Lincoln Electric DC-655 service manual Figure F.17 Heat Sink Test Points Anode Cathode

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F-40

F-40

TROUBLESHOOTING & REPAIR

ACTIVE SCR TEST (continued)

FIGURE F.17 – HEAT SINK TEST POINTS

ANODE

CATHODE

 

SW1

R2

 

+

V

R1

 

 

SW2

 

 

 

6 VOLT

A

 

R1 = 4 ohms/10 watts

 

G

R2 = 3 ohms/10 watts

LANTERN

SCR

BATTERY

 

 

UNDER

C

 

 

TEST

 

 

 

 

To test SCRs construct the circuit outlined above. Resistor values are plus or minus ten precent. The voltmeter scale should be low, approximately 0-5 or 0-10 volts DC.

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4.Construct the circuit shown in Figure F.17. One 6-volt lantern battery can be used. Set the voltmeter scale low, at approximately 0- 5 volts or 0-10 volts.

a.Test the voltage level of the battery. Short leads (A) and (C). Close switch SW-1. Battery voltage should be 4.5 volts or higher. If lower, replace the bat- tery.

5.Connect the Tester to SCR 1 as shown in Figure F.17.

a.Connect Tester lead (A) to the anode.

b.Connect Tester lead (C) to the cathode.

c.Connect Tester lead (G) to the gate.

6.Close switch SW-1.

NOTE: Switch SW-2 should be open.

7.Read the meter for zero voltage.

a.If the voltage reading is higher than zero, the SCR is shorted.

8.Close or keep closed switch SW-1.

9.Close switch SW-2 for 2 seconds and release and read the meter.

a.If the voltage is 3-6 volts while the switch is closed and after the switch is open, the SCR is functioning.

b.If the voltage is 3-6 volts only when the switch is closed or there is no voltage when the switch is closed, the SCR is defective.

NOTE: Be sure the battery is functioning properly. A low battery can affect the results of the test. Repeat the battery test procedure in Step 4 if needed.

10.Open switch SW-1.

11.Reconnect the Tester leads. See Figure F.17.

a.Connect Tester lead (A) to the cathode.

b.Connect Tester lead (C) to the anode.

c.Disconnect Test lead (G) from the gate.

12.Close switch SW-1.

13.Read the meter for zero voltage.

a.If the voltage is zero, the SCR is func- tioning.

b.If the voltage is higher than zero, the SCR is shorted.

14.Perform the Active Test Procedure outlined in Steps 5-13 for SCRs 2-6.

15.Replace all SCR assemblies that do not pass the above tests.

16.Plug J9 onto the thermal fan/snubber board and plug J5 into the firing board.

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 Select Suitable Location Safety PrecautionsElectrical 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 Machine Protection Auxiliary PowerCase Back Connections Thermal Shutdown Remote Control Leads Fault Protection SHUTDOWN1Over 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 TestMain See the Idle Shut Down TimerTransformer Test Function Problems Thermal Fan/Snubber PC Troubleshooting & Repair Welding Problems Mode Current Limiting See the Control BoardTest Description Internal Trigger Circuit TestMaterials Needed Trigger Diagram Test ProcedureInternal 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 Procedure Replacement 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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