Lincoln Electric SVM100-A service manual Silicon Controlled Rectifier Test, Battery Test

Page 71

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TROUBLESHOOTING & REPAIR

F-30

ACTIVE SCR TEST (continued)

SW1

R2

 

 

 

 

 

 

V

 

 

R1

 

 

 

 

 

SW2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6volt

 

 

 

A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

G

Lantern

 

 

 

 

 

 

 

 

 

 

SCR

 

 

 

 

 

 

 

 

 

Battery

 

 

 

 

C

 

 

 

 

 

 

under

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

test

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R1= 4 ohms /10 watts

 

 

 

 

 

 

 

 

 

 

R2= 3 ohms/ 10 watts

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

FIGURE F.15 - SILICON CONTROLLED RECTIFIER TEST SETUP.

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SILICON CONTROLLED

RECTIFIER TEST

(Heat Sink Mounted Units)

To test SCR’s construct the circuit outlined in Figure F.15. One 6V lantern battery can be used. Resistor values are Ò10%. The voltmeter scale should be low, approximate- ly 0-5 or 0-10 volts.

BATTERY TEST

Check the battery by shorting leads (A) and

(C)and then close switch SW-1. Re-place battery if voltage is less than 4.5 volts.

1.Connect SCR into the test circuit as shown (A) lead to anode (C) lead to cathode and (G) lead to the gate.

2.Close switch SW-1 (switch SW-2 should open), voltmeter should read zero. If the voltmeter reads higher than zero the SCR is shorted.

3.With switch SW-1 closed, close switch SW-2 for two seconds and release. The voltmeter should read 3 to 6 volts before and after switch SW-2 is released. If the voltmeter does not read, or reads only while SW-2 is depressed, the SCR or battery is defective (repeat Battery Test Procedure).

4.Open switch SW-1, disconnect the gate lead (G) and reverse the (A) and (C) leads on the SCR. Close switch SW-1. The voltmeter should read zero. If the voltage is higher than zero, the SCR is shorted.

12/95 SQUARE WAVE TIG 255

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Contents Square Wave TIG Fumes and Gases can be dangerous SafetyElectric Shock can kill ARC Rays can burnWelding Sparks can cause fire or explosion Cylinder may explode if damagedMay be dangerous Electric and Magnetic FieldsSûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents for ALL Sections Installation Section Table of ContentsTechnical Specifications Square Wave TIG InstallationStacking Safety PrecautionsHigh Frequency Interference Protection Select Suitable LocationInput Supply Connections Input ConnectionsGround Connection TIG Torch Connection Reconnect ProcedureOutput Connections Stick Electrode Cable Connection Table A.1Operation Section Fumes and Gases OperationOperating Instructions General WarningsSection TOC Coolant Tion Output Polarity Do not Switch AC & DC Recti Fier Power SourceWhile Weld ING TIG Gtaw Single Phase Work ConnecRecommended Processes and Equipment Design Features AdvantagesOperational Features and Controls General DescriptionLimitations Welding CapabilityControl Panel Keys Controls and SettingsLoad Case Front ControlsTIG Welding Guidelines Accessory Operation TIG WeldingTable B.1 Recommended Polarity Settings for TIG Welding Hand and Foot Amptrol Welding OperationSquare Wave TIG 255 12/95 TIG Welding Sequence Operation 2-STEP ModeTable B.2 Typical Current Ranges 1 for Tungsten Electrodes TIG Welding Sequence Operation 4-STEP Mode AC Wave Balance and Auto Balance Auxiliary PowerAdvanced TIG Welding Features ALL MachinesOverload Protection Square Wave TIG Accessories Section Undercarriage Function AccessoriesOptions / Accessories Installation of Field Installed OptionsMaintenance Section Safety Precautions MaintenanceMaintenance Routine and Periodic MaintenanceFigure D.1 General Assembly Exploded View Square Wave TIG Theory of Operation Section Power Supply Block Logic DiagramInput Line Voltage and Main Transformer Theory of OperationOutput Rectification and Feedback Control High Voltage / High Frequency Circuit DC Welding Circuit DC Welding OutputAC Welding Circuit AC Welding OutputSCR Operation Square Wave TIG SCR OperationThermal Protection Troubleshooting & Repair Section HOW to USE Troubleshooting Guide 1TROUBLESHOOTING & RepairPC Board Troubleshooting Procedures Troubleshooting & RepairOutput Problems Troubleshooting Guide12/95 Square Wave TIG Troubleshooting & Repair Recommended Course of Action Problems SymptomsPossible Areas of Misadjustments Function Problems Troubleshooting Guide Troubleshooting & Repair TIG Mode Problems Troubleshooting & Repair Troubleshooting Guide TIG Welding Problems Troubleshooting & Repair Stick Welding Problems Figure F.1 Control Board Connectors PC Board Connector LocationsMaterials Needed Control Transformer T2 Voltage TestTest Description Control BOX Test ProcedureFigure F.4 Control Board and Transformer Control Transformer T2 Voltage TestPROTECTION/SNUBBER Board Continuity Test PROTECTION/SNUBBER Board Continuity Test Table F.6 Square Wave TIG Figure F.6 PROTECTION/SNUBBER Board Test PointsARC Start Trigger Circuit Test ARC Start Trigger Circuit Test Figure F.9 PROTECTION/SNUBBER Board Test Points Static SCR Test Figure F.11 Protection Board Plug Locations Static SCR TestActive SCR Test Figure F.13 PROTECTION/SNUBBER Board Plug Locations Active SCR TestSilicon Controlled Rectifier Test Battery TestScope Settings Normal Open Circuit Voltage Waveform DC Stick ModeNormal Open Circuit Voltage Waveform AC Stick Mode Normal Open Circuit Voltage Waveform DC TIG Mode Normal Open Circuit Voltage Waveform AC TIG Mode Machine Loaded to 200 Amps AT 50 VDC Typical Output Voltage Waveform Machine Loaded DC TIG ModeMachine Loaded to 200 Amps AT 46 VAC AC TIG Mode Auto Balance onMachine Loaded to 50 Amps AT 26VAC Typical SCR Gate Voltage Waveform Volts 5msVolts 2ms Troubleshooting & Repair Tools Required FAN Motor and Blade RemovalFAN Motor and Blade Removal Materials Required SCR Heat Sink Assembly RemovalSCR Heat Sink Assembly Removal Recommended Meters for Machine Output Tests Retest After RepairInput Idle Amps Figure F.16 Transformer Lead Test Points Retest After Repair cont’dElectrical Diagrams Electrical Diagrams PTC1,PTC2 THERMISTOR-PTC,56 OHMS,90MA Control Board G2150Control Board G2150 cont’d Square Wave TIG PROTECTION/SNUBBER Board L9255 CAPACITOR-CEMO,4700P,50V,10% Square Wave TIG Wiring Diagram Square Wave TIG 6 a 0 a 7 a 8 a 3 C Machine Schematic Square Wave TIGA C C T G2150Y P a D Control Board Schematic Square Wave TIG 255 cont’d G2150PROTECTION/SNUBBER Board Schematic Square Wave TIG 255 L9255 Keypad LED Board Square Wave TIG 255 L9212