| Lincoln Electric DC-655

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Section F-1

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–F-12
Test Procedures
Internal Trigger Circuit Test		F-13
Firing Board Test		F-17
Main Transformer (T1) Voltage Test		F-22
Control Transformer (T2) Voltage Test		F-27
Control Board Transformer (T3) Test		F-30
Input Contactor Test		F-32
Static SCR Test		F-35
Active SCR Test		F-38
Thermal Fan/Snubber Board LED Chart		F-41
Control Board LED Chart		F-42
Oscilloscope Waveforms
Normal Open Circuit Voltage Waveform-Constant Current Mode		F-43
Normal Open Circuit Voltage Waveform-Constant Voltage MIG Maximum Output		.....F-44
Normal Open Circuit Voltage Waveform-Constant Voltage MIG Minimum Output		F-45
Typical Output Voltage Waveform-Constant Voltage MIG		F-46
Typical SCR Gate Voltage Waveform-Constant Voltage MIG		F-47
Abnormal Open Circuit Voltage Waveform-Constant Voltage MIG		F-48
Replacement Procedures
Input Contactor (CR1) Cleaning/Replacement		F-49
SCR Rectifier Bridge Removal and Replacement		F-51
Main Transformer and Choke Removal and Replacement		F-54
Retest After Repair		F-57