Agilent AGILENT MODELS 6023A and 6028A - Manual

7 1 Introduction Scope This manual contains information for troubleshooting the Agilent 6023A or 6028A 200W Autoranging Power Supply to thecomponent level. Wherever applicable, the service instructions given in this manual refer to pertinent information providedin the Operation Manual. Both manuals ...

8 Manual Revisions Agilent Technologies instruments are identified by a 10-digit serial number. The format is described as follows: first twoletters indicate the country of manufacture. The next four digits are a code that identify either the date of manufacture or ofa significant design change. The...

9 2 Calibration and Verification Introduction This section provides test and calibration procedures. The operation-verification tests comprise a short procedure to verifythat the unit is performing properly, without testing all specified parameters. After troubleshooting and repair of a defectivepow...

11 Table 2-1. Test Equipment Required (continued) TYPE REQUIRED CHARACTERISTICS USE RECOMMENDED MODEL Switch SPST, 30A @ 20V P DC Power Supply Voltage range: 0-60VdcCurrent range: 0-3Adc T,P Agilent 6296A Variable VoltageTransformer(autotransformer) Range greater than -13% to +6% ofnominal input AC ...

14 Table 2-3. Guide to Recalibration After Repair Printed Circuit Board Block Name Circuit Within Block Ref. Designator Perform These Procedures* A1 Main Board R3 4 A1 Main Board T1 4 then 5 A4 Power Mesh T3 4 then 5 Board A4 Power Mesh CR7 4 then 5 Board A2 Control Board Constant Voltage(CV) Circui...

15 The substitution of the load resistor requires adding a load switch to open and short the load in the CC or CV loadregulation tests. The load transient recovery time test procedure cannot be performed using load resistors. An electronic load is considerably easier to use than a load resistor. It ...

19 6023A 6028A Figure 2-6. 20KHz Noise, CV Peak-to-Peak PARD Load Transient Recovery Time . Specified for CV operation only; load transient recovery time is the time for the output voltage to return to within a specified band around its set voltage following a step change in load. Proceed as follows...

20 6023A 6028A Figure 2-7. Load Transient Recovery Waveform Temperature Coefficient. (6023A) Temperature coefficient (TC) is the change in output voltage for each ° C change in ambient temperature with constant ac line voltage, constant output voltage setting and constant load resistance. Measuretem...

21 Constant Current (CC) Tests CC Setup. Constant-current tests are analogous to constant-voltage tests, with the unit's output short circuited and the voltage set to full output to assure CC operation. Follow the general setup instructions. Load Effect (Load Regulation). Constant current load effec...

23 3 Troubleshooting Maintenance described herein is performed with power supplied to the instrument, and protective coversremoved. Such maintenance should be performed only by service-trained personnel who are aware of the hazards involved (for example, fire and electrical shock). Where maintenance...

24 Table 3-1. Control Board Test Connector, A2J7 PIN NO. SIGNAL NAME Vdc WAVEFORM/CONDITIONS SOURCE Digital-Circuits Bias & Reference Voltages 1 +5V 5.0 A2Q3 (emitter) 22 + 20V(5V UNREG) 20.0 with 120Hz & 45KHz ripple A1CR6, A1CR7 14 2.5V ref 2.50 A2U9 (OUT) 6 0.5V ref 0.50 A2R79,A2R80 Analo...

25 Electrostatic Protection The following caution outlines important precautions which should be observed when working with static sensitivecomponents in the power supply. This instrument uses components which can be damaged by static charge. Most semiconductors cansuffer serious performance degrada...

26 To avoid the possibility of personal injury, remove the power supply from operation before opening thecabinet. Turn off ac power and disconnect the line cord, load, and remote sense leads before attemptingany repair or replacement. When replacing any heatsink-mounted components except thermostat,...

27 A4 Power Mesh Board Removal After removing the inside cover, remove the A4 power mesh board by lifting, using the large aluminum heatsink as ahandle. Two connectors hold the A4 board at its bottom edge.When installing the A4 power mesh board, lower it vertically into its connectors and press in p...

28 Table 3-1 gives the signals for each of the test points on the control board test connector. This connector is provided inservice kit P/N 06033-60005. The measurements given here include bias and reference voltages as well as power supplystatus signals and waveform information. Table 3-2 provides...

29 Main Troubleshooting Setup Figure 3-1 shows the troubleshooting setup for troubleshooting all of the unit except the front-panel and initial no outputfailures (See page 31). The external power supply provides the unit's internal bus voltage. The ac mains cord connects tothe unit's A1T3 bias trans...

30 As a convenience in implementing the troubleshooting setup, prepare cord sets as shown in Figure 3-2. This facilitatesconnecting the unit's input power receptacle to the external supply and connecting the bias transformer to the ac mains. Figure 3-2. Modified Mains Cord Set For Troubleshooting Wi...

33 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 atvoltage divider A2R46-A2R47 and the 2.5...

35 Input: NODE ( + ) MEASUREMENT SOURCE A2U4 (IN), A2C16 (-) ≈ -24Vdc A1U1, AlC1 ( + ) Outputs: NODE ( + ) N0DE ( - ) MEASUREMENT A2U4 (ADJ) A2U4 (OUT) 1.25Vdc A2VR2 (cath.) A2VR2 (anode) 11.7Vdc A2R33, A2R34 A2VR2 (cath.) 2.05Vdc To check if load on -15V is shorted, remove jumper A2W3. Refer to Dow...

36 A2U18-13 cycle power five 100ms pulses then hi A2U18-12 cycle power two 200ms pulses then hi A2U18-15 cycle power transition lo to hi at 800 msec A2U17-8 cycle power transition lo to hi at 1.0 sec A2U17-11 cycle power transition lo to hi at 1.1 sec DROPOUT A2Q5 (col) (RELAY ENABLE) cycle power tr...

37 + OUT 40 10 3.8Vdc (OVERRANGE) + OUT 40 2 2.0Vdc (CV) + OUT 40 2 short A2J3-4 to A2J3-8 0.0Vdc Troubleshooting DC-To-DC Converter Parallel NOR gates A4U2A, A4U2B and A4U1A act as drivers and switch on FETs A4Q3 and A4Q4 through pulsetransformer A4T1. NOR gate A4U1B turns off the PFETs through pul...

38 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 comparesV-MON to CV PROGRAM. Innerloop Amp A2U10A stabilizes the CV loop with IVS input from A2U10C. Themeasurements below verify that the operational amplifier circuits ...

39 If the failure symptoms include output current oscillation, check if the differentiator circuit is at fault by removing resistorA2R16 (3.3M ohm ). If oscillations stop, the differentiator is probably at fault. Troubleshooting Down Programmer The down programmer decreases the output when either MA...

43 4 Principles of Operation Autoranging Power Autoranging allows the unit to be compact and light weight and yet to deliver a range of output voltage currentcombinations which otherwise would require the use of more than one supply or a higher rated-power supply. Autorangingis a name for circuitry ...

45 Control signals flow from right to left with separate circuits for constant-voltage, constant-current and power-limit control.These three control circuits jointly provide the Autoranging characteristic of Figure 4-lB. AC Turn-on Circuits limit inrushcurrent to the input filter and assure transien...

47 The unit checks that the + 5Vdc bias voltage and the ac mains voltage are within acceptable limits as part of its turn onsequence. When + 5Vdc comes up, the Bias Voltage Detector resets the Overvoltage-Protection circuit, enables the OnPulse Driver for the PFET switches, and with the AC Surge-Dro...

48 Figure 4-4. PFET Control Signals Timing Diagram Constant-Voltage (CV) Circuit The Constant-Voltage Circuit compares the output voltage to the user-set CV PROGRAM Voltage to produce the CVCONTROL Voltage. Two comparison amplifier loops accomplish the comparison. In the outerloop, CV Error Amplifie...

49 Constant-Current (CC) Circuit The Constant-Current Circuit compares the output current to the user-set CC PROGRAM Voltage to produce the CCCONTROL Voltage. As with the CV Circuit, two comparison amplifier loops accomplish the comparison. OCS is thevoltage across Current-Monitoring resistor A1R3, ...

50 A2CR24. The A2R113-A2R114 voltage divider sets the maximum CP voltage to + 1.5Vdc and assures that the diode withthe lower control voltage will be forward biased when its control voltage is less than + 1.5Vdc. As an illustration of CV-CCselection, suppose the unit is in CV operation and diode A2C...

51 by inhibiting the PWM through the DROPOUT signal from the l-Second-Delay Circuit. Mains Detect signal, which isfullwave-rectified ac from the + 5Vdc secondary of the bias-supplies transformer, senses the ac mains voltage. The DropoutDetector, including comparators A2U20A and A2U20C, operates by e...

53 5 Replaceable Parts Introduction This chapter contains information for ordering replacement parts. Table 5-3 lists parts in alpha-numeric order by referencedesignators and provides the following information: a. Reference Designators. Refer to Table 5-1. b. Agilent Model in which the particular pa...

54 Ordering Information To order a replacement part, address order or inquiry to your local Agilent Technolgies sales office. Specify the followinginformation for each part: Model, complete serial number, and any option or special modification (J) numbers of theinstrument; Agilent part number; circu...

69 6 Component Location and Circuit Diagrams This chapter contains component location diagrams, schematics, and other drawings useful for maintenance of the powersupply. Included in this section are: a. Component location illustrations (Figures 6-1 through 6-5), showing the physical location and ref...

79 A System Option 002 General Information This option facilitates the operation of the power supply in an automated system. Four major circuit blocks provide:1 ) remote analog programming of the supply's output by three different control methods; 2) signals indicating the powersupply modes and cond...

81 Table A-1. Specifications, Option 002 (continued) Voltage Range: +4.75V to 16V Current Drain: 20mA maximum Status Indicator output:Open collector output: Maximum Output Voltage (logic high) : + 16V Logic Low output: + 0.4V maximum at 8mA Remote Control (Trip, Reset, Inhibit) Control Isolator Bias...

83 Installation When installing the board, perform the following steps: a. Remove the top and inner cover of the power supply as discussed in Section 3 under Repair and Replacement. b. Remove the plate next to the barrier strip on the rear panel of the supply by unscrewing the 2 M3 screws. c. Insert...

84 Figure A-1. Mating Connector Assembly Operation The following paragraphs provide the operating instructions necessary to interface a 002-equipped power supply into anautomated system. A brief description of some circuits is also provided. The unit is shipped for front-panel operation withmode swi...

85 Figure A-2. 002 Option Rear Panel Connector J3 and Switches A1 and A2. Local/Remote Programming When switching to local/ control, remember to set Front-Panel Voltage and Current Control to safe levels. Local Programming (Figure A-3). The supply can be switched back and forth between remote and lo...

87 Figure A-4. Calculating Value of Series Dropping Resistor Remote Resistance Programming Check switches A1 and A2 on the rear panel, they must be in their correct positions for CV and CC resistance/voltageprogramming (See Figure A-2). A resistance variable from 0 to 4K ohms can be used to program ...

89 Current Programming (Figure A-7). Check switches A1 and A2 on the rear panel, they must be in the correct positions for CV and CC current programming (See Figure A-2). A current sink variable from 0 to 2mA, can be used to program theoutput voltage or current from 0 to full scale (See Figure A-7)....

91 Remote Trip. A negative-going edge applied to terminal J3-30 ( TRIP REMOTE ) will shut down the power supply, reducing the output voltage to near zero. For minimum pulse duration and timing considerations with respectto RESET REMOTE , See Table A-1. The following paragraph provides a brief circui...

93 on, it causes J3-6 ( Preset - On - Power ) to be low thus, if used, can initialize or delay a customer's system operation. AC Dropout Buffer Circuit This circuit couples, inverts and isolates the DROPOUT signal (received from the A2 Control Board) of status outputterminal J3-19 ( DROPOUT ). The d...

94 If it is necessary to have all the supplies come up simultaneously after a system shutdown, follow this procedure: a. First bring the INHIBIT REMOTE line low. b. Provide a negative-going pulse to the RESET REMOTE . c. After at least one second, return INHIBIT REMOTE to a high level. Figure A-10. ...

95 Troubleshooting Before attempting to troubleshoot the 002 Option Board, ensure that the fault is with the option itself and not with the mainpower supply. This can be accomplished by removing the top cover, inside cover and disconnecting the two ribbon cablesfrom the A2 Control board and checking...

97 Figure A-13. Troubleshooting Status Indicators To check Mode CV proceed as follows: a. Using test set-up, Figure A-13, connect to end of 2K Ω resistor to J3-36. b. Turn on power supply. c. Using "Display Setting'' set voltage and current or power supply for 1 volt and 1 amp. d. DVM should rea...

98 c. Turn on power supply. d. DVM should read approximately 5Vdc. e. Set voltage and current controls of power supply to maximum. f. Decrease resistance of electronic load until "UNREGULATED" LED on front-panel lights. a. DVM should now read between 0 and 0.4Vdc. To check LOW BIAS or AC Dro...

100 Table A-3. Replacement Parts REF. DESIG. MODEL NO. PART NO. DESCRIPTION R22 All 0686-1525 fxd. film 1.5K 5% 1/4W R23 All 0683-1535 fxd. film 15K 5% 1/4W R24 All 0683-4715 fxd. film 470 5% 1/4W R25,26 All 0683-1235 fxd. film 12K 5% 1/4W R27 All 0686-1525 fxd. film 1.5K 5% 1/4W R28 All 0683-1535 f...

107 B Backdating Manual backdating describes changes that must be made to this manual for power supplies whose serial numbers are lowerthan those listed in the title page to this manual. Look in the following table and located your Agilent Model. Then look at each serial number listed for this group...