Agilent Technologies 6634B A3 Front Panel Circuits, A2 Interface Circuits, Primary Interface

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4 - Principles of Operation

A3 Front Panel Circuits

As shown in Figure 4-1, the supply's front panel assembly contains a circuit board, a keypad, a liquid crystal display (LCD), and a rotary control (RPG) for the output voltage and current. With the exception of the RPG (A3G1), the A3 Front Panel board is an assembly-level replaceable part. A separate front panel binding post board is also included on the unit. It is also available as an assembly-level replaceable part.

The A3 front panel board contains microprocessor circuits, which decode and execute all keypad and RPG commands that are transferred to the power supply output via the serial I/O port to the primary interface circuits on the A2 interface board. The front panel microprocessor circuits also process power supply measurement and status data received on the serial I/O port. This data is displayed on the LCD.

A2 Interface Circuits

The circuits on the A2 interface board provide the interface between the GPIB interface, RS-232 interface, and front panel interface and the dc power supply. Communication between the power supply and a GPIB controller is processed by the GPIB interface and the primary microprocessor circuits on the A2 board. The A2 Interface board is assembly-level replaceable; it contains no user-replaceable parts.

With the exception of the front panel microprocessor, all digital circuits, analog-to-digital converters (ADC) and digital-to-analog converters (DAC) in the dc power supply are located on the A2 Interface board. All control signals between the A2 interface board and the A1 main board are either analog or level signals.

Primary Interface

The primary microprocessor circuits (DSP, ROM, and RAM chips) decode and execute all instructions and control all data transfers between the controller and the secondary interface. The primary microprocessor circuits also processes measurement and status data received from the secondary interface.

A Dual Asynchronous Control chip on the A2 board converts the RS-232, RI/DFI, and front panel data into the primary microprocessor's 8-bit data format. The serial data is transferred between the primary interface and the secondary interface via a serial bus and optical isolator chips. These chips isolate the primary interface circuits (referenced to earth ground) from the secondary interface circuits.

Secondary Interface

The secondary interface circuits include a programmed logic array, EEPROM, boot-ROM, 8 and 12-bit DAC circuits, and 8 and 16-bit ADC circuits. The programmed logic array translates the serial data received from the primary interface into a corresponding digital signal for the appropriate DAC/ADC circuits. The logic array is also connected directly to four DAC/ADC circuits. Under control of the logic array, the selected DAC converts the data on the bus into an analog signal. Conversely, the selected ADC converts the analog signals from the A1 board into a digital signal.

The logic array also directly receives status information from the A1 main board via three level-sensitive signal lines, which inform the array of the following operating conditions: constant voltage mode (CV_Detect*), constant current mode (CC_Detect*), negative current mode (CCN_Detect*), and overvoltage (OV_Detect*). The PM_Inhibit control signal is used to shut down the bias voltage to the output stages and keep the power supply output off. The OV_SCR* control signal is used to fire the SCR and keep the power supply output off when an overvoltage condition has occurred.

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Contents Agilent Part No Microfiche No October Warranty Information CertificationSafety Summary Before Applying PowerSafety Symbol Definitions Symbol DescriptionPrinting History Instrument IdentificationItem Description Table of Contents Initialization ROM Upgrade Disassembly ProceduresIntroduction General Schematic Notes Backdating Post-repair CalibrationPage Safety Considerations OrganizationRelated Documents ChapterRevisions Electrostatic DischargeManual Revisions Firmware RevisionsType Specifications Recommended Model IntroductionTest Equipment Required Built-in Self TestsTest Setup Measurement TechniquesOperation Verification Tests Performance TestsElectronic Load Current-Monitoring ResistorCV Setup Constant Voltage CV TestsVoltage Programming and Readback Accuracy CV Load EffectCV Source Effect CV Noise PardTransient Recovery Time CC SetupConstant Current CC Tests Current Programming and Readback AccuracyCurrent Sink -CC Operation Low Range Current Readback AccuracyCC Load and Line Regulation CC Load Effect CC Source EffectPerformance Test Equipment Form CC Noise PardPerformance Test Record Forms − 4 mV + 4 mV Model Agilent 6634B Report No Date Test Description Minimum Vout − 12 mVVout − 42 mV Iout + 0.29 mATroubleshooting Overall Troubleshooting Flow ChartsTest Equipment Required for Troubleshooting Type Purpose Recommended ModelSheet 1. Main Flowchart Sheet 2. Main Flowchart Sheet 3. Main Flowchart Sheet 4. OV at Turn-On Sheet 5. OV at Turn-On Sheet 6. FS Indicated but Fuse OK Sheet 7. No Output Voltage Sheet 8. No Output Voltage Sheet 9 No Output Voltage Sheet 10. No Current Limit Sheet 11. Unit Does Not OV Sheet 12. High Output Voltage Specific Troubleshooting Procedures Power-on Self-test FailuresSelf-Test Error Codes/Messages Error Code Description Probable CauseCV/CC Status Annunciators Troubleshooting Bias and Rail VoltagesBias and Reference Voltages Bias Test Point Common MeasurementJ307 Voltage Measurements Voltage Measurements at J307 A2 Interface to A1 Main boardDisabling Protection Features Manual Fan Speed ControlInhibit Calibration Switch Calibration PasswordPost-repair Calibration ROM Upgrade Upgrade ProcedureInitialization Identifying the FirmwareDisassembly Procedures Remote sense leads before attempting disassemblyList of Required Tools Cover, Removal and Replacement A2 Interface Board, Removal and ReplacementFront Panel Assembly, Removal and Replacement S1 Line Switch, Removal and Replacement A3 Front Panel Board, Removal and ReplacementT1 Power Transformer, Removal and Replacement A1 Main Control BoardLine Voltage Wiring Transformer WiringInterface Signals Power Supply Interface signalsConnector Signal Description A3 Front Panel Circuits A2 Interface CircuitsPrimary Interface Secondary InterfaceA2/A3 Block Diagram Power Circuits A1 Main Board CircuitsA1 Block Diagram Control Circuits Principles of Operation Page Chassis, Electrical Designator Model PartNumber Qty DescriptionChassis, Mechanical Designator Model Part Number Qty DescriptionMechanical Parts ldentification A1 Control Board PC Board Assembly Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Replaceable Parts Binding Post Option #020 A5 AC input/RFI BoardRelay Option #760 General Schematic Notes Model-dependent ComponentsDiagrams A1 Board Component Locations R434 825 R500 175 325 R435 R505 A1 Board Component Locations A4 and A6 Board Component Locations A1 Board schematic sheet A1 Board schematic sheet A1 Board schematic sheet A6 Relay Option Board schematic Index Index Manual Updates
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6632B, 6633B, 66332A, 6634B specifications

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