BK Precision 1794, Instruction Manual

Page 1: ...Instruction Manual Model 1794 High Current Power Supply B PRECISION K ...

Page 2: ...rranty card to B 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 K Precision Corp shall not be liable for any consequential damage...

Page 3: ... OF CONTENTS SECTION PARTICULARS PAGE NO 1 GENERAL 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 ...

Page 4: ...can be operated floating at upto a maximum of 300VDC above ground 1 2 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 be set Pressing the OUTPUT ON switch connects the output of the power supply to the load 1 3 LIMIT SETTING The voltage and ...

Page 5: ...tection TRANSIENT RESPONSE 100µsecs to within 10mV of set output voltage for load change from 10 to 90 STABILITY Total drift within 8 hours after 0 2 10mV in constant voltage mode warm up under constant line 0 5 10mA in constant current mode load temp PANEL METERS Digital panel meters marked V for voltmeter and A for ammeter are provided with an accuracy of 3 counts MODE INDICATION Respective LED ...

Page 6: ...eck will verify proper operation 3 4 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 3 5 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 ...

Page 7: ...OARD 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 specif...

Page 8: ...ws a Set the OUTPUT switch to OFF position Release Position b Press the LIMIT switch and adjust the desired output voltage with the VOLTAGE control potentiometers c Release the LIMIT switch set the OUTPUT switch to ON position and check the output voltage on the voltmeter d Set the OUTPUT switch to OFF position e Press the LIMIT switch and adjust the desired output current limit with the CURRENT c...

Page 9: ...rformance 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 voltage and also reduces the amplitude of the feedback error signals that are developed within the unit Because of these factors it is recommended ...

Page 10: ...ed 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 elect...

Page 11: ...ms between the suply conductors or between either supply conductor and ground If the Internal Tap is selected for 230V AC operation then the input voltage 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 cor...

Page 12: ...ED 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 componen...

Page 13: ...nput 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 ...

Page 14: ... 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 Check the resistors with an ohmmeter Resistor tolerances are given in the Electrical Parts List Resistors do not normally n...

Page 15: ...ry Winding short etc 5 3 7 If 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 INJURY DO NOT PERFORM ANY SERVICING OTHER THAN THAT CONTAINED IN OPERATING INSTRUCTIONS UNLESS YOU ARE QUALIFIED TO DO SO REFER TO OPERATORS SAF...

Page 16: ...CK VOLTAGES AT Z102 CATHODE 10V 5 4 5 CHECK ALL REGULATORS OUTPUT WITH RESPECT TO OUTPUT VE COMMON REF PCB NO PART NO PIN NO VOLTAGES U1 IC7812 3 12V U2 IC79L05 3 5 0V U3 IC7805 3 5 0V CHECK WITH RESPECT TO OUTPUT VE AS COMMON U4 IC7812 3 12 0V All the above readings are approximate values The given voltages waveforms are refering to a normal working unit If find any Voltage or Waveform absent at ...

Page 17: ... 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...

Page 18: ...3 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 4 Nothing capable of generating or holding a static charge should be allowed on the work station surface 5 Keep the component leads shorted together whenever ...

Page 19: ...ositive between 4 5V to 5V by using Please VR1 on PREG PCB 1 Check Line Voltage for 230V AC or 115V AC whichever applicable 2 Check whether Fuse Present is 20A for 115V AC I P and 10A for 230VAC I P 3 Check the Transformer Tapping whether it is configured accordingly to I P Line Voltage 4 The Power Diodes connected in Bridge configuration on Heat sink might be short 5 If Remote Sense Switch is pre...

Page 20: ...Short Short INT COM Terminal when External Programming is not in use 1 Check IC LM324 on Front Panel PCB L1791 FP CNT0603 It might be damaged 2 Check Voltage Potentiometer 5K Pot whether it is open or whether the wires associated with Voltage Potentiometer is reaching the Front Panel PCB 3 Check the Mosfets and Zener Diodes across Mosfet It might be Short 4 Check Diodes D3 and D4 on Front Panel PC...

Page 21: ... Terminal with Terminal Nuts of Load Terminals and Inside Unit Terminal Nut inside 1 Check IC LM324 on Front Panel PCB L1791 FP CNT 0603 It might be Damaged 2 Check the voltage Potentiometer It might be Short 3 Check Voltage Selection Preset R22 on Front Panel PCB It might be Open 4 Check Preset VR1 on Pre regulator PCB PS PREG 1791 0503 It might be Open 5 Check whether Auxillary Transformer Windi...

Page 22: ...ere 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 IC7805 might be Damaged 2 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 3 If DPM shows Dot Indication check wheth...

Page 23: ...eck whether Voltage Hi and Voltage Low Wire is reaching DPM 2 Check DPM IC 7107 It might be Damaged 3 Check minimum Output Voltage of Potemtiometer It should be less than 150mV 4 See that Power Supply is earthed properly 5 Check IC TL 431 Z1 and Z2 on Front Panel PCB It might be Damaged 6 If Current DPM does not read then check whether Current Hi and Low Wire is reaching Current DPM Y Y Y Y N N N ...

Page 24: ...d to Ensure proper Continuity Current Pot OK Are Load Terminals connected properly with Nut inside Unit Ensure proper Terminal Contact 1 Check Current set Preset R21 It might be open 2 No Contact of Load Terminals with the Terminal Nut inside the Unit 3 Current Pot might be Shorted 6 Check Wiring related to Current Pot N Y N Y N Y N 21 ...

Page 25: ...s Current select Preset Replace It R21 Open Is Remote Sense Terminal Pressed Ensure Remote Sense Switch is Unpressed in Normal Condition 1 Check the Shunt Resistor 0 025E 25E It might be Open or Dry Soldered 2 Check IC LM 324 It might be Damaged 3 Current select Preset R21 might be Open 6 Remote Sense Terminal might be Pressed on No Load Y N Y N Y N Y 22 ...

Page 26: ...ter Y N Y I 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 and rated Load Measure Vtg across O P Ve and Capacitor Leaky Summing Capacitor C4 Ve Adjust that Vtg between 4 5V to 5V with Preset VR1 5K on PREG PCB Replace It 1 Check whether Device Drop is between 4 5V to 5V It might not be proper 2 Leaky Summin...

Page 27: ...ail reduce R9 to 2K on F Panel PCB Is Capacitor C4 and C2 Leaky 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 in CV Mode Adjust Resistor R6 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 o...

Page 28: ... O P Ve 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 Positive 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 R6 and R9 on Front Panel PCB until Oscillations die out N N Y 25...

Page 29: ...R36 1 5K R16 3 3E R37 Short R17 100E R38 330K R18 2K2 R39 100E R19 2K R40 1K8 R20 3K6 R41 12K R21 500E 3206F ZENERS Z1 TL 431 Z2 TL 431 DIODES D1 1N4148 D4 1N4148 D2 1N4148 D5 1N4007 D3 1N4148 D6 1N4007 CAPACITORS C1 1KPF 100V DISC C5 10µF 35V ELE C2 1µF 100V ELE C6 10µF 35V ELE C3 220µF 50V ELE C7 Not Used C4 1KPF 100V DISC C8 0 1µF 230V IC U1 LM324 SWITCHES SW1 3 2P2W SW PUSH BUTTON TERMINALS T1...

Page 30: ...K 0 25W 5 MFR R4 82K 0 25W 5 MFR R18 10K 0 25W 5 MFR R5 10K 0 25W 5 MFR 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 27...

Page 31: ...330K 0 25W 5 MFR R3 1M 0 25W 5 MFR R8 330K 0 25W 5 MFR R4 SEL INPUT R9 6K8K 0 25W 5 MFR R5 10K 0 25W 5 MFR PRESETS PR1 3K LIN VER REF ADJ CAPACITOR C1 220µF 50V EL C6 0 1µF 100V MP C2 0 1µF 100V MP C7 10µF 50V ELE C3 0 01µF 100V MP C8 0 1µF 50V CD C4 0 1µF 100V MP C9 10µF 50V ELE C5 0 1µF 100V MP C10 0 1µF 50V CD IC s IC1 7107 DECODER DRIVER VR1 TL 431 FND s V DPM DS1 KLS 563G GREEN DS3 KLS 563G G...

Page 32: ... 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 5 PS PWR L1791 0703A PCB ASSLY Reference Part Reference Part Designator Description Designation Description RESISTORS R1 0 1E 3W W W R10 100K 0 25W 5 MFR R2 0 1E 3W W W R11 100K 0 25W 5 MFR R3 0 1E 3W W W R12 100K 0 25W 5 MFR R4 0 1E 3W W W R1...

Page 33: ...C 30AMP 400V DUAL DIODE CAPACITORS C1 6 X 15 000µF ELE C2 1µF 250V AC CAP X 2 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 TYP...

Page 34: ...Voltage Coarse Control 7 CV Mode INdication 12 Output Terminals 3 Voltage Fine Control 8 Current DPM 13 Remote Sense Switch 4 Voltage DPM 9 CC Mode Indication 14 Remote Sense Terminal 5 Current Coarse Control 10 Output Preset Switch 15 Earth Terminal FRONT PANEL LAYOUT 31 ...

Page 35: ...1 INPUT FUSE HOLDER 3 INT EXT PROGRAM TERMINAL 5 COOLING FAN 2 MAINS CORD 4 PROTECTIVE GROUND 6 VENTILATION BACK PANEL LAYOUT 32 ...

Page 36: ...TOP VIEW 33 ...

Page 37: ...BOTTOM VIEW OF MODEL 1790 1791 34 ...

Page 38: ...FRONT PANEL CONTROL PCB OF 1790 1791 35 ...

Page 39: ...POWER MODULE PCB OF 1790 1791 36 ...

Page 40: ...PRE REGULATOR AUX P S PCBs 1790 1791 37 ...

Page 41: ...ou 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 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 Ame...

Page 42: ...SN 480 808 9 001 Printed in India M 00198 B K PRECISION CORP 22820 Savi Ranch Parkway Yorba Linda CA 92887 www bkprecision com B PRECISION K ...