Lincoln Electric DC-655 service manual Static SCR Test, Test Procedure

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F-36

F-36

TROUBLESHOOTING & REPAIR

STATIC SCR TEST (continued)

FIGURE F.14 – THERMAL FAN/SNUBBER BOARD AND FIRING BOARD PLUG LOCATIONS

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THERMAL FAN / SNUBBER

LED2

LED5

LED1

L10124-[ ]

LED6

LED4

LED3

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PLUG J9

LED7	LED8	LED9		J5
				J5
LED1		LED2	G2699-[ ]
			G2699-[ ]
			LED10	J6
			LED10
LED3		LED4		J7
		LED6		J4
LED5		LED6
LED5
			FIRING BOARD

TEST PROCEDURE

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1.Disconnect the main AC input power to the DC-655 machine.

2.Locate and disconnect plug J9 from the thermal fan/snubber board and plug J5 from the firing board. See Figure F.14.

3.Remove the red insulating paint from the heat sink test points. See Figure F.15. DO NOT DISASSEMBLE THE HEAT SINKS.

4.Test for high or infinite resistance from the anode to the cathode of SCR1. See Figure F.15. Use an analog ohmmeter (multimeter).

5.Test for high or infinite resistance from the cathode to the anode of SCR1 by reversing the meter leads. See Figure F.15.

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 InstructionsGeneral Description Design Features AdvantagesOperation 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 CC Mode ARC Force CC Mode ARC Gouging CV Mode CURRENT-LIMITINGCC Mode HOT Start 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 GuidePC Board Troubleshooting Procedures Troubleshooting Guide Board LED Chart ControlBridge Test LED ChartOutput 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

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