Lincoln Electric Essential Troubleshooting for Lincoln DC 655 Welders: Ensuring Effective Repair
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F-3

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TROUBLESHOOTING & REPAIR

PC BOARD TROUBLESHOOTING PROCEDURES

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WARNING

ELECTRIC SHOCK can kill.

•Have an electrician install and service this equipment. Turn the input power OFF at the fuse box before working on equipment. Do not touch electrically hot parts.

CAUTION

Sometimes machine failures appear to be due to PC board failures. These problems can sometimes be traced to poor electrical connections. To avoid prob- lems when troubleshooting and replacing PC boards, please use the following procedure:

1.Determine to the best of your technical ability that the PC board is the most likely component causing the failure symptom.

2.Check for loose connections at the PC board to assure that the PC board is properly connected.

3.If the problem persists, replace the suspect PC board using standard practices to avoid static electrical damage and electrical shock. Read the warning inside the static resistant bag and perform the following procedures:

PC board can be damaged by static electricity.

-Remove the PC board from the static-shielding bag and place it directly into the equipment. Don’t set the PC board on or near paper, plastic or cloth which could have a static charge. If the PC board can’t be installed immediately, put it back in the static-shield- ing bag.

-If the PC board uses protective shorting jumpers, don’t remove them until installation is complete.

-If you return a PC board to The Lincoln Electric Company for credit, it must be in the static-shielding bag. This will prevent further damage and allow prop- er failure analysis.

4.Test the machine to determine if the failure symptom has been corrected by the replacement PC board.

NOTE: It is desirable to have a spare (known good) PC board available for PC board troubleshooting.

NOTE: Allow the machine to heat up so that all electrical components can reach their operating temperature.

5.Remove the replacement PC board and substitute it with the original PC board to recreate the original problem.

a.If the original problem does not reappear by substituting the original board, then the PC board was not the problem. Continue to look for bad connections in the control wiring harness, junction blocks, and terminal strips.

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ATTENTION

Static-Sensitive

Devices

Handle only at

Static-Safe

Workstations

-Remove your body’s static charge before opening the static- shielding bag. Wear an anti-static wrist strap. For safety, use a 1 Meg ohm resistive cord connected to a grounded part of the equipment frame.

-If you don’t have a wrist strap, touch an un-painted, grounded, part of the equipment frame. Keep touching the frame to prevent static build-up. Be sure not to touch any electrically live parts at the same time.

b. If the original problem is recreated by the substitution of the original board, then the PC board was the problem. Reinstall the replacement PC board and test the machine.

6.Always indicate that this procedure was followed when warranty reports are to be submitted.

NOTE: Following this procedure and writing on the warranty report, “INSTALLED AND SWITCHED PC BOARDS TO VERIFY PROBLEM,” will help avoid denial of legitimate PC board warranty claims.

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-Tools which come in contact with the PC board must be either conductive, anti-static or static-dissipative.

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-2Operation Design Features AdvantagesGeneral 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 CC Mode HOT Start CV Mode CURRENT-LIMITINGCC Mode ARC Force CC Mode ARC Gouging Welding PerformanceTable 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 Operation Idealarc DC-655 Table of Contents Troubleshooting & Repair Section HOW to USE Troubleshooting Guide Troubleshooting & RepairPC Board Troubleshooting Procedures Troubleshooting Guide Control Board LED ChartOutput LED ChartBridge Test Perform the SCR 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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