
Models 1620A/ 1621A/ 1622A/ 
1623A/ 1626A/ 1627A 
DC REGULATED 
POWER SUPPLY 
 

TABLE OF CONTENTS 
7. MAINTENANCE ........................................................................13 
 7.1 Main fuse replacement .............................................................13  
 7.2 Calibrations ..............................................................................13  
 7.3 Voltage calibration ...................................................................14 
 7.4 Voltmeter alignment ................................................................14 
 7.5 Current calibration ...................................................................14 
 7.6 Ammeter alignment ..................................................................14 
LIMITED WARRANTY ................................................................15 
SERVICE INFORMATION ..........................................................16 
1. INTRODUCTION ........................................................................ 3 
2. FEATURES .................................................................................. 3 
3. SPECIFICATIONS ...................................................................... 4 
4. PRCAUTIONS FOR USE ........................................................... 6 
 4.1 Confirming the supply range ..................................................... 6 
 4.2 Precautions for connection of output terminals ......................... 6 
 4.3 Operating environment .............................................................. 7 
5. EXPLANATION OF PANEL...................................................... 7 
 5.1 FRONT PANEL ........................................................................ 7 
 5.2 REAR PANEL .......................................................................... 9 
6. OPERATION PROCEDURES ................................................. 10 
 6.1 Stand-alone operation .............................................................. 10  
 6.2 Serial connection ..................................................................... 10 
 6.3 Parallel operation (MASTER / SLAVE Control) .................... 11 
 

1. INTRODUCTION 
  The BK Precision Analog and Digital series are high quality 
serial control type DC Regulated Power Supplies. These models 
can be operated at constant voltage or constant current mode 
whose output can be varied from 0 up to the rated values for 
respective model. 
  It is a compact unit provided with separate voltage and 
current meters (Analog for 1620A, 1622A, 1626A and 3-digit 
LEDS for 1621A, 1623A, and 1627A series) for monitoring the 
output voltage and current simultaneously. In terms of 
operability, these units enable high precision, continuous 
variability via coarse and fine adjust knobs. The BK Precision 
Analog and Digital series can be connected in parallel with 
multiple units of the same model set up a “master/slave” 
configuration to increase the output current capability. Serial 
connection of multiple units can be used to increase the output 
voltage level. 
  This family of power supplies provides clean and stable DC 
output which is most suitable for many areas including 
laboratory, industrial, field service, hobby, and telecommucation 
applications. 
2. FEATURES 
• The BK Precision Analog and Digital series are constant 
voltage / constant current power supplies which feature 
excellent line and load regulations, low ripple and noise 
characteristics. 
• The units feature separate voltage and current meters so 
that output voltage and current can be monitored 
simultaneously. 
• Output voltage and current can be adjusted continuously 
in full range to any desired values. Adjustment can be 
done easily and precisely by using separate coarse and 
fine adjust knobs. 
• The constant current circuit operates to protect against 
overload and output short circuit. The limiting current 
values can be preset in the full range of the rated values 
for respective model. 
• Multiple units of power supplies of same family can be 
connected in series to provide higher output voltage. 
• Multiple units of power supplies of SAME model can be  
connected in parallel (master / slave configuration) to 
achieve higher output current. 
 

3. SPECIFICATIONS 
CONSTANT VOLTAGE CHARACTERISTICS 
Line regulation  
(120VAC + 10 %, -6 % ) 
CONSTANT CURRENT CHARACTERISTICS 
Line regulation 
(120VAC + 10 %, -6 % ) 
Output terminals ( color ) 
( + ) Red , ( – ) Black , ( GND ) Green 
 

Serial connection  
( independent control mode ) 
Can be connected in series ( within limits of ground proof voltage ) 
Parallel operation 
( master – slave mode ) 
Can be operated in “one-control” parallel configuration ( only same model ) 
VA / W 
( for rated load of AC 220V ) 
120V AC ± 10%, 60 Hz (120/220/230/240V AC ± 10%, 50/60Hz version available) 
Operating ambient temperature 
NOTE: Specifications and information are subject to change without notice. Please visit www.bkprecision.com for the most current product information. 
 

4. PRECAUTIONS FOR USE 
 4.1 . CONFIRMING THE SUPPLY RANGE 
The unit must be used within its specified range. The rated input 
voltage can be found on the rating table under the unit. Before 
plugging into the AC supply outlet, check if the input rating conforms 
to your local supply. For certain models, a voltage selector is 
available, switch the voltage selector to the correct position before 
use. Also, please check that you have the correct fuse inserted in the 
fuse box below the AC input receptacle. 
4.2. PRECAUTIONS FOR CONNECTION OF 
OUTPUT TERMINALS 
These units are a floating type power supply. For ordinary use, be 
sure that the MASTER/SLAVE switch on the rear panel is set to 
MASTER position and either the (+) output terminal or the (−)  
terminal is connected to the GND terminal (chassis GND) via the 
shorting bar. 
Warning: For model 1622A and 1623A, the maximum output 
voltage is up to 60Vdc. Touching the live metal part of output terminals 
may be hazardous. User must avoid touching the live metal part of output 
    4.3. OPERATING ENVIROMENT 
  Be sure to use this unit within the specified ambient 
temperature range listed in the specification table. 
  Because the unit is cooled by natural convection, do 
not place objects on top to block the convection. Also 
user must avoid placing the unit on or near any heat 
emitting devices or use multiple units in stacked 
configuration. For best results, use the unit in an 
environment that has good cross-ventilation. 
  Altitude up to 2000M  
  Installation category: CAT II  
  Pollution degree: 2  
  Indoor use only 
 

1. Power switch 
  Turns the power supply ON-OFF. The switch will be 
lighted up when the unit is ON. 
2. DC Voltmeter 
  Indicates the present output voltage. (Analog for 
162A, 1622A, 1626A and 3-digit LEDS for 1621A, 
1623A, and 1627A series) 
3. DC Ammeter 
Indicates the present output current. (Analog for 
162A, 1622A, 1626A and 3-digit LEDS for 1621A, 
1623A, and 1627A series) 
4. Constant current mode (C.C.) indicator 
  Indicates the power supply is operating in constant 
current mode. 
5. Constant voltage mode (C.V.) indicator 
  Indicates the power supply is operating in constant 
voltage mode. 
6. Voltage coarse adjust 
  Coarse adjust knob for the output voltage in voltage 
mode. 
7. Voltage fine adjust 
  Fine adjust knob for the output voltage in voltage mode. 
8. Current coarse adjust 
  Coarse adjust knob for current limiting point and current 
value in constant current mode. 
9. Current fine adjust 
  Fine adjust knob for current limiting point and current 
value in constant current mode. 
10. Output terminal positive (+) 
  Terminal for tapping of positive (+) output. 
11. Output terminal negative (–) 
  Terminal for tapping of negative (–) output. 
12. Ground terminal (GND) 
  Chassis ground terminal. Normally, this is connected to 
either (+) or (–) terminal depend on application. 
 

13. Master / Slave switch 
  Used during “master / slave control” parallel operation in 
MASTER / SLAVE configuration. For normal operation,  
switch should be set to MASTER. 
14. In / out terminals for Master / Slave operation 
  Control terminals for use in the “MASTER / SLAVE control” 
parallel operation mode. 
15. Heat sink 
  Heat sink for the power supply. Be careful as this area can 
become quite hot during operation. 
16. Main Fuse 
17. Power cable 
5.2  REAR 
 

6. OPERATION PROCEDURES 
6.1 . STAND-ALONE OPERATION 
When using the power supply in stand-alone mode, simply 
operate by manipulation of the panel switches and 
adjustment knobs as needed. 
However, be sure that MASTER / SLAVE switch is set to 
MASTER position. 
6.2.  SERIAL CONNECTION 
Two or more units of the power supply can be hooked up in 
series to achieve higher output voltage. The resulted output 
will be sum of the outputs of the individual units. In this 
situation, however, care must be taken that the voltage of 
neither of the terminals with respect to the chassis GND 
exceed the ground proof voltage of + 180V 
• SINGLE VOLTAGE CONNECTION 
  For connection as shown in FIG.6.1, the output voltage 
will be the sum of individual supplies and output 
current will be limited to within the value specified for 
a single unit whichever is lower. For positive ground 
terminal to output positive point and for negative 
ground system, hook-up the ground terminal to the 
negative output point. 
• PLUS / MINUS CONNECTION 
  For connection as shown in FIG.6.2 where the intermediate 
point is hooked up to ground, the configuration can be used as 
Plus / Minus power supply. 
 

6.3.  PARALLEL OPERATION (MASTER /  
      SLAVE CONTROL) 
Two or more units of the same model can be hooked up in 
parallel to give an increase in output current capacity. The total 
output current capacity will be the sum of the output currents of 
the individual units. In this mode of operation, one supply will 
act as the master and all settings are from the master unit 
• Note: When connecting the supplies in parallel, be sure that 
all the power supplies are turned OFF. 
• HOOK-UP PROCEDURES 
1. Switch OFF the power of all units. 
2. Switch the master/slave switch, FIG.6.3, on all the slave  
units from “MASTER” to “SLAVE” position. 
3. Hook-up the IN/OUT terminals for MASTER/SLAVE  
operation as shown in FIG.6.3. 
4. Connect the output terminals of each of the units to the 
load as shown in FIG.6.4. For proper performance, use 
all cables of same length and thickness. 
5. Set the voltage and current adjustment knobs of all the 
slave units to the maximum position. 
6. Switch “ON” the MASTER unit and SLAVE units. 
The output voltage and current then can be 
controlled to the desired value via the adjustment 
knobs on the MASTER unit. 
  In the case of output goes to “0” ampere in the 
parallel operation mode, output voltage can no 
longer be controlled by the master machine. 
  Be sure to keep a minimum current flowing that is at 
least several percent of the rated current at all time. 
• CONNECTION OF TERMINAL ON REAR 
PANEL 
  While pressing on the slit portion of the terminal with a 
small screw driver, insert the connecting cable into the 
round hole. When insertion is completed, release the 
screw driver. (FIG.6.5) 
 

7. MAINTENANCE 
  WARNING: The following instructions are for use by qualified 
personnel only. To avoid electrical shock, do not perform any 
servicing other than those contained in the operating instructions 
unless you are qualified to do so. 
7.1 MAIN FUSE REPLACEMENT 
If the main fuse blows, the power on the LED indicator will not light 
and power supply will not operate. The fuse should not normally blow 
unless a problem has developed in the unit. Try to determine and 
correct the cause of the blown fuse, then replace only with a fuse of 
correct rating. The fuse is located on the rear panel and fuse rating can 
be found next to the fuse holder. If the problem persists, return the 
unit to the agent for further investigation. 
7.2  CALIBRATION 
This unit has accurately calibrated at the factory before shipment. Recalibration is recommended only if repairs have been made in a circuit 
affecting calibration accuracy, or if you have reason to believe the unit 
is out of calibration. 
However, calibrations should be attempted only if a 3½ digit 
multimeter with an accuracy of +0.5% DCV or better and a 0 
to 50ohm, 250 Watt adjustable resistive load is available. 
If re-calibration is required, use the following procedures. 
Locations of the electrical calibration on the main PCB are 
shown in FIG. 7.1. 
 

7.3. VOLTAGE CALIBRATION 
1. Connect the multimeter to measure the DC voltage across the  
power supply (+) and (–) output terminals. 
2. Turn on the power supply, and turn the panel VOLTAGE 
adjustment knob fully clockwise (maximum output). 
3. Adjust trimmer VR11 for a reading (Vmax. +0.5) ±0.1 volts  
on the multimeter. Vmax is the maximum normal output of 
the specific model under calibration. 
7.4. VOLTAGE ALIGNMENT 
1. Set the output voltage to about half the maximum allowable 
output for respective model. 
2. Align the voltmeter reading with the multimeter reading. 
  For BK Precision Analog series, adjust the trimmer VR-6 on 
the main PCB. 
  For BK Precision Digital series, adjust the trimmer VR-1 on 
the back of meter PCB. 
7.5.  CURRENT CALIBRATION 
1. Connect the 0 – 50ohm / 250W resistive load in series with  
the multimeter to measure the DC output current terminals. 
2. Adjust trimmer VR-5 fully anti-clockwise (referring to the 
component side). 
3. Adjust the output voltage to the maximum allowable 
output for respective model. 
4. Adjust the variable resistive load to obtain (Imax +0.1) 
±0.02 Ampere on the multimeter. Imax is the maximum 
nominal allowable output current of resistive model. 
5. Adjust trimmer VR-5 clockwise slowly until the limiting 
point is just reached and the C.C. LED lights up at the 
same time. 
7.6.  AMMETER ALIGNMENT 
1. Adjust the output voltage to half of its maximum allowable 
output voltage for respective model. 
2. Adjust the variable resistive load to obtain half of its 
maximum allowable current for respective model. 
3. Align the ammeter reading with the multimeter reading. 
  For BK Precision Analog series, adjust the trimmer VR-7 
on the main PCB. 
  For BK Precision Digital series, adjust the trimmer VR-2 
on the back of meter PCB. 
 

Limited One-Year Warranty 
B&K Precision Corp. warrants to the original purchaser that its products and the component parts thereof, will be free from defects in workmanship and 
materials for a period of three years from date of purchase. 
B&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 of a sales receipt. 
To help us better serve you, please complete the warranty registration for your new instrument via our website www.bkprecision.com 
Exclusions: This warranty does not apply in the event of misuse or abuse of the product or as a result of unauthorized alterations or repairs. The 
warranty is void if the serial number is altered, defaced or removed. 
B&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 limitations of incidental or consequential damages. So the above limitation or exclusion may not apply to you. 
This warranty gives you specific rights and you may have other rights, which vary from state-to-state. 
B&K Precision Corp. 
22820 Savi Ranch Parkway 
Yorba Linda, CA 92887 
www.bkprecision.com 
714-921-9095 
 

Service Information 
Warranty Service: Please go to the support and service section on our website at www.bkprecision.com to obtain a RMA #. Return the product in the 
original packaging with proof of purchase to the address below. Clearly state on the RMA the performance problem and return any leads, probes, 
connectors and accessories that you are using with the device. 
Non-Warranty Service: Please go to the support and service section on our website at www.bkprecision.com to obtain a RMA #. Return the product 
in the original packaging to the address below. Clearly state on the RMA the performance problem and return any leads, probes, connectors and 
accessories that you are using with the device. Customers not on an open account must include payment in the form of a money order or credit card. For 
the most current repair charges please refer to the service and support section on our website. 
Return all merchandise to B&K Precision Corp. with prepaid shipping. The flat-rate repair charge for Non-Warranty Service does not include return 
shipping. Return shipping to locations in North America is included for Warranty Service. For overnight shipments and non-North American shipping 
fees please contact B&K Precision Corp. 
B&K Precision Corp. 
22820 Savi Ranch Parkway 
Yorba Linda, CA 92887 
www.bkprecision.com 
714-921-9095 
Include with the returned instrument your complete return shipping address, contact name, phone number and description of problem. 
 

22820 Savi Ranch Parkway 
Yorba Linda, CA 92887 
www.bkprecision.com 
© 2014-2017 B&K Precision Corp. 
Printed in China                                                    PN# 481-375-9-001 
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