Constant Voltage Subarc..........................F-39
Replacement Procedures ....................................................................................................F-40
Input Contactor (CR1) Cleaning/Replacement .............................................................F-40
Fan Motor and Blade Removal and Replacement........................................................F-42
SCR/Diode Rectifier Assembly Removal and Replacement.........................................F-44
SCR Removal and Replacement ..................................................................................F-46
Mounting of Stud Type Diodes to Aluminum Heat Sinks .............................................F-52
Main Transformer Removal and Replacement..............................................................F-54
Retest After Repair ..............................................................................................................F-61
TABLE OF CONTENTS
TROUBLESHOOTING & REPAIR SECTION