Agilent Technologies E3615A, E3614A, E3617A, E3616A service manual Service Information

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SERVICE INFORMATION

Figure A-1. Block Diagram

PRINCIPLES OF OPERATION

(Block Diagram Overview)

Throughout this discussion, refer to both the block diagram of Figure A-1 and the schematic diagrams at the rear of the manual. The input ac line voltage is first applied to the prereg- ulator which operates in conjunction with the SCR control cir- cuit (preregulator control circuit) to rectify the tap switched AC voltage. This preregulator minimizes the power dissipated in the series regulating elements by controlling the dc level across the input filter capacitor, depending on the output volt- age.

To achieve this, tap switching is accomplished by four SCRs and one bridge diode (CR10, CR12, CR15, CR18 and CR13) and the SCR control circuit. By selecting different SCR firing combinations from SCR control circuit, these circuits allow the input capacitors (C7 and C8) to charge to one of four discrete voltage levels, depending on the output voltage required.

The main secondary winding of the power transformer has three sections (N1, N2, and N3), each of which has a different turns ratio with respect to the primary winding. At the begin- ning of each half-cycle of the input ac, the control circuit determines whether one pair, both or none of the SCR will be fired. If neither SCR is fired, the bridge diode (CR13) receives an ac input voltage that is determined by N1 turns and the input capacitors charge to a corresponding level. If SCR CR15 and CR18 are fired, input capacitors charge to the volt- age determined by N1+N2 turns. Similarly, if CR10 and CR12 are fired the capacitors are charged by N1 + N3. Finally, if all SCRs are fired simultaneously, input capacitors charge to its highest voltage level determined by N1 + N2 + N3 turns.

The SCR control circuit determines which SCRs are to be fired by monitoring the output voltage and comparing these values against a set of three internally derived reference lev- els. These three reference levels are translated into boundary lines to allow the output characteristic to be mapped into four operating regions (Figure A-2). The boundary lines, which are invisible to the user, are divided into four operating regions (V1, V2, V3, and V4) to minimize the power dissipation in the

A-1

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Contents April Agilent E361xA 60W Bench Series DC Power SuppliesSafety Summary Operating Instructions General Information Line Fuse Operating Temperature RangeMeter Programming Resolution Temperature CoefficientInitial Inspection InstallationInstallation Data Input Power RequirementsTURN-ON Checkout Procedure Power CordOperating Instructions Operation Beyond Rated Output Local Operating ModeConnecting Loads Operating ModesRemote Operating Modes Remote Voltage SensingRemote Analog Voltage Programming MULTIPLE-SUPPLY Operation Normal Parallel OperationAUTO-PARALLEL Operation Gramming according to the remote-programming instructions Normal Series OperationTotal output voltage to ground must not exceed 240 Vdc AUTO-SERIES Operation= slave output voltage AUTO-TRACKING OperatonLoad Considerations Service Information Maintenance Test Equipment RequiredOperation Verification Tests Type Required Characteristics USE Recommended Model Performance TestsMeasurement Techniques Load Transient Response Time Constant Voltage CV TestsLoad Regulation Load Effect Line Regulation Source EffectPARDRipple and Noise Pardrms MeasurementPARDPeak-to-Peak Measurement CV Drift Stability Constant Current CC TestsCC Drift Stability Adjustment and Calibration ProcedureRegulating Loop Troubles TroubleshootingOverall Troubleshooting Procedure Reference and Bias CircuitOvervoltage Protection Circuit Troubles Symptom Checks and Probable CausesStep Action Response Probable Cause Step Measure Response Probable Cause Replaceable Parts Table A-10. Replaceable Parts List Table A-10. Replaceable Parts List Contd R28,111 0698-3228 Resistor 49.9K +-1% .125W TF TC=0+-100 RESISTOR-VAR 10K +-10% ALL IC V RGLTR-FXD-POS 4.8/5.2V TO-220 PKG ALL DIODE-GEN PRP 180V 200MA DO-35 ALL Table A-11. Component Value Model Page Page Page Page Manual Supplement T E Constant Voltage ModeProgramming Voltage Common to the Minus Output Alternative Voltage Programming Using ResistorsProgramming Voltage Common to the Minus Output Constant Current with Voltage Programming Constant Current ModeCurrent Monitoring Remote Resistor Programming, Constant Voltage Remote Resistor Programming ConnectionsRemote Resistor Programming, Constant Current Certification Declaration of Conformity