Agilent Technologies AGILENT MODELS 6023A and 6028A service manual Troubleshooting Bias Supplies

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Troubleshooting Bias Supplies

+5V on A2 Control Board. The PWM A2U6 includes a clock generator (45KHz set by A2R53 and A2C26), and a current limit (2Adc set by 0.15Vdc across A2R50). It turns off each output pulse using the difference between the voltage at voltage divider A2R46-A2R47 and the 2.5Vdc set by voltage regulator A2U5.

Circuit Included. + 5Vdc bias supply circuitry from connector pin A2P1-15 through jumper A2W3 on A2 control board.

Setup. The Main Troubleshooting Setup, page 29. Apply the ac mains voltage to the bias transformer, and set the external supply to 0Vdc.

Input:
NODE +	MEASUREMENT	SOURCE
A2J3-22	≈ 20Vdc	A1CR6,A1CR7
Outputs
NODE	MEASUREMENT
A2U6-6	≈ 2 to 4Vdc sawtooth, 45KHz
A2U6-12,13	≈ 19Vpk, 15∝s pulses, 45KHz
A2Q3 (emit)	≈ 20Vpk, 5∝s pulses, 45KHz
A2U5 (OUT)	2.5 Vdc
A2R50, A2CR11 (anode)	≈ 0 > V > -0.07Vdc
A2R161, A2R163	2.5 Vdc

To check if load on + 5 V is shorted, remove jumper A2W3

Table 3-4. A3 Front-Panel Board Failure Symptoms

SYMPTOMS	DEFECTIVE CIRCUIT	CHECK COMPONENTS
Error when pressing DISPLAY SETTINGS	Limits display.	A3U1, A3U9
Error in VOLTS or AMPS	Input ranging or DVMS.	A3U1,A3U2,A3U4,A3U5,A3U7
* one or more display digits out	Display LEDs.	A3DS1 through A3DS7
Unable to adjust VOLTAGE or CURRENT	Potentiometers.	A3R4, A3R5
or always max
VOLTS decimal point error	Decimal drivers.	A3U6

*Note that the Volts and Amps tests (Table 3-3 pins 5 and 6) verify that all the current and voltage display segments light except for the decimal points.

Table 3 5. Performance Failure Symptoms

SYMPTOMS	DEFECTIVE	CHECK FUNCTIONAL CIRCUITS
	BOARD
Unexplained OVP shutdowns	A2	OVP Circuit, CV Circuit

No current limit	A2	CC Circuit

Max current < 30Adc	A2	CC Clamp, CC Circuit

Max power < specified	A2, A1	Power Limit, 20KHz clock, transformer A1T1

Max voltage < 20Vdc	A2, A1	CV Circuit, diodes A1CR1-CR4

Cycles on & off randomly	A2, A1	AC-Surge-&-Dropout Detector, Mains Voltage
		Select switch A1S2

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Contents Autoranging Certification Safety Summary Printing History Safety Symbol DefinitionsTable of Contents Replaceable Parts Circuit Diagrams TroubleshootingSafety Considerations ScopeItem Description Manual RevisionsIntroduction Calibration ProcedureTest Equipment Required Operation Verification TestsTest Equipment Required Type Required Characteristics USE Recommended Model1KVA Initial SetupMON Calibration ProcedureIout VoutPerformance Tests Measurement TechniquesCR7 Constant Voltage CV Tests Current-Monitoring Resistor SetupBasic Test Setup RMS Measurement Test Setup, CV Pard Test Peak-To-Peak Measurement Test Setup, CV Pard Test KHz Noise, CV Peak-to-Peak Pard 6023A 6028ALoad Transient Recovery Waveform Constant Current CC Tests CC Pard Test Setup Initial Troubleshooting Procedures TroubleshootingPIN no Signal Name Control Board Test Connector, A2J7Vdc WAVEFORM/CONDITIONS SourceElectrostatic Protection Repair and ReplacementA2 Control Board Removal Overall Troubleshooting Procedure A4 Power Mesh Board RemovalA3 Front-Panel Board Removal A1 Main Board RemovalSetup Using the TablesNode MeasurementMain Troubleshooting Setup Main Troubleshooting SetupModified Mains Cord Set For Troubleshooting Front-Panel Troubleshooting Troubleshooting No-Output FailuresPWM-ON PWM-OFF Defective Check Functional Circuits A2J7-26 A2J7-25Board Symptoms Defective Circuit Check Components Troubleshooting Bias SuppliesSymptoms Defective Check Functional Circuits Board Node + Measurement SourceNode + Measurement SourceNode + N0DE Troubleshooting AC-Turn-on Circuits Power Section BlocksSetup Measurement Source Setup MeasurementTroubleshooting PWM & Clock Relay EnablePower Limit + OUT Troubleshooting DC-To-DC ConverterPWM-ON PWM-OFFTroubleshooting CC Circuit Troubleshooting CV CircuitTroubleshooting Down Programmer Troubleshooting OVP CircuitA4U4OUT Waveforms SET Voltage Vdc Node + Page Block Diagram Overview Autoranging PowerBlock Diagram Simplified Schematic Simplified Schematic Down Programmer DC-to-DC ConverterConstant-Voltage CV Circuit Pfet Control Signals Timing DiagramConstant-Current CC Circuit Power-Limit ComparatorOvervoltage Protection OVP Circuit Control-Voltage ComparatorPulse-Width Modulator PWM Initial-Ramp CircuitBias Voltage Detector AC-Surge Dropout DetectorDisplay Circuits Second-Delay CircuitPage Reference Designators Replaceable PartsDescription Abbreviations Ordering InformationCR1 Electrical PartsCR2 CR3XA2P1 XA2P2Mechanical Parts Control Board Assembly CR3 Page Page Page VR3 VR4VR5 CR5 DS1DS5 IC A/D Cmos 3-1/2 DGT VR1VR2 Pfet NPN SIChassis Electrical TS1A2 Board Mechanical Parts A1TB1A3 Board Mechanical Parts A4 Board Mechanical PartsOption 240 240V Operation Option 220 220V 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 Specifications General InformationOption 002 Hardware Input Compliance Voltage ± Current Programming Enable Table A-1. Specifications, Option Remote ProgrammingOutput Impedance 10.2 k ohm ± 5% Temperature Coefficient Status IndicatorsPower-on Preset Remote Trip and Remote Reset TimingMaximum Output Voltage logic high + On State logic lowBias Supplies DC Output Ratings 25C ± Table A-1. Specifications, Option Pulse TimingShort Circuit Output Current Pard TypicalConnector Assembly Procedure InstallationOperation Figure A-1. Mating Connector AssemblyLocal/Remote Programming Resistance Voltage or Current Figure A-4. Calculating Value of Series Dropping Resistor Remote Resistance ProgrammingFigure A-5. Remote Resistance Programming Remote Monitoring Remote Control Status IndicatorsOvervoltage Remote ResetFigure A-8. Remote Control Power-On PresetMultiple Supply System Shutdown AC Dropout Buffer CircuitBias Supplies MaintenanceTroubleshooting Current Programming Troubleshooting Resistance and Voltage ProgrammingFigure A-11. Troubleshooting Current Programming of CV Mode Figure A-13. Troubleshooting Status Indicators Page REF. Desig Model no Description Table A-3. Replacement Parts100 101 VR9OLD Symbol NEW Symbol Indicator and Qualifier SymbolsLogic Symbols and Definitions 102 DefinitionsSchematic Diagram Notes 103 Schematic NotesFigure A-15. Option 002 Board, Component Location 104 Schematic NotesFigure A-16. Option 002 Board, Schematic Diagram 105 Page Model 6023A Model 6028A107 108 From