Lincoln Electric DC-655 service manual Figure F.4

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F-21

F-21

TROUBLESHOOTING & REPAIR

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12.Test for 9.5 VDC to 11.0 VDC between leads #231 and #215 on the firing board.

Make sure the Mode Switch (SW2) is in a constant voltage (CV) position.

Locate plug J5 on the firing board. Locate leads #231 (pin-13) and #215 (pin-12). See

Figure F.4.

Connect a jumper wire from pin C (lead #2) to pin D (lead #4) at the 14-pin receptacle. (Or put the Output Terminal Switch in the ON position.) This should initiate machine output at the welding terminals.

Rotate the Output Control (R1) clockwise and counter-clockwise. The DC voltage between leads #231 and #215 should vary from 9.5 VDC to 11.0 VDC as the control is turned from minimum to maximum. If the voltage varies and LEDs 1 through 6 do NOT vary in brightness, the firing board may be faulty.

If the voltage does NOT vary, the control board, control potentiometer or associated leads may be faulty. See the Wiring Diagram.

13.Test for approximately 5.5 VDC between leads #231 and #215 on the firing board. See Figure F.4.

Put the Mode Switch (SW2) in the constant current (CC) position.

Rotate the Output Control (R1) clockwise and counter-clockwise. The DC voltage between leads #231 and #215 should be constant at approximately 5.5 VDC. This voltage should not vary when the output control is turned.

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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 Safety Precautions Select Suitable LocationElectrical 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 Auxiliary Power Machine ProtectionCase Back Connections Remote Control Leads Fault Protection SHUTDOWN1 Thermal ShutdownOver 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 TestSee the Idle Shut Down Timer MainTransformer Test Function Problems Thermal Fan/Snubber PC Troubleshooting & Repair Welding Problems See the Control Board Mode Current LimitingInternal Trigger Circuit Test Test DescriptionMaterials Needed Test Procedure Trigger DiagramInternal 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 TestFigure 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 Replacement Procedure 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

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