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1. e Remove the short circuit SET LIMIT CONTROL VOLTAGE AND CURRENT To preset the output Voltage and Current proceed as follows a Set the OUTPUT switch to OFF position JBL Release Position b Press the LIMIT switch and adjust the desired output voltage with the VOLTAGE control potentiometers mk c Release the LIMIT switch set the OUTPUT switch to ON position and check the output voltage on the voltmeter IM d Set OUTPUT switch to OFF position HL e Press the LIMIT switch and adjust the desired output current limit with the CURRENT control potentiometers f Release the LIMIT switch set the OUTPUT switch to ON position and check the output current on the ammeter g Setthe OUTPUT switch to OFF position Il h Connect the load to the Output terminals and set the OUTPUT switch to ON position NL LOAD CONNECTIONS The load should be connected to the power supply output terminals using separate pairs of connecting wires This will minimize mutual coupling effects between loads and will retain full advantage of the low output impedance of the power supply Each pair of connecting wires should be as short as possible and twisted or shielded to reduce noise pick up If a shielded pair is used connect one end of the shield to ground and leave the other end unconnected 5 44 4 5 Positive or negative voltage can be obtained from this supply by grounding ei2. N and rated Load Measure Vig across O P Ve and Capacitor Leaky Summing Capacitor C4 Ve Adjust that Vtg between 4 5V to 5V with Preset VR1 5K on V PREG PCB Replace It 1 Check whether Device Drop is between A DV to 5V It might not be proper 2 Leaky Summing Capacitor C4 on PREG PCB 23 J POOR LOAD REGULATION POOR LOAD REGULATION Load Terminal Nut inside Unit might be Loose N Is there any Oscillation in CV Mode N Is Capacitor C4 and C2 Leaky Y Y Reduce Resistor R6 2 2K on F Panel PCB until Oscillation dies OUT If Oscillation still Prevail reduce R9 to 2K on F Panel PCB Replace It 1 Load Terminal might be Loose Ensure Terminals are tightened properly with Terminal Nuts inside the Unit 2 There might be Oscillation at Output CV Mode Adjust Resistor R6 8 R9 until Oscillations die out 3 Check Capcitor C4 and C2 on PREG PCB It might be Leaky K CV CC LED NOT GLOW 1 Check the LED s it might be Leaky Open or Short 24 L EXTERNAL PROGRAMMING NOT OK EXTERNAL PROGRAMMING NOT OK Is Pot connected across INT Ensure 5K Pot connected amp COM OK between INT and COM Terminal Y Is there proper Continuity between PROG Terminal and O P Ve N Ensure proper Connectivity 1 Check whether 5K Pot is connected between INT and COM Terminal 2 Check whether there is proper Continuity between PROG Terminal and Output Positi
3. 11 5 3 6 II Fuse blows connect the unit through a variable AC Source with a current meter and monitor the current at no load If the current is very high more than 2 ampere or so load check for Bridge Rectifier short or shorted Diode or Secondary Winding short etc 5 3 7 II output voltage or current DPM s are not reading check for loose connections especially in crimping soldering of Connectors WARNING THE FOLLOWING SERVICING INSTRUCTIONS ARE FOR USE BY QUALIFIED PERSONNEL ONLY TO AVOID PERSONAL INJ URY DO NOT PERFORM ANY SERVICING OTHER THAN THAT CONTAINED IM OPERATING INSTRUCTIONS UNLESS YOU ARE QUALIFIED TO DO SO TO OPERATORS SAFETY SUMMARY AND SERVICE SAFETY SUMM 12 5 43 VOLTAGES AT VARIOUS PINS OF IC LM324 IS AS FOLLOWS IC 101 IC PIN NO VOLTAGES amp CHECK CONDITIONS PIN1 OV WHEN V POT KEPT AT MIN POSITION IN CV MODE PIN1 5V WHEN KEPT AT MAX POSITION IN CV MODE PIN2 amp 3 4 9V AT V POT MAX POSITION PIN4 12V ALL CONDITION PIN7 OV AT POT MIN POSITION PIN7 0 5V AT CC POT MAX POSITION PIN8 1V TO 3 5V IN CV PIN8 10V TO 11V IN CC MODE PIN9 CV PINTO 6LV PINTA 10 TO 11V IN CV MODE 5 44 A CHECK VOLTAGES AT D3 CATHODE 2V CV 10V CO CHECK VOLTAGES AT D4 CATHODE 10V CV 2V CC B C CHECK VOLTAGES AT 7101 CATHODE 4 7V D CHECK VOLTAGES AT 7102 CATHODE 10V 5 4 5 CHECK ALL REGULATORS OUTPUT WITH RESPECT TO
4. 1791 37 Service Information Warranty Service Please return the product in the original packaging with proof of purchase to the below address Clearly state in writing the perfor mance problem and return any leads connectors and accessories that you are using with the device Non Warranty Service Please return the product in the priginal packag ing to the below address Clearly state in writing the performance problem and return any leads connectors and accessories that you are using with the device Customers not on open account must include payment in the form of a money order or credit card For the most current repair charges contact the factory before shipping the product Return all merchandise to B amp K Precision Corp with pre paid shipping The flat rate repair charge includes return shipping to locations in North America For overnight shipments and non North America shipping fees contact B amp K Precision Corp 8 8 K PRECISION CORP 22820 Savi Ranch Parkway Yorba Linda CA 92887 Phone 714 921 9095 Fax 714 921 6422 Include with the instrument your complete return shipping address contact name phone number and description of problem amp PRECISION CORP Z 22820 Savi Ranch Parkway Yorba Linda CA 92887 M 00198 ad www bkprecision com
5. Is Current Pot Short Replace It N Is Wiring Related to N Ensure proper Continuity Current Pot OK Are Load Terminals connected properly with Nut inside Unit N Ensure proper Terminal Contact Check Current set Preset R21 It might be open No Contact of Load Terminals with the Terminal Nut inside the Unit Current Pot might be Shorted Check Wiring related to Current Pot 21 G UNIT DIRECTLY GOES TO CC UNIT DIRECTLY GOES TO CC Is Shunt Resistor open OR Dry Soldered N Is IC LM324 OK Y Replace Shunt Resistor if necessary Replace It Replace It Is Current select Preset R21 Open N Is Remote Sense Terminal Pressed Y Ensure Remote Sense Switch is Unpressed in Normal Condition Check the Shunt Resistor 0 025E 25E It might be Open or Dry Soldered Check IC LM 324 It might be Damaged Current select Preset R21 might be Open Remote Sense Terminal might be Pressed on No Load 22 NO CURRENT CONTROL NO CURRENT CONTROL Is Current Pot Open N Are Wires related to Current Pot OK Y Replace it Ensure proper Connectivity 1 Check the Current Potentiometer It might be Open 2 Check all Wires related to Current Potentiometer 1 POOR LINE REGULATION POOR LINE REGULATION Improper Device Drop Setting Keep the Input Supply at rated I P Keep the O P Supply at rated Vtg
6. J3 J2 54 5MSL 5 PIN SIL 2 54mm LOCK MALE J3 J2 54 5MSL 5 PIN SIL 2 54mm LOCK FEMALE 27 PS PREG 1791 0503 PCB ASSLY Reference Designation Reference Part Designator Description TRANSISTORS Q1 BC 109 Q4 Q2 MPSA12 Q5 Q3 BC 557 ZENERS 71 4 7V W Z2 PRESET VR1 3206F HOR TRANSFORMER T1 EE25 PULSE TX Z DPM 01 REV 01 X2 Reference Part Reference Designator Description Designation RESISTORS R1 39K 0 25W 596 MFR R6 R2 470K 0 25W 596 MER R7 R3 1M 0 25W 596 MFR R8 R4 SEL INPUT R9 R5 10K 0 25W 596 MFR PRESETS PR1 3K LIN VER REF ADJ CAPACITOR C1 220uF 50V EL C6 C2 0 1uF 100V MP C7 C3 0 01uF 100V MP C8 C4 0 1uF 100V MP C9 C5 0 1uF 100V MP C10 IC s IC1 7107 DECODER DRIVER VR1 TL 431 FND s V DPM 051 KLS 563G GREEN DS2 KLS 563G GREEN FND s A DPM DS1 KLS 563 I RED DS2 KLS 563 I RED LEDS LED1 3mm GREEN FOR CV LED2 3mm RED FOR A DPM MISCILLANEOUS J1 2 54 PITCH 3 PIN M J3 J2 Not Used 28 Part Description BC 557 BC 547 10 AW Part Description 2K4 0 25W 5 MFR 330K 0 25W 5 MFR 330K 0 25W 5 MFR 6K8K 0 25W 5 MFR 0 1uF 100V 10uF 50V ELE 50V CD 10uF 50V ELE 50V CD 053 KLS 563G GREEN 083 KLS 5631 RED 2 54 PITCH 4 PIN M PS AUX DC L1791 0503 PCB ASSLY Reference Part Reference Part Designator Description Designation Description CAPACITORS C1 470u
7. 5K Pot whether it is open or whether the wires associated with Voltage Potentiometer is reaching the Front Panel PCB Check the Mosfets and Zener Diodes across Mosfet It might be Short Check Diodes D3 and D4 on Front Panel PCB It might be Leaky or Short Ensure proper continuity of Gate Wire on Front Panel PCB and Mosfet module Ensure INT and COM Terminal at Back Panel are short when External Programming is not in use 17 C NO OUTPUT VOLTAGE NO O P VOLTAGE Is IC LM324 OK Y Replace It Replace It Replace It Replace It Ensure their proper Connectivity with PCB Is there proper contact of Load Ensure proper Connectivity Terminal with Terminal Nuts of Load Terminals and Inside Unit Terminal Nut inside Check IC LM324 on Front Panel PCB L1791 FP CNT 0603 It might be Damaged Check the voltage Potentiometer It might be Short Check Voltage Selection Preset R22 on Front Panel PCB It might be Open Check Preset VR1 on Pre regulator PCB PS PREG 1791 0503 It might be Open Check whether Auxillary Transformer Windings are reaching PCB Check whether there is proper contact between Load Terminals and Terminal Nuts inside the Unit 18 D NO DPM INDICATION NO DPM INDICATION Is Display Completely Blank N Is Continuity between IC7805 8 DPM OK N Does Display shows only Ensure proper Continuity dot Indication Y Is Continuit
8. CHASSIS ASSLY Reference Part Designator Description RESISTOR R1 4 7K 2W MOR R2 0 025E 25W SHUNT DIODES CR1 U30D40C 30AMP 400V DUAL DIODE CAPACITORS C1 6 X 15 000uF ELE C2 1uF 250V AC CAP X2 RECTIFIER HEATSINK ASSLY DIODES CR1 40HFR20 CR3 40HF20 CR2 40HFR20 CR4 40HF20 SCR1 2906 25A SCR1 2906 25A FILTER 15A 20A RFI FILTER VARISTOR 130V OR 230V TYPE 20D 361 FAN1 12V 24V INNOVATIVE HI COOL FAN2 12V 24V INNOVATIVE HI COOL 8 BACK TROUGH ASSLY Reference Part Designator Description FUSE1 20AMP TYPE F 115V 8 Amp TYPE T 230V 6 5mm X 32mm MAIN BOARD 3 PIN AMERICAN 12 AWG 3 CORE CABLE REMOTE TERMINAL 4 WAY 10A TERMINAL BLOCK 30 euluue yeg esues YOUMS esues speuiuue 109100 YOUMS 440 GL YOUMS 1eseJd uogeoipu L Nda lu uno CL SPO LL 8UIH 139202 1 0 V I TANVd LNOHd 1 09 juango Nda 104409 96 II0 V2IIM 40 NO 18MOd Q LO 31 NOILVIILNJA 9 GNNOHD JALLOJLOHd 7 QHOO SNIVAN 2 9 TVNINd31 I NVHOOud LX3 1NI 930 ICLI 504 LNdNI IL 1 0 V I TANVd MOVE dOL BOTTOM VIEW OF MODEL 1790 1791 34 FRONT PANEL CONTROL PCB OF 1790 1791 35 POWER MODULE PCB OF 1790 1791 36 PRE REGULATOR AUX P S PCBs 1790
9. during constant voltage operation Any capacitance added externally will improve the pulse current capability but will decrease the safety provided by the constant current circuit A high current pulse may damage load components before the average output current is large enough to cause the constant current circuit to operate The effects of the output capacitor during constant current operation are as follows a The output impedance of the power supply decreases with increasing frequency b The recovery time of the output voltage is longer for load resistance changes A large surge current causing a high power dissipation in the load occurs when the load resistance is reduced rapidly REVERSE VOLTAGE LOADING A diode CR1 is connected across the output terminals Under normal operation the diode is reverse biased anode connected to the negative terminal If a reverse voltage is applied to the output terminals positive voltage applied to the negative terminal the diode will conduct shunting current across the output terminals to the forward voltage drop of the diode This diode protects the series transistor and the output electrolytic capacitors REVERSE CURRENT LOADING Active loads connected to the power supply may actually deliver a reverse current to the power supply during a portion of its operating cycle An external source cannot be allowed to pump current into the supply without loss of regulation and possible damage t
10. not use an ohmmeter that has a high internal current High currents may damage a diode A diode may be checked for an open or shorted condition by measuring the resistantce With an ohmmeter scale having an internal source of between 800mV and 1 5V the resistance should be very high in one direction and very low when the leads are reversed 5 2 10 RESISTORS Checkthe resistors with an ohmmeter Resistor tolerances are given in the Electrical Parts List Resistors do not normally need to be replaced unless the measured value varies widely from the specified value 5 2 11 CAPACITORS A leaky or shorted capacitor can be detected by checking resistance with an ohmmeter on the voltage rating of the capacitor The resistance reading should be high after initial charge of the capacitor An open capacitor can best be detected with a capacito meter or by checking whether it passes ac signals 53 REPAIRS amp MAINTENANCE 5 3 1 Remove the mains cord from the source before removing top cover of the unit 5 3 2 To open the cover remove screws from Top amp Bottom Covers Disconnect Grounding of both covers 5 3 3 If there is no output check the input supply Voltage and the Fuse continuity etc Check both Fans are working 5 3 4 If the output is high and unregulated check for open Voltage adjust potentiometer or shorted mosfet etc 5 3 5 Similarly if the current is unregulated check for value change in the Shunt Resistor It may get open
11. that checks the simple trouble possibilities before proceeding to extensive troubleshooting 5 2 2 CONTROL SETTINGS Incorrect control settings can seem like a trouble that does not actually exist If there is any question about the correct function or operation of any control see the Operating Instructions section 5 2 3 SYSTEM AND ASSOCIATED EQUIPMENT Before trobleshooting the 1790 349 check for proper input fuse as per part list is intac Check the line voltage at the power source before connecting the mains cord is rated for the correct input voltage Verify that the front panel controls are kept at minimum position The output terminals must be free from any load connecting leads 5 2 4 VISUAL CHECK Many troubles can be located by visual clues such as unsoldered connections broken wires damaged circuit board damaged components etc 5 2 5 INTERNAL ADJUSTMENT Check the Adjustment of the suspected circuit if the trouble is obviously in a certain circuit The trouble may only be a result of misadjustment and may be corrected by readjustment 5 2 6 CIRCUIT ISOLATION Note the trouble symptoms These often identify the circuit in which the trouble is located When trouble symptoms appear in more than one circuit check the effected circuits by making waveform and voltage measurements 5 2 7 COMPONENT CHECKING If a component cannot be disconnected from its circuits then the effects of the associated circuitry must be considered wh
12. voltage and also reduces the amplitude of the feedback error signals that are developed within the unit Because of these factors it is recommended that the drop in each load lead does not exceed 0 5Volts NOTE Due to the voltage drop in load leads it may be necessary to readjust the current limit in the remote sensing mode Observance of the precautions in para 4 8 and 4 9 will result in a low dc output impedance at the load However another factor that must be considered is the inductance of long leads This causes a high ac impedance and could affect the stability of the feed back loop seriously enough to cause oscillations If this is the case it is recommended that the following actions be taken a Adjust R6 to remove oscillations or to achieve best possible transient response for given long load lead configuration b If performing adjustment in step a above does not remove oscillation disconn ect output capacitor C3 L1791 FP CNT 0603 PCB and connect a capacitor having similar characteristics approximately the same capaci tance the same voltage rating or greater and having good high frequency characteristics directly across load using short leads Readjust R6 as in step a above after making this change 6 4 6 4 7 4 8 4 9 OUTPUT CAPACITANCE Internal capacitor L1791 FP CNT 0603 PCB connected across the output terminals of the power supply helps to supply high current pulses of short duration
13. F 35V ELE C8 100nF 50V DISC C2 47uF 35V ELE C9 470LL 35V ELE C3 10uF 35V ELE C10 470uF 35V ELE C4 10uF 35V ELE C11 220uF 35V ELE C5 100nF 50V DISC C12 100nF 50V DISC C6 Not Used C13 100nF 50V DISC C7 Not Used C14 10uF 35V ELE ICs U1 LM 78T12 U3 LM 7805 U2 LM 7905 U4 LM 7812 BRIDGE BR1 WO06M 600V DIODES D1 1N4007 D4 1N4007 D2 1N4007 D5 Not Used D3 1N4007 D6 Not Used CONNECTORS J1 J2 54ST 10 10PIN SIL 2 54mm ST LOCK MALE J1 J2 54ST 10 10PIN SIL 2 54mm ST LOCK FEMALE J2 J2 54ST 12 12PIN SIL 2 54mm ST LOCK MALE J2 J2 54ST 12 12PIN SIL 2 54mm ST LOCK FEMALE PS PWR L1791 0703A PCB ASSLY Reference Part Reference Part Designator Description Designation Description RESISTORS R1 DIE 3W WWW R10 100K 0 25W 596 MFR R2 0 1E 3W WW R11 100K 0 25W 596 MFR R3 DIE WWW R12 100K 0 25W 596 MFR R4 DIE WWW R13 100E 0 25W 596 MFR R5 DIE WAN R14 100E 0 25W 596 MFR R6 DIE WWW R15 100E 0 25W 596 MFR R7 100K 0 25W 5 MFR 100E 0 25W 5 MFR 88 100K 0 25W 5 MFR 100E 0 25W 5 MFR R9 100K 0 25W 5 MFR 100E 0 25W 5 MFR ZENERS R1 12 12V W TRANSISTORS Q1 6 IRFP 150 MOSFET MISCELLANIOUS M7 8 M3 M4 CLICK NUT DQ1 3 ST MALE FASTNER 2 PIN SQ1 3 MOUNTING 29 6 FRONT PANEL ASSLY Reference Part Reference Part Designator Description Designation Description POT VR1 5K WWPOT VR3 500E WWPOT VR2 1K WWPOT VR4 50E WWPOT SWITCH SW1 16A 250V ON OFF SWITCH 7 MAIN
14. Instruction Manual Model 1794 High Current Power Supply Ce Limited Two Year Warranty B amp K Precision Corp warrants to the original purchaser that its product and the component parts therof will be free from defects in workmanship and materials for a period of two years from the data of purchase 8 amp K Precision Corp will without charge repair or replace at its option defective product or component parts Returned product must be accompanied by proof of the purchase date in the form a sales receipt To obtain warranty coverage in the U S A this product must be registered by completing and mailing the enclosed warranty card to B amp K Precision Corp 22820 Savi Ranch Parkway Yorba Linda CA 92887 within fifteen 15 days from proof of purchase Exclusions This warranty does not apply in the event of misuse or abuse of the product or as a result of unanthorized alternations or repairs It is void if the serial number is alternated fefaced or removed B amp K Precision Corp shall not be liable for any consequential damages including without limitation damages resulting from loss of use Some states do not allow limitation of incidental or consequential damages so the above limitation or execlusion may not apply to you This warranty gives you specific right and you may have other rights which vary from state to state Model Number Date Purchased TABLE OF CONTENTS SECTION PARTICULARS PAGE NO 1 GENERA
15. L INFORMATION 1 2 SPECIFICATIONS 2 3 INSTALLATION 3 4 OPERATING INSTRUCTIONS 5 5 SERVICE INSTRUCTIONS 10 6 PART LIST 16 7 SCHEMATICS 21 8 CIRCUIT DIAGRAMS 28 1 1 1 2 1 3 1 4 1 5 SECTION 1 GENERAL INFORMATION DESCRIPTION The 1794 High Current Regulated D C Power Supply is completely solid and suitable for bench operation or standard 19 rack operation It is a well regulated constant voltage constant current supply which delivers 0 32V at 0 20Amps and can be adjusted continuously throughout the output range When the supply is used constant voltage source the front panel VOLTAGE controls can be used to limit the output voltage When the unit is used as a constant current source the front panel CURRENT controls can be used to limit the output current The unit will automatically cross over from constant voltage to current mode and vice versa if the output current or voltage exceeds these limits Output voltage and current are continuously monitored on two front panel meters The load terminals and remote sense terminals are provided on the front panel Either the positive or negative output terminal may be grounded or the power supply can be operated floating at upto a maximum of 300VDC above ground OUTPUT ON OFF SWITCH The output voltage and Current can be preset without connecting the power supply to the load With the OUTPUT ON OFF switch in the OFF position the maximum voltage and current limits can
16. OUTPUT VE COMMON REF PCB NO PART NO PINNO VOLTAGES CHECK WITH RESPECT TO OUTPUT VE AS COMMON IC7812 12 0V All the above readings are approximate values The given voltages amp waveforms are refering to a normal working unit If find any Voltage or Waveform absent at given points then trace back to the associated circuits This complets basic trouble shooting test points 5 5 PARTS ORDERING amp REPLACING 5 5 1 OBTAINING REPLACEMENT PARTS Most electrical parts can be obtained through your local distributor or representative However you should be able to obtain many of the standard components from a local commercial source in 13 your area Before you purchase check the electrical parts list for the proper value rating tolerance and description 5 5 2 ORDERING PROCEDURE When ordering replacement parts from B K Inc please include the following minimum information 1 Power Supply Type 1794 2 Power Supply Serial Number For example 03080001 3 A description of the part if electrical include the circuit number 5 5 3 CIRCUIT BOARDS If a circuit board is damaged beyond repair the entire assembly including all soldered on components can be replaced To remove or replace a board proceed as follows 1 Disconnect all Sockets amp leads connected to the board both soldered lead connections and solderless pin connections 2 Remove all mounting screws holding the board in the i
17. be set Pressing the OUTPUT ON switch connects the output of the power supply to the load LIMIT SETTING The voltage and current limits can be set when the output is not connected to the load With the OUTPUT ON OFF switch in the OFF position and the LIMIT switch pressed the voltage and current limits can be set with the front panel VOLTAGE and CURRENT potentiometers REMOTE PROGRAMMING With External 5K Pot The output voltage of the unit can be programmed between 0 to 32V by means of an external remote programming voltage resistor An external resistance programming selector link is provided on the rear panel for this purpose REMOTE SENSING The degradation in regulation which occurs at the load due to voltage drop in the load leads can be eliminated by using the power supply in the remote sensing mode operation The remote sensing mode is selected by a push switch on the front panel OUTPUT VOLTAGE LOAD CURRENT CONSTANT VOLTAGE MODE REGULATION LINE LOAD RIPPLE amp NOISE CONSTANT CURRENT MODE REGULATION LINE LOAD RIPPLE amp NOISE OVERLOAD PROTECTION TRANSIENT RESPONSE STABILITY Total drift within 8 hours after warm up under constant line load amp temp PANEL METERS MODE INDICATION SET LIMIT ON OFF CONTROLS OUTPUT CONTROLS EXTERNAL PROGRAMMING OPERATING TEMPERATURE INPUT VOLTAGE DIMENSIONS WEIGHT SECTION 2 SPECIFICATIONS 0 32V DC continuously variable with coarse and fin
18. e voltage controls 0 30 Amp max continuously variable with coarse and fine controls Less than 0 01 2mV for 10 change in line voltage Less than 0 01 2mV for load change from zero to full load Less than 1mV rms max 20 Hz 20 MHz Less than 0 05 10mA for 10 change in line voltage Less than 0 05 10mA for change in output voltage from 0 volts to maximum output voltage Less than 6mA rms Automatic overload and short circuit protection 100usecs to within 10mV of set output voltage for load change from 10 to 90 0 2 10mV in constant voltage mode 0 5 10mA in constant current mode Digital panel meters marked V for voltmeter and A for ammeter are provided with an accuracy of 3 counts Respective LED lights up when the unit is working in CV or CC mode Push Switches for Limit V amp and output ON OFF setting Single turn coarse and fine voltage and current controls are provided on the front panel Output voltage can be programmed by a variable resistance of 5K Pot 0 400 120 230V AC 10 47 63Hz single phase 19 W x 15 75 D x 5 24 H 50 16 Net 2 EN 3 2 3 3 3 4 3 5 3 6 3 7 SECTION 3 INSTALLATION INITIAL INSPECTION As soon as the power supply 1794 unit is unpacked inspect for any damage that may have occurred during transit Save all packing material until inspection is completed If any damage is found notify the carriers immedia
19. en evaluating the measurement Except for soldered in transistors and integrated circuits most components can be lifted at one end from the circuit board 5 2 8 TRANSISTORS AND IC s the power switch off before removing replacing any semiconductor A good check of transistor operation is actual performance under operating conditions A transistor can most effectively be checked by substituting a new component for it or one which has been checked previously However be sure that circuit conditions are not such that a replacement transistor might also be damaged If substitute transistors are not available use a dynamic tester Static type testers are not recommended since they do not check operation under simulated operating conditions An approved anti static suction type desoldering tool must be used to remove soldered in transistors Integrated circuits can be checked with a voltmeter test oscilloscope or by direct substitution A good understanding of the theory of operation is essential to troubleshooting circuits using IC s Operating waveforms logic levels and other operating information for the IC s are given in the theory of operation Use care when checking voltages and waveforms around the IC s so that adjacent leads are not shorted together A convenient means of clipping a test probe to the 14 pin in line IC is with an integrated circuit test clip This device also doubles as an extraction tool 5 2 9 DIODES Do
20. ense Switch Pressed in Normal Condition N Is Device Drop setting proper on Load N Turn ON the Unit at Rated input Voltage Load the Unit at max rated Voltage and Current Adjust the Voltage between Output Positive and Capacitor Positive between 4 5V to 5V by using Please VR1 on PREG PCB 1 Check Line Voltage for 230V AC or 115V AC whichever applicable Check whether Fuse Present is 20A for 115V and 10A for 230VAC Check the Transformer Tapping whether it is configured accordingly to Line Voltage 4 The Power Diodes connected in Bridge configuration on Heat sink might be short 5 I Remote Sense Switch is pressed on Load in Normal Operation there is chance unit may take High Current and Fuse might Blow 6 If Device Drop measured across O P Positive and Capacitor Positive is not between 4 5V to 5V at rated I P Voltage and rated O P Voltage and Load condition there is a chance of Fuse getting blow in Load Condition Note 4 5V to 5V Device Drop at Full Load 16 8 UNREGULATED O P VOLTAGE Is IC LM324 OK N Replace the IC Replace the Voltage Pot and Ensure proper continuity with the PCB Replace the Damaged Mosfet Ensure proper continuity of Gate Wire and PCB Replace the Damaged Diode Short INT COM Terminal when External Programming is not in use Check IC LM324 on Front Panel PCB L1791 FP CNT0603 It might be damaged Check Voltage Potentiometer
21. ischarge Static voltages of 1KV to 30KV are common in unprotected environments Observe the following precautions to avoid damage Minimize handling of static sensitive components Transport and store static sensitive components or assemblies in their original containers ona metal rail or on conductive foam Label any packages that contains static sensitive assemblies or components Discharge the static voltages from your body by wearing a wrist strap while han dling these components Servicing static sensitive assemblies or components should be performed only at a static free workstation by qualified service personnel Nothing capable of generating or holding a static charge should be allowed on the work station surface Keep the component leads shorted together whenever possible Pick up components by the body never by the leads Do not slide the components over any surface Avoid handling components in areas that have a floor or work surface covering capable of generating a static charge Use a soldering iron that is connected to earth ground Use only special anti static suction type or wick type desoldering tools 15 FAULT FINDING PROCEDURE A FUSE BLOWS FUSE BLOWS Is Line Voltage OK Y Adjust Proper Line Voltage Insert proper rating Fuse Adjsut the Tap according to required voltage Replace the Damaged Diodes Release the Remote Switch in Normal Load Condition Is Remote S
22. ltage should not be more than 250V rms A protec tive ground connections by way of the grounding conductor in the power cord is essential for safe operation GROUNDING THE PRODUCT This product is grounded through the grounding conductor of the power cord To avoid electrical shock plug the power cord into a properly wired receptacle before connecting to the product input or output terminals A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation DANGER ARISING FROM LOSS OF GROUND Upon loss of the protective ground connection all accessible conductive parts including knobs and controls that may appear to be insulating can render an electric shock USE THE PROPER POWER CORD Use only the power cord and connector specified for your product Use only a power cord that is in good condition Refer cord and connector changes to qualified service personnel 8 USE THE PROPER FUSE To avoid fire hazard use only fuse of the correct type voltage rating and current rating as specified in the parts list for your product For 115V operation 20A For 230V operation 10A Slow blow Refer fuse replacement to qualified service personnel DO NOT OPERATE IN EXPLOSIVE ATMOSPHERES To avoid explosion do not operate this instrument in an explosive atmosphere unless it has been specifically certified for such operation DO NOT OPERATE UNIT WITHOUT COVERS avoid personal injury do no
23. mp Auxilary Transformer as per the following diagram TAP SELECTOR BOARD Please make sure the input varistor is replaced by 20D 361K or equivalent for 230V Mains Operation at the Input of EMI Filter located at bottom side of the unit 3 9 REPACKAGING FOR SHIPMENT To ensure safe shipment of the power supply 1794 unit it is recommended that the package designed for the unit be used The original packaging material is reusable Be sure to attach a tag to the unit specifying the owner and the fault observed with a brief description 4 1 4 2 4 3 SECTION 4 OPERATING INSTRUCTIONS TURN ON SETTING PROCEDURE The following procedure describes the use of controls and indicators for Constant Voltage and Constant Current Mode of Operation CONSTANT VOLTAGE CV MODE a Set POWER ON Switch amp keep the OUTPUT ON OFF switch to OFF position Bl b Press LIMIT switch and adjust the VOLTAGE controls till the desired voltage is indicated on Voltmeter c Press OUTPUT switch to ON position and observe that CV LED lights CONSTANT CURRENT VOLTAGE CC MODE a Turnoff the suppy Short circuit the output terminals of the power supply amp turn on the supply b Keep the OUTPUT ON OFF switch in the OFF position MEL c Press LIMIT switch and adjust the CURRENT controls till the desired current is indicated on Ammeter IL d Press OUTPUT switch ON position and observe that CC LED lights
24. nstrument Remove any knobs etc that would prevent the board from being lifted out of the instrument 3 Lift the circuit board out of the unit Do not force or bend the board 4 To replace the board reverse the order of removal Use care when replacing pin connectors If forced into place incorrectly positioned the pin connectors may be damaged 5 5 4 TRANSISTORS AND IC s Transistors and IC s should not be replaced unless they are actually defective If removed from their sockets during routing maintenance return them to their original sockets Unnecessary replacement or switching of semiconductor devices may affect the calibration of the instruments When a transistor is replaced check the operation of the part of the instrument that may be affected Replacement semiconductors should be of the original type ora direct replacement When removing soldered in transistors use an approved anti static suction type desoldering tool to remove the solder from the holes in the circuit board An extracting tool should be used to remove the 14 pin integrated circuits to pre vent damage to the pins If an extracting the pins Pull slowly and evenly on both ends of the IC Avoid having one end of the IC disengage from the socket before the other end 14 10 CAUTION Static discharge can damage any semiconductor component in this instrument This instrument contains electrical components that are susceptible to damage from static d
25. o the output capacitor To avoid these effects it is necessary to preload the supply with a dummy load resistor so that the power supply delivers current through the entire operation cycle of the load device EXTERNAL PROGRAMMING Remote external programming can be achieved changing the external program link on rear panel and connecting a variable resistor of 5K across the terminals as shown on the rear panel OPERATORS SAFETY SUMMARY The general safety information in this part of the summary is for both operating amp servicing personnel Specific warnings and cautions will be found throughout the manual where they apply but may not appear in this summary TERMS IN THIS MANUAL CAUTION Statements identify conditions or practices that could result in damage to the equipment or other property WARNING Statements identify conditions or practices that could result in personal injury or loss of life TERMS AS MARKED ON EQUIPMENT CAUTION Indicates a personal injury hazards not immediately accessible as one reads the markings or a hazard to property including the equipment itself DANGER Indicates a personal injury hazard immediately accessible as one reads the marking POWER SOURCE This product is intended to operate from a power source that does not apply more than 130V rms between the suply conductors or between either supply conductor and ground Ifthe Internal Tap is selected for 230VAC operation then the input vo
26. signation Description CONNECTORS J1 J2 54 3MSL 3 PIN SIL 2 54mm ST LOCK MALE J1 J2 54 3FSL 3 SIL 2 54mm ST LOCK FEMALE CLAMPS SW1 SINGLE PUSH SWITCH MTG CLAMP SW2 DOUBLE PUSH SWITCH MTG CLAMP SW3 DOUBLE PUSH SWITCH MTG CLAMP SWITCHES Swi GREY COLOUR CAP FOR PUSH SWITCH SW2 GREY COLOUR CAP FOR PUSH SWITCH SW3 GREY COLOUR CAP FOR PUSH SWITCH 2 PS PREG 1791 0503 PCB ASSLY Reference Part Reference Part Designator Description Designation Description RESISTORS R1 3K3 2W MOR R15 100K 0 25W 5 MER R2 270E 2W MOR R16 39K 0 25W 596 MFR R3 324 0 25W 5 MER R17 10K 0 25W 5 MFR R4 82K 0 25W 5 MFR R18 10K 0 25W 5 MFR R5 10K 0 25W 5 MER R19 3K9 0 25W 5 MFR R6 180K 0 25W 5 MFR R20 390E 0 25W 5 MFR R7 8K2 0 25W 5 MFR R21 1K5 0 25W 5 MFR R8 330K 0 25W 5 MFR R22 4 7E 0 25W 5 MFR R9 180K 0 25W 5 MFR R23 3K9 0 25W 5 MFR R10 4K7 0 25W 5 MFR R24 15E 0 25W 5 MFR R11 820E 0 25W 5 MFR R25 10E 0 25W 5 MFR R12 6K8 0 25W 5 MFR R26 10E 0 25W 5 MFR R13 12K 0 25W 5 MFR R27 270E 2W MOR R14 10K 0 25W 5 MFR CAPACITOR C1 33pF 50V ELE C5 0 1uF 63V C2 4 7uF 50V ELE C6 470uF 50V ELE C3 2 2uF 50V ELE C7 0 1uF 230V AC C4 63V ELE DIODES D1 22 1N4007 200V 1A CONNECTORS J1 J2 54 6MSL 6 PIN SIL 2 54mm LOCK MALE J1 J2 54 6MSL 6 PIN SIL 2 54mm LOCK FEMALE J2 J2 54 4MSL 4 PIN SIL 2 54mm LOCK MALE J2 J2 54 4MSL 4 PIN SIL 2 54mm LOCK FEMALE
27. t operate this product without covers or panels installed SERVICING SAFETY SUMMARY FOR QUALIFIED SERVICE PERSONNEL ONLY Refer also to the Operators Safety Summary DO NOT SERVICE ALONE Do not perform internal service or adjustment of this product unless another person capable of rendering first aid and resuscitation if present USE CARE WHEN SERVICING WITH POWER ON Dangerous voltages exist at several points in this product To avoid personal injury do not touch exposed connections or components while power is on Disconnect power before removing protective panels soldering or replacing components POWER SOURCE This product is intended to operate from a power source that does not apply more than 130V rms between the supply conductors or between either supply conductor and ground A protective ground connection by way of the grounding connector in the power cord is essential for safe operation SECTION 5 SERVICE INSTRUCTION 5 1 GENERAL The instrument has been tested throughly and then released for dispatch Normally the unit works satisfactorily under all condition However due to ageing misuse or malfunctioning the unit may become defective In case the user wants to carryout Servicing the following instructions will be helpful in rectifying the defects The Servicing shall be done only by Qualified personnel 5 2 TROUBLE SHOOTING TECHNIQUES 5 2 1 INTRODUCTION The trouble shooting procedure is arranged in an order
28. tely Our authorised representatives should also be notified PHYSICAL CHECK This check should confirm that there are no broken knobs or connectors that the cabinet and panel surfaces are free of dents and scratches and the meters are not scratched and cracked ELECTRICAL CHECK The power supply unit 1794 should be checked against electrical specifications An in cabinet performance check will verify proper operation INSTALLATION DATA The power supply unit 1794 is shipped ready for bench operation It is necessary only to connect the unit to a rated source of power 120V AC and it is ready for operation LOCATION The power supply 1794 unit is fan cooled Sufficient space should be kept around the unit while in operation so that unit do not remain in confined space or close to another heating source The ambient temperature of the area around the unit should be less than 40 RACK MOUNTING The unit is in rack size and can be rack mounted in a conventional rack using standard mounting screws and the rack attachments optionally supplied INPUT POWER REQUIREMENTS The power supply 1794 unit may be operated continuously from input voltage of 120V or 230V AC 47 63Hz power source It is factory wired for 120V AC operation 38 INPUT TAP SELECTION FOR 230V OPERATION In case of 230V Mains operation please ensure that shorting links on the Tap Selector board is changed to 230V marked on the PCB for both Mains Transformer a
29. ther one of the output terminals or one end of the load Always use two leads to connect load to the supply regardless of where the setup is grounded This will eliminate any possibility of the output current return paths through the power source ground which would damage the line cord plug This supply can also be operated upto 300V DC above ground if neither output terminal is grounded REMOTE SENSING Warning Do not Operate the Unit in REMOTE SENSE mode without ensuring proper REMOTE 4 TERMINAL Connections Serious Damage to Unit or Equipment under test could result Remote sensing is used to maintain good regulation at the load and reduce the degradation of regulation which could occur due to the voltage drop in the leads betweeen the power supply and the load Remote sensing is accomplished by connnecting the load to remote sense terminals on the front panel The leads from the sensing S and S terminals to the load will carry much less current than the load leads and it is not required that these leads be as heavy as the load leads However they must be twisted or shielded to minimize noise pickup For reasonable lengths of load leads remote sensing greatly improves the performance of the supply However if the load is located at a considerable distance from the supply added precautions must be observed to obtain satisfactory operation Notice that the voltage in the load leads subtracts directly from the available output
30. ve M REMOTE SENSE NOT OK 1 Check whether there are Oscillations at Output when Remote Sense Switch is pressed If Oscillations are present reduce Resistor 86 and R9 on Front Panel PCB until Oscillations die out 25 SECTION 6 PART LIST amp SCHEMATICS L1791 FP CNT 0603 PCB ASSY Reference Part Reference Part Designator Description Designation Description RESISTORS R1 1K R22 500E 3206F R2 Not Used R23 33K R3 100E R24 10K R4 3 3K R25 10K R5 1K R26 100E 3206F R6 2 2K R27 Not Used R7 4K7 R28 100E 3206F R8 6K8 R29 1K R9 6K8 R30 560E R10 15K R31 820E R11 1K R32 100E 3206F R12 1K R33 Not Used R13 1K 10W R34 100K R14 1K R35 Short R15 1K R36 1 5K R16 3 3E R37 Short R17 100E R38 330K R18 2 2 839 100C R19 2K R40 1K8 R20 3K6 R41 12K R21 500E 3206F ZENERS 71 IL 431 72 IL 431 DIODES D1 1N4148 D4 1N4148 D2 1N4148 D5 1N4007 D3 1N4148 D6 1N4007 CAPACITORS C1 1KPF 100V DISC C5 10uF 35V ELE C2 1uF 100V ELE C6 10uF 35V ELE C3 220uF 50V ELE C7 Not Used C4 1KPF 100V DISC C8 0 1uF 230V IC U1 LM324 SWITCHES SW1 3 2P2W SW PUSH BUTTON TERMINALS I1 60 1000V Ve RED TERMINAL 4mm T2 60 1000V OP Ve LIGHT BLUE TERMINAL 4mm T3 10A 1000V Sns Ve RED BANANA TERMINAL 25mm L T4 10A 1000V Sns Ve BLACK BANANA TERMINAL 25mm L T5 EARTH BRASS BINDING NICKEL PLATED 4mm 26 1 L1791 FP CNT 0603 PCB ASSY eference ar eference ar Designator Description De
31. y between IC7905 amp Ensure proper Continuity DPM s OK Y Is Continuity between ANGD amp DPM s OK Ensure proper Continuity Y Is DPM IC OK N Replace It If there is no Indication at all ensure that there is proper Continuity between 5V Wire of DPM s and IC7805 It might be possible that 5V Wire Crimping might be loose or 1 7805 might be Damaged It DPM shows only a Dot Indication Check whether 5V from IC 7905 is reaching DPM s It might be possible that 5V Wire Crimping might be loose or IC 7905 might be Damaged If DPM shows Dot Indication check whether AGND Grey Wire is reaching DPM s If DPM shows Dot Indication check DPM IC7107 It might be Damaged E DPM NOT READ 000 DPM NOT READ V amp I 000 Is DPM IC 707 OK Y Does Hi and Low Wire Reach DPM s Y IC TL431 OK Y Is minimum Resistance of Pot High Y Replace It Ensure proper Continuity Replace It Replace Pot Check whether Voltage Hi and Voltage Low Wire is reaching DPM Check DPM IC 7107 It might be Damaged Check minimum Output Voltage of Potemtiometer It should be less than 150mV See that Power Supply is earthed properly Check IC TL 431 Z1 and Z2 on Front Panel PCB It might be Damaged If Current DPM does not read then check whether Current Hi and Low Wire is reaching Current DPM 20 F UNIT NOT TAKE CURRENT UNIT NOT TAKE CURRENT Is Current Set Preset R21 OK Replace It Y
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