Agilent Technologies AGILENT MODELS 6023A and 6028A service manual Troubleshooting CV Circuit

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Troubleshooting CV Circuit

V-MON, the output of CV Monitor Amp A2U7, is 1/4 the voltage between + S and - S. CV Error Amp A2U8 compares V-MON to CV PROGRAM. Innerloop Amp A2U10A stabilizes the CV loop with IVS input from A2U10C. The measurements below verify that the operational amplifier circuits provide expected positive and negative dc voltage excursion when the CV loop is open and the power mesh shut down.

Circuits Included. Constant Voltage (CV) Circuit and buffer amplifier A2U10C.

Setup. The Main Troubleshooting Setup, page 29. Apply the ac mains voltage to the bias transformer, and disconnect the external supply Remove the + S jumper and connect A2J3-2 ( + 15V) to + S. Set MODE switch settings B4, B5 and B6 all to 0. Set VP to 0Vdc by connecting to P or set VP to + 5Vdc by connecting to A2J3-1 according to SETUP below.

Outputs:
NODE ( + )	SETUP	MEASUREMENT
VM		3.75Vdc
A2U10C-8		4.7Vdc
A2U8-6	VP = 0	-14Vdc
A2U10A-1	VP = 0	-14Vdc
A2U8-6	VP = 5	4.7Vdc
A2U10A-1	VP = 5	5.1Vdc

If the failure symptoms include output voltage oscillation, check if the CV Error Amp circuit is at fault by shorting A2U8-6 to A2U8-2. If oscillations stop, the CV Error Amp circuit is probably at fault.

Troubleshooting CC Circuit

I-MON, the output of CC Monitor Amp A2U1, in volts is 1/6 the output current in amperes. CC Error Amp A2U2B compares I-MON to CC PROGRAM. Differentiator circuit A2U3D and A2U3C stabilizes the CC loop. It differentiates IVS and has a voltage gain of 16. Its output is summed with CC PROGRAM at CC Error Amp A2U2B.

The measurements below verify that the operational amplifier circuits provide expected positive and negative do voltage gain when the CC loop is open and the power mesh shut down.

Circuits Included. Constant Current (CC) Circuit on A2 control board.

Setup. The Main Troubleshooting Setup, page 29, except connect the external supply with polarity reversed to the unit's + OUT ( - ) and - OUT ( + ) terminals. Apply the ac mains voltage to the bias transformer. Set the external supply to 3.0Adc constant current with a voltage limit in the range 5 to 20Vdc.Set IP to 0Vdc by connecting to P or set IP to + 5Vdc by connecting to A2J3-1 according to SETUP below.

Outputs:
NODE ( + )	SETUP	MEASUREMENT
IM		0.50Vdc
A2U2B-7	IP = 0	-14Vdc
A2U2B-7	IP = 5	+14Vdc
A2U3D-13	+0.015Vdc
A2U3C-9	+0.015Vdc
A2U3C-8	+0.25Vdc

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Contents Autoranging Certification Safety Summary Safety Symbol Definitions Printing HistoryTable of Contents Replaceable Parts Safety Considerations TroubleshootingCircuit Diagrams ScopeManual Revisions Item DescriptionTest Equipment Required Calibration ProcedureIntroduction Operation Verification TestsType Required Characteristics USE Recommended Model Test Equipment RequiredInitial Setup 1KVACalibration Procedure MONVout IoutCR7 Performance TestsMeasurement Techniques Current-Monitoring Resistor Setup Constant Voltage CV TestsBasic Test Setup RMS Measurement Test Setup, CV Pard Test Peak-To-Peak Measurement Test Setup, CV Pard Test 6023A 6028A KHz Noise, CV Peak-to-Peak PardLoad Transient Recovery Waveform Constant Current CC Tests CC Pard Test Setup Troubleshooting Initial Troubleshooting ProceduresVdc Control Board Test Connector, A2J7PIN no Signal Name WAVEFORM/CONDITIONS SourceRepair and Replacement Electrostatic ProtectionA2 Control Board Removal A3 Front-Panel Board Removal A4 Power Mesh Board RemovalOverall Troubleshooting Procedure A1 Main Board RemovalNode Using the TablesSetup MeasurementMain Troubleshooting Setup Main Troubleshooting SetupModified Mains Cord Set For Troubleshooting Troubleshooting No-Output Failures Front-Panel TroubleshootingBoard PWM-ON PWM-OFF Defective Check Functional CircuitsA2J7-26 A2J7-25 Symptoms Defective Check Functional Circuits Board Troubleshooting Bias SuppliesSymptoms Defective Circuit Check Components Node + Measurement SourceNode + N0DE Node +Measurement Source Setup Measurement Source Power Section BlocksTroubleshooting AC-Turn-on Circuits Setup MeasurementPower Limit Troubleshooting PWM & ClockRelay Enable PWM-ON Troubleshooting DC-To-DC Converter+ OUT PWM-OFFTroubleshooting CV Circuit Troubleshooting CC CircuitA4U4OUT Troubleshooting Down ProgrammerTroubleshooting OVP Circuit Waveforms SET Voltage Vdc Node + Page Autoranging Power Block Diagram OverviewBlock Diagram Simplified Schematic Simplified Schematic DC-to-DC Converter Down ProgrammerPfet Control Signals Timing Diagram Constant-Voltage CV CircuitOvervoltage Protection OVP Circuit Power-Limit ComparatorConstant-Current CC Circuit Control-Voltage ComparatorBias Voltage Detector Initial-Ramp CircuitPulse-Width Modulator PWM AC-Surge Dropout DetectorSecond-Delay Circuit Display CircuitsPage Replaceable Parts Reference DesignatorsOrdering Information Description AbbreviationsCR2 Electrical PartsCR1 CR3Mechanical Parts XA2P1XA2P2 Control Board Assembly CR3 Page Page Page VR5 VR3VR4 DS5 CR5DS1 VR2 IC A/D Cmos 3-1/2 DGTVR1 NPN SI PfetTS1 Chassis ElectricalA3 Board Mechanical Parts A1TB1A2 Board Mechanical Parts A4 Board Mechanical PartsOption 220 220V Operation Option 240 240V OperationComponent Location and Circuit Diagrams Schematic Diagram Notes Pin locations for other semi-conductors are shown below Top View, Top Covers Removed Main Board A1 Component Location Control Board A2 Component Location Front-Panel Board A3 Component Location Power Mesh Board A4 Component Location Page Page Option 002 Hardware SpecificationsGeneral Information Output Impedance 10.2 k ohm ± 5% Temperature Coefficient Table A-1. Specifications, Option Remote ProgrammingInput Compliance Voltage ± Current Programming Enable Status IndicatorsMaximum Output Voltage logic high + Remote Trip and Remote Reset TimingPower-on Preset On State logic lowShort Circuit Output Current Table A-1. Specifications, Option Pulse TimingBias Supplies DC Output Ratings 25C ± Pard TypicalInstallation Connector Assembly ProcedureFigure A-1. Mating Connector Assembly OperationLocal/Remote Programming Resistance Voltage or Current Remote Resistance Programming Figure A-4. Calculating Value of Series Dropping ResistorFigure A-5. Remote Resistance Programming Remote Monitoring Status Indicators Remote ControlRemote Reset OvervoltagePower-On Preset Figure A-8. Remote ControlAC Dropout Buffer Circuit Multiple Supply System ShutdownMaintenance Bias SuppliesTroubleshooting Resistance and Voltage Programming Troubleshooting Current ProgrammingFigure A-11. Troubleshooting Current Programming of CV Mode Figure A-13. Troubleshooting Status Indicators Page Table A-3. Replacement Parts REF. Desig Model no Description100 VR9 101Logic Symbols and Definitions 102 Indicator and Qualifier SymbolsOLD Symbol NEW Symbol DefinitionsSchematic Notes Schematic Diagram Notes 103Schematic Notes Figure A-15. Option 002 Board, Component Location 104Figure A-16. Option 002 Board, Schematic Diagram 105 Page 107 Model 6023AModel 6028A From 108