Lincoln Electric DC-655 service manual Figure F.15 Heat Sink Test Points

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F-37

F-37

TROUBLESHOOTING & REPAIR

STATIC SCR TEST (continued)

FIGURE F.15 – HEAT SINK TEST POINTS

ANODE

CATHODE

REMOVE

INSULATING

PAINT

6. If a high or infinite resistance is indicated for	8. Replace plug J9 into the thermal fan/snub-
both steps #4 and #5, SCR1 is not shorted.	ber board and plug J5 into the firing board.
7. If a low resistance is indicated in either steps	NOTE: To further check the SCRs’ functions use
#4 or #5, there is a shorted SCR in the out-	an SCR tester and proceed to the Active SCR
put rectifier bridge. Repeat steps #4 and #5	Test.
for each of the six SCRs. It may be neces-
sary to disconnect the transformer sec-
ondary leads from the rectifier assembly to
isolate the defective SCR(s). See the Wiring
Diagram.

IDEALARC DC-655

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Contents Idealarc DC-655 California Proposition 65 Warnings SafetyElectric Shock can kill Cylinder may explode if damaged Précautions DE Sûreté Master Table of Contents for ALL Sections Table of Contents Installation Section Technical Specifications DC-655 InstallationInput Power Three Phase Select Suitable Location Safety PrecautionsElectrical Input Connections Input Supply Connection Diagram Input Power Supply ConnectionsElectrode and Work Cables Output ConnectionsAuxiliary Power Table Auxiliary Power Control ConnectionsTerminal Strip 2 T.S.2 Terminal Strip 1 T.S.1Table of Contents Operation Section Operating Instructions OPERATIONB-2Recommended Processes and Equipment Design Features AdvantagesOperation General DescriptionDC-655 Figure B.2 Lower Case Front Controls & Connections Machine Protection Auxiliary PowerCase Back Connections Thermal Shutdown Remote Control Leads Fault Protection SHUTDOWN1Over Current Protection Shutdown Welding Performance CV Mode CURRENT-LIMITINGCC Mode HOT Start CC Mode ARC Force CC Mode ARC GougingTable of Contents Accessories Remote Output Control Field Installed OptionsSEMI-AUTOMATIC Wire Feeders 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 Electric Shock can kill General MaintenanceFigure 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 Figure E.4 SCR Operation SCR OperationIdealarc DC-655 Table of Contents Troubleshooting & Repair Section HOW to USE Troubleshooting Guide Troubleshooting & RepairPC Board Troubleshooting Procedures Troubleshooting Guide Control Board LED ChartPerform the SCR Bridge Test LED ChartOutput Bridge TestMain See the Idle Shut Down TimerTransformer Test Function Problems Thermal Fan/Snubber PC Troubleshooting & Repair Welding Problems See the Control Board Mode Current LimitingTest Description Internal Trigger Circuit TestMaterials Needed Trigger Diagram Test ProcedureInternal Trigger Circuit Test Section Simplified Trigger Diagram. If a resistanceFigure F.3 Simplified Trigger Diagram Firing Board Test Figure F.4 Firing Board Trigger Circuit Test Points and LEDs Firing Board TestMain Transformer Test Figure F.5 14-PIN Receptacle Figure F.4 Main Transformer T1 Voltage Test Figure F.6 Input Contactor and Primary Leads Main Transformer T1 Voltage TestTroubleshooting & Repair Figure F.8 Terminal Strip Figure F.9 Firing Board Plug J5 Pins Control Transformer T2 Test Figure F.10 Control Transformer Control Transformer T2 TestHigh Voltage is present at Control Board Transformer T3 Test Perform the Control Transformer T2 Test Control Board Transformer T3 TestInput Contactor Test Transformer T2 Test Input Contactor Test Figure F.13 Input Contactor Test Connections Test for Contact ContinuityStatic 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 LED Functions and Indications Thermal FAN/SNUBBER Board LED ChartLED # LED Functions and Indications Control Board LED ChartScope Settings Normal Open Circuit Voltage Waveform Constant Voltage MIG Maximum Output Setting no LoadMinimum Output Setting no Load Troubleshooting & Repair Typical SCR Gate Voltage Waveform Constant Voltage MIG Installation Description Input Contactor CR1 CLEANING/REPLACEMENTCleaning Procedure Input Contactor CR1 CLEANING/REPLACEMENTSCR Rectifier Bridge Removal Replacement Procedure Procedure Replacement ProcedureSCR Rectifier Bridge Removal SCR Rectifier Bridge LEG Assembly Mounting Brackets ReassemblyMain Transformer and Choke Removal Replacement Procedure Output Choke Removal Main Transformer and Choke RemovalMain Transformer Removal Input Idle Amps and Watts Retest After RepairSVM 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