Lincoln Electric DC-655 service manual Output, LED Chart, Perform the SCR Bridge Test

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F-6		F-6
	TROUBLESHOOTING & REPAIR
	TROUBLESHOOTING GUIDE	Observe Safety Guidelines
		detailed in the beginning of this manual.

PROBLEMS	POSSIBLE AREAS OF				RECOMMENDED
(SYMPTOMS)	MISADJUSTMENT(S)				COURSE OF ACTION

	OUTPUT PROBLEMS
The machine has welding output	1. Check the output control switch				1.	The output control potentiome-
but no control.	(SW3) for proper setting.					ter, output control switch (SW3)
	2. If a	remote	control	cable is		or associated		wiring	may be
	2. If a	remote	control	cable is		defective.	See the Wiring
	used,	make	certain	the cable		defective.	See the Wiring
	used,	make	certain	the cable		Diagram.
	and connections are good.					Diagram.
	and connections are good.
					2. Perform the Firing Board Test.
					3.	Perform the		SCR	Output
						Bridge Test.
					4. The control			board	may be
						faulty. See the Control Board
						LED Chart.

The machine does not have maxi-	1. Check the three-phase input				1.	The output control potentiome-
mum output.	lines at the DC-655.			Make cer-		ter, output control switch (SW3)
	tain the input voltages match					or associated wiring may be
	the machine’s rating and recon-					defective.	See the Wiring
	nect panel configuration.					Diagram.
	2. Put the output control switch				2.	Perform the Main Transformer
	(SW3) in the “Local” control					Test.
	position. If		the problem is		3. Perform the Firing Board Test.
	resolved, the remote unit or				3. Perform the Firing Board Test.
	resolved, the remote unit or
	wire feeder may be defective.				4.	Perform the SCR Bridge Test.
					5. The control			board	may be
						faulty. See the Control Board
						LED Chart.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con- tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-800-833-9353.

IDEALARC DC-655

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Contents Idealarc DC-655 Safety California Proposition 65 WarningsElectric Shock can kill Cylinder may explode if damaged Précautions DE Sûreté Master Table of Contents for ALL Sections Table of Contents Installation Section Installation Technical Specifications DC-655Input Power Three Phase Safety Precautions Select Suitable LocationElectrical Input Connections Input Power Supply Connections Input Supply Connection DiagramOutput Connections Electrode and Work CablesAuxiliary Power Control Connections Auxiliary Power TableTerminal Strip 1 T.S.1 Terminal Strip 2 T.S.2Table of Contents Operation Section OPERATIONB-2 Operating InstructionsDesign Features Advantages OperationGeneral Description Recommended Processes and EquipmentDC-655 Figure B.2 Lower Case Front Controls & Connections Auxiliary Power Machine ProtectionCase Back Connections Remote Control Leads Fault Protection SHUTDOWN1 Thermal ShutdownOver Current Protection Shutdown CV Mode CURRENT-LIMITING CC Mode HOT StartCC Mode ARC Force CC Mode ARC Gouging Welding PerformanceTable of Contents Accessories Field Installed Options Remote Output ControlAutomatic Wire Feeders SEMI-AUTOMATIC Wire FeedersSet the Idealarc DC-655 Power toggle Accessories Semiautomatic Wire Feeders Connecting the LN-7 to the Idealarc DC-655 Terminal Strip GND Negative Positive Figure C.4 Idealarc DC-655 Table of Contents Maintenance General Maintenance Electric Shock can killFigure D.1 General Component Locations Idealarc DC-655 Table of Contents Theory of Operation Section Theory of Operation Down Circuits Protective Devices and Shutdown Circuits SCR Operation Figure E.4 SCR OperationIdealarc DC-655 Table of Contents Troubleshooting & Repair Section Troubleshooting & Repair HOW to USE Troubleshooting Guide PC Board Troubleshooting Procedures Troubleshooting Guide Board LED Chart ControlLED Chart OutputBridge Test Perform the SCR Bridge TestSee the Idle Shut Down Timer MainTransformer Test Function Problems Thermal Fan/Snubber PC Troubleshooting & Repair Welding Problems Mode Current Limiting See the Control BoardInternal Trigger Circuit Test Test DescriptionMaterials Needed Test Procedure Trigger DiagramInternal Trigger Circuit Test Simplified Trigger Diagram. If a resistance SectionFigure F.3 Simplified Trigger Diagram Firing Board Test Firing Board Test Figure F.4 Firing Board Trigger Circuit Test Points and LEDsMain Transformer Test Figure F.5 14-PIN Receptacle Figure F.4 Main Transformer T1 Voltage Test Main Transformer T1 Voltage Test Figure F.6 Input Contactor and Primary LeadsTroubleshooting & Repair Figure F.8 Terminal Strip Figure F.9 Firing Board Plug J5 Pins Control Transformer T2 Test Control Transformer T2 Test Figure F.10 Control TransformerHigh Voltage is present at Control Board Transformer T3 Test Control Board Transformer T3 Test Perform the Control Transformer T2 TestInput Contactor Test Input Contactor Test Transformer T2 TestTest for Contact Continuity Figure F.13 Input Contactor Test ConnectionsStatic SCR Test Static SCR Test Figure F.15 Heat Sink Test Points Active SCR Test Active SCR Test Figure F.17 Heat Sink Test Points Anode Cathode Thermal FAN/SNUBBER Board LED Chart LED Functions and IndicationsControl Board LED Chart LED # LED Functions and IndicationsScope Settings Maximum Output Setting no Load Normal Open Circuit Voltage Waveform Constant Voltage MIGMinimum Output Setting no Load Troubleshooting & Repair Typical SCR Gate Voltage Waveform Constant Voltage MIG Installation Input Contactor CR1 CLEANING/REPLACEMENT DescriptionInput Contactor CR1 CLEANING/REPLACEMENT Cleaning ProcedureSCR Rectifier Bridge Removal Replacement Procedure Replacement Procedure ProcedureSCR Rectifier Bridge Removal Reassembly SCR Rectifier Bridge LEG Assembly Mounting BracketsMain Transformer and Choke Removal Replacement Procedure Main Transformer and Choke Removal Output Choke RemovalMain Transformer Removal Retest After Repair Input Idle Amps and WattsSVM Error Reporting Form Section G Electrical Diagrams Control Board Schematic G3384 Firing Board Schematic G2792 Thermal Fan/Snubber Board Schematic L10123 Control Board Layout G3385-1 Firing Board Layout G2699-2 Thermal Fan/Snubber Board Layout L10124-1 Return to Section TOC