Thermal Comfort 3000 manual Pilot Circuit Check, High Voltage is present

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The PWM compares shunt amp output on J9-5 with the current control signal (3.3 - 10 VDC) from the re- mote (J7-18) or the panel control (J10-15). A faulty shunt amp could cause the output, normally 0 VDC with no cutting arc, to go higher, shutting off the PWM and thus producing no DC. If the shunt amp ribbon connector is disconnected or pin 1 is open, approxi- mately 12 VDC is applied to J9-5, shutting down the PWM in the same manner as a shunt amp failure.

The Switching Control PC Board sends pulses (+15

V)to the Driver PC Board on J8-1 and J8-3. The width of these pulses controls the on-time of Q1. The pulses are best observed with an oscilloscope, but an AC voltmeter should read about 6 to 7 VAC from J8-2 to both J8-1 and J8-3. If 0 VAC is measured at both J8-1 and J8-3, with the enables (J10-9 and J10-23) and shunt amp (J9-5) input low, replace the Switching Control PC Board.

WARNING

Both base and emitter are at -320 VDC potential. Use extreme caution when testing Driver PC Board output.

If switching pulses are present at J8-1 and J8-3, check the Driver PC Board output between J27-3, Q1 base, and J27-2, Q1 emitter.

The Driver PC Board output, J27-3 (Q1 base) to J27-2 (Q1 emitter), should measure about 1 VAC. If volt- age measures 0 to -4 VDC (+ lead on J27-3) replace Driver PC Board. If switching pulses are not present (start signal OFF), -4 VDC is normal, Driver PC Board should be replaced.

N. Pilot Circuit Check

The pilot is ignited by a high frequency spark gener- ated in the Arc Starter Box. The Arc Starter Box re- quires a 24 VAC supply which should always be present and a torch tip to electrode voltage greater than 220 vdc. When the PCR contactor closes, power supply open circuit voltage (280-350 volts) is con- nected across the torch plus (tip) and minus (elec- trode). Once the pilot starts the voltage drops to un- der 220v shutting off the arc starter.

If the front panel PILOT led is on indicating drive to the PCR contactor but there are no sparks at the spark gap in the arc starter box, first confirm that there is open circuit voltage (OCV) of 280-350 vdc between torch “NEG-” and the work lead then measure the voltage at the torch bulkhead (marked “NEG-” and “POS+”). If it is low, zero to 50v, the torch is probably

shorted (pilot resistors will get very hot). If it is be- tween 100 and 200v PCR contactor is probably not closing. If it measures the same as the OCV the arc starter box may be defective.

For a shorted torch remove the consumable parts and check for damage, remove the head from the mount- ing tube and check for arcing. The short may also be internal to the head and it may or may not be measur- able with an ohmmeter. Sometimes the only way to be sure is replace the head.

If the front panel PILOT indicator is OFF check the CSR indicator, D5, on the Logic PC Board. It should be OFF. If it is ON the Switching Control PC Board may be falsely indicating main arc transfer. Check for zero volts on the Switching Control PC Board at J9-5. If it does not measure zero the Shunt Amp which should have no output is defective. Otherwise the Switching Control PC Board is faulty. If the Logic PC Board CSR indicator is OFF and PILOT indicator is OFF, the Logic PC Board is faulty.

If PILOT indicator is ON and PCR is not closing, check for 120 VAC between wire #110 and J2-1 on the Logic PC Board.

NOTE

Refer to Appendix VI for 120 VAC Circuit Dia- gram.

If not present, replace the Logic PC Board. If 120 VAC is present, check to see if it is at the PCR coil. If volt- age is present, the contactor is faulty.

WARNING

High Voltage is present.

For the Arc Starter Box confirm that the OCV mea- sured at the torch bulkhead is also preset at E1 and E2 on the Arc Starter PC Board, if not the torch leads ex- tension may be open. Check for 24 VAC from J1-1 to J1-3 on the Arc Starter PC Board (see note).

NOTE

Later versions of the Arc Starter Box have a 24 VAC indicator on the Arc Starter PC Board. The indicator will be ON when the 24 VAC is present.

If both OCV and 24 VAC are present, and no sparks are being generated, the Arc Starter PC Board is de- fective.

SERVICE TROUBLESHOOTING

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Manual 0-2533

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Contents
Merlin October 6Page Table of Contents Table of Contents Important Safety Precautions Section General InformationPublications Fire and ExplosionPrecautions De Securite Importantes AvertissementChoc Electrique Documents De Reference BruitGeneral Information National Standard and Technical Specifications Declaration of ConformityStatement of Warranty LaborGeneral Service Philosophy Service ResponsibilitiesSection Introduction Scope Of ManualIntroduction General Description Specifications & Design FeaturesSection Introduction Description Input and Output Power Theory Of OperationPlasma Arc Cutting and Gouging Pilot ArcOptions And Accessories Hour/Counter Meters Plasma/Secondary Gas ControlIntroduction Section Service Troubleshooting DiagnosticsPeriodic Inspection & Procedures System Theory Coolant Level and ConductivityDraining Coolant Circuit DescriptionSwitch-Mode Power Supply Operation Switching Control PC BoardRemote Control Logic PC Board FunctionsTroubleshooting Guide Troubleshooting and RepairAdvanced Troubleshooting Standoff ControlHow to use this Guide Fuse blown at disconnect when primary power is connected Temp indicator on redCoolant indicator off Coolant conductivity indicator offNo pilot arc Pilot indicator on PCR energized Weak or sputtering pilotVoltage Selection PC Board Check Test ProceduresEnable Circuit Tests Diode Check Blown Fuse F1 or F2 Motor Control Contactor Check MC1 or MC2 Thermal Sensing Circuit Check Pressure Sensing CircuitGas Solenoid Circuits Coolant Flow Sensor Circuit CheckRefer to Appendix IX for Start Circuit Diagram Power Supply Start CircuitRemote Control Start Circuit Switching Control Check Q1 Q1 LocationPilot Circuit Check High Voltage is presentCurrent Control, Display and CSD checks Tip Drag CircuitFront Panel Current Control Remote Current ControlVolt Bias Test Corner Slowdown CSDOK-To-Move Tests Pilot Resistor AdjustmentRefer to Appendix XII for OK-To-Move Circuit Diagram Service Troubleshooting Section Repairs & Replacement Procedures Anti-Static Handling ProceduresParts Replacement General Information ProcedureExternal Parts Replacement Handle ReplacementLeft/Right Side Panel Replacement Top Panel ReplacementAccess Panel Parts Replacement Front Panel/Chassis Parts ReplacementRear Panel Parts Replacement Three-Phase Contactor Replacement Voltage Selection PC Board ReplacementGas Solenoid Assembly Replacement Secondary Water Solenoid Valve Assembly ReplacementConductivity Sensor Assembly Replacement Coolant Tank ReplacementFlow Switch Assembly Replacement Base Assembly Parts Replacement Secondary Water Check Valve ReplacementDC Inductor L2 Assembly Replacement 29KVA Transformer T1 Assembly ReplacementUpper Chassis Parts Replacement Main Contactor W1 or W2 ReplacementMotor M1 Assembly Replacement Pump Assembly ReplacementBxbx Auxiliary Transformer T3 Assembly Replacement Do not damage HeatsinkPressure Gauge Replacement Coolant Pressure Gauge ReplacementPressure Switch Replacement Plasma or Secondary Gas Input Fitting ReplacementFuse F1 and F2 Replacement Plasma or Secondary Regulator Assembly ReplacementControl Logic PC Board Assembly Replacement Switching Control PC Board Assembly ReplacementMain Heatsink Assembly Parts Replacement Secondary Gas Check Valve ReplacementAmp STR. Diode Replacement Diodes can overheat if not properly installedAmp STR Diode Replacement Relay ReplacementAmp REV Diode Replacement Hose Assembly Replacements Drain the coolant from the Coolant Tank per Sec- tion 4.02-F Replacement Procedures Replacement Procedures Section Parts Lists Parts List BreakdownOrdering Information ReturnsExternal Power Supply Replacement Parts List Item # Qty Description Catalog #Access Panel Replacement Parts Front Panel/Chassis Replacement Parts 01217 Rear Panel Replacement Parts 1323 Base Assembly Replacement Parts 00894 Upper Chassis Replacement Parts 01226 Main Heatsink Assembly Replacement Parts 00971 Power Supply Options And Accessories 01218 Parts Lists Appendix I Input Wiring Requirements LtsAppendix II Sequence of Operation Block Diagram ActionAppendix III Typical Mechanized System Cable Connections System With Standoff Control SC11 And Gas Control GC3000Remote Cables Appendix V CNC Interface Appendix VI 120 VAC Circuit Diagram Appendix VII Ladder Diagram 15 VDC Appendix Viii Signal Flow Block Diagram Appendix IX Start Circuit Diargram Appendix X Current Control / Display Circuit Diagram Appendix XI CSD Corner Slowdown Circuit Diagram Appendix XII OK-TO-MOVE Circuit Diagram OK OUTXiii Hose BlockAppendix XIV System Schematic Appendix Daily Operational Checks or Every Six Arc Hours Weekly or Every 30 Arc HoursSix Months or Every 720 Arc Hours Twelve Months or Every 1500 Arc Hours
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