Agilent Technologies AGILENT MODELS 6023A and 6028A Second-Delay Circuit, Display Circuits

Page 51

by inhibiting the PWM through the DROPOUT signal from the l-Second-Delay Circuit. Mains Detect signal, which is fullwave-rectified ac from the + 5Vdc secondary of the bias-supplies transformer, senses the ac mains voltage. The Dropout Detector, including comparators A2U20A and A2U20C, operates by enabling a capacitor-timing ramp when Mains-Detect ceases. Comparator A2U20D monitors the amplitude of Mains-Detect to provide ac surge voltage detection.

1-Second-Delay Circuit

The l-Second-Delay Circuit is the heart of the unit's controlled turn-on. It causes relay A1K1 to bypass inrush current-limiting resistor A1R1 one second after turn-on, and it enables the PWM 0.1 seconds later. When either the output of the AC-Surge and Dropout Detector or PCLR2 is low, NAND gate A2U11A holds the circuit reset. The circuit starts counting at 1/16 the clock frequency (1.25 kHz) when both inputs to A2U11A are high and causes Relay Enable to go high in 1.0 seconds and DROPOUT to go high in 1.1 seconds. When DROPOUT goes high, it stops the count, and it enables the PWM. option 002 uses DROPOUT in creating its DROPOUT output.

Display Circuits

Figure 4-5 is a simplified schematic for the display circuits. The named signals from the CV and CC Circuits are connected through semiconductor bilateral switches to the VOLTS digital voltage display and to the AMPS digital current display. Either a blank display or a depressing of the DISPLAY OVP switch changes the VOLTS display from low range to high range. A blank display occurs when the Voltage DVM A3U4 receives an over-range voltage, a voltage greater than 0.999Vdc. The blank display is detected by the Voltage-Range Switching Circuit. The diode-AND connection at inverting amplifier A3U9A senses when two selected segments of the 7-segment LED for the second digit are both not lighted. The detection scheme works because at least one of the selected segments is lighted for all digits 0 though 9.

The normal display is the actual output voltage and current and has bilateral switches A3U1A and A3U1D closed. Switch A3UlA connects V-MON through buffer amplifier A3U2 and range-switching bilateral switches to the VOLTS DVM. Switch A3Ul D connects I-MON through buffer amplifier A3U3A to the AMPS DVM. Depress the DISPLAY LIMITS Switch, and CV and CC PROGRAM Voltages connect through bilateral switches A3U1B and A3U1C to display the programmed output voltage and current. Depress the DISPLAY OVP Switch, and OV PROGRAM Voltage from the OVP ADJUST Control connects through buffer amplifier A3U3B and bilateral switch A3U7B to display the programmed OVP voltage limit. The CV and CC CONTROL Voltages also control the front-panel mode LEDs. When CV CONTROL Voltage is more negative than CP, transistor A2Q6C lights CV LED A3DS9 showing that the unit is operating in constant-voltage mode. When CC CONTROL is more negative than CP, transistor A2Q6F lights CC LED A3DS10 showing that the unit is operating in constant-current mode. And when both CV and CC are more positive than CP, NAND-gate A2U11C lights UNREGULATED LED A3DS11 showing the unit is operating in power-limited, unregulated mode.

51

Page 50 Page 52
Image 51
Page 50 Page 52
Contents Autoranging Certification Safety Summary Printing History Safety Symbol DefinitionsTable of Contents Replaceable Parts Scope TroubleshootingCircuit Diagrams Safety ConsiderationsItem Description Manual RevisionsOperation Verification Tests Calibration ProcedureIntroduction Test Equipment RequiredTest 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 TroubleshootingWAVEFORM/CONDITIONS Source Control Board Test Connector, A2J7PIN no Signal Name VdcElectrostatic Protection Repair and ReplacementA2 Control Board Removal A1 Main Board Removal A4 Power Mesh Board RemovalOverall Troubleshooting Procedure A3 Front-Panel Board RemovalMeasurement Using the TablesSetup NodeMain 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 Node + Measurement Source Troubleshooting Bias SuppliesSymptoms Defective Circuit Check Components Symptoms Defective Check Functional Circuits BoardNode + Measurement SourceNode + N0DE Setup Measurement Power Section BlocksTroubleshooting AC-Turn-on Circuits Setup Measurement SourceTroubleshooting PWM & Clock Relay EnablePower Limit PWM-OFF Troubleshooting DC-To-DC Converter+ OUT PWM-ONTroubleshooting 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 DiagramControl-Voltage Comparator Power-Limit ComparatorConstant-Current CC Circuit Overvoltage Protection OVP CircuitAC-Surge Dropout Detector Initial-Ramp CircuitPulse-Width Modulator PWM Bias Voltage DetectorDisplay Circuits Second-Delay CircuitPage Reference Designators Replaceable PartsDescription Abbreviations Ordering InformationCR3 Electrical PartsCR1 CR2XA2P1 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 TS1A4 Board Mechanical Parts A1TB1A2 Board Mechanical Parts A3 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 Status Indicators Table A-1. Specifications, Option Remote ProgrammingInput Compliance Voltage ± Current Programming Enable Output Impedance 10.2 k ohm ± 5% Temperature CoefficientOn State logic low Remote Trip and Remote Reset TimingPower-on Preset Maximum Output Voltage logic high +Pard Typical Table A-1. Specifications, Option Pulse TimingBias Supplies DC Output Ratings 25C ± Short Circuit Output CurrentConnector 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 VR9Definitions Indicator and Qualifier SymbolsOLD Symbol NEW Symbol Logic Symbols and Definitions 102Schematic 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
Top Page Image Contents