HP 6259B Service manual

REGULATED DC POWER SUPPLY
MODELS 6259B, 6260B,
6261B, 6268B, 6269B
* OPERATING AND SERVICE MANUAL FOR
MODEL 6259B, SERIALS 1535A-00651 AND ABOVE
MODEL 6260B, SERIALS 1545A-01026 AND ABOVE
MODEL 6261B, SERIALS 1543A-00551 AND ABOVE
MODEL 6268B, SERIALS 1539A-01481 AND ABOVE
MODEL 6269B, SERIALS 1535A-01631 AND ABOVE
* For instruments with serial numbers above those
listed, a change page may be included.
HP Part No. 5950-1766 Printed: March, 1976

TABLE OF CONTENTS
Section Page
I GENERAL INFORMATION _1-1
1-1 DESCRIPTION .11
1-8 SPECIFICATIONS .1-1
1-10 OPTIONS .1-2
1-12 INSTRUMENT/MANUAL
IDENTIFICATION.1-2
1- 15 ORDERING ADDITIONAL
MANUALS .1-3
II INSTALLATION . 2 1
2- 1 INITIAL INSPECTION.2-1
2-3 Mechanical Check .2-1
2-5 Electrical Check.: . . 2-1
2-7 INSTALLATION DATA .2-1
2-9 Location and Cooling .2-1
2-11 Outline Diagram.2-1
2-13 Rack Mounting .2-1
2-15 INPUT POWER
REQUIREMENTS .2-1
2-17 INPUT LINE VOLTAGE OR
FREQUENCY CONVERSION . 2-2
2-20 Converting a Standard Instrument
to 208-Volt Operation (Models
6259B, 6261 B, and 6268BL . . 2-2
2-22 Converting a Standard Instrument
to 208-Volt Operation (Models
6260B and 6269B).2-2
2-24 Converting a Standard Instrument
to 115-Volt Operation (Models
6259B, 6261 B, and 6268B). . . 2-2
2-26 Converting a Standard Instrument
to 115-Volt Operation (Model
6260B) .2-3
2-28 Converting a Standard Instrument
to 50Hz Operation .2-3
2 30 INPUT POWER CONNECTIONS . 2-3
2- 32 REPACKAGING FOR
SHIPMENT.24
II! OPERATING INSTRUCTIONS .3-1
3- 1 TURN-ON CHECKOUT
PROCEDURE.3-1
3-3 OPERATING MODES.3-2
3 6 NORMAL OPERATING MODE. . 3-2
3-8 Constant Voltage Operation .... 3-2
3-10 Constant Current Operation .... 3-2
3-12 Overvoltage Trip Point
Adjustment.3-2
Section Page
III 3-15 Connecting The Load .3-3
(con't.) 3-20 Operation With No Load.3-3
3-22 Operation Beyond Rated
Output .3-3
3-24 OPTIONAL OPERATING
MODES.3-3
3-27 Remote Voltage Sensing .3-3
3-34 Remote Programming .3-5
3-51 Auto-Parallel Operation.3-8
3-57 Auto-Series Operation.3-8
3-67 Auto-Tracking Operation.3-10
3-76 SPECIAL OPERATING
CONSIDERATIONS.3 12
3-77 Pulse Loading.3-12
3-79 Output Capacitance.3-12
3-82 Reverse Voltage Protection .... 3-12
3-85 Reverse Current Loading.3-12
3-87 Battery Charging.3-12
3- 91 Battery Discharging.3-13
IV PRINCIPLES OF OPERATION . . 4 1
4- 1 OVERALL BLOCK
DIAGRAM DISCUSSION_4-1
4-16 DETAILED CIRCUIT
ANALYSIS.4-3
4-17 Preregulator Control Circuit .... 4-3
4-27 Overvoltage Limit Circuit.4-4
4-29 Series Regulator and Driver .... 4-4
4-31 Short-Circuit Protection .4-4
4-33 Constant-Voltage Comparator ... 4-4
4-40 Constant-Current Comparator ... 4-5
4-45 Voltage Clamp Circuit.4-6
4-48 Mixer and Error Amplifiers .... 4-6
4-52 Overvoltage Protection Crowbar. . 4-6
4-58 Turn-On Control Circuit .4-7
4-61 Reference Regulator.4-7
4-66 Meter Circuit.4-7
4- 70 Additional Protection Features . . 4-7
V MAINTENANCE.5-1
5- 1 INTRODUCTION .5-1
5-3 TEST EQUIPMENT
REQUIRED.5-2
5-5 PERFORMANCE TEST.5-2
5-7 CONSTANT-VOLTAGE TESTS. . 5-2
5 38 CONSTANT-CURRENT TESTS. . 5-6
5-49 TROUBLESHOOTING.5-8
iii

TABLE OF CONTENTS (Continued)
Section Page Section
Page
V
5-54
OVERALL TROUBLE-
V
5-100 Ripple Balance Adjustment . . . 5-19
(con't.) SHOOTING PROCEDURES
. 5-8
(con't.)
5-102
Preregulator Tracking
5-60
Disassembly Procedures . . 5-15 Adjustment . . . 5-20
5-69 REPAIR AND REPLACEMENT
. 5-16
5-104 Crowbar Trip Voltage
5-71 ADJUSTMENT AND
Adjustment. . . 5-20
CALIBRATION .
. 5-16
5-106
Maximum Crowbar Trip
5-73
Meter Zero Adjustment. . 5-16
Voltage Adjustment.
. . 5-20
5-75
Voltmeter Calibration .
. 5-16
5-108
Disabling the Crowbar . . . .
. . 5-20
5-77 Ammeter Calibration .
. 5-17
5-79
Constant-Voltage Programming VI REPLACEABLE PARTS . . . 6-1
Calibration.
. 5-17
5-89
Constant-Current Programming
VII CIRCUIT DIAGRAM AND
Calibration.
. 5-18
COMPONENT LOCATION
5-98 Load Transient Recovery Time DIAGRAMS . . . 7-1
Adjustment .
. 5-19
IV

SECTION I
GENERAL INFORMATION
1-1 DESCRIPTION
1 -2 The five constant-voltage/constant current power
supply models included in this manual use a transistor
series-regulator combined with a triac preregulator for high
efficiency, excellent regulation, and low ripple and noise.
These supplies are packaged in 7-inch high full-rack-width
cabinets that are suitable for either bench or relay rack
operation.
1 -3 The outputs of these supplies can be varied from
zero to full rated voltage or current by setting coarse and
fine voltage and current controls on the front panel or they
can be programmed remotely by resistance or voltage inputs
to rear panel terminals. When the voltage controls are used
to establish a constant output voltage, the current controls
establish a current limit that can protect the load from over¬
current. When the current controls are used to establish a
constant output current, the voltage controls establish a
voltage limit that can protect the load from excessive
voltage. The crossover from constant-voltage to constant-
current operation, or vice versa, occurs automatically when
the load current reaches the value established by the current
controls or the voltage reaches the value established by the
voltage controls. The output voltage and current can both
be monitored continuously on front panel meters.
1-4 Output loads are further protected by a built-in
fast-acting overvoltage protection crowbar circuit that
automatically shorts the supply's output terminals if a
preset voltage limit is exceeded. A front panel control sets
the voltage at which the crowbar trips and can be adjusted
from approximately 10% to 110% of the supply's maximum
rated voltage. When several supplies are installed in the
same system, whether in series, parallel, or independently,
their crowbar circuits can be interconnected so that all will
trip simultaneously whenever any one of them does.
1 -5 These power supplies are forced air cooled.
1-6 The ac input connections to these supplies are made
at rear panel terminals. All dc output, remote sensing, and
remote programming connections are also made at rear
panel terminals. Either the positive or negative output
terminal of a supply may be grounded or the supply's
output may be floated at up to 300 volts above ground.
1-7 Remote programming, remote sensing, and several
methods of operating supplies in combination of two or
three are made possible by rear panel terminals that allow
access to control points within the regulator circuits. These
capabilities are described below.
a. Remote Programming. The power supply's output
voltage or current (or both) can be controlled from a remote
location by varying a resistance or a voltage input signal to
the supply's voltage or current regulator circuit.
b. Remote Sensing. Connecting the voltage regulator's
feedback circuit to the load terminals rather than to the
supply's output terminals prevents the voltage drop in the
load leads from impairing voltage regulation at the load
when operating in the constant voltage mode. A separate
pair of sensing leads which carry no load current extend
the feedback loop to the load terminals.
c. Auto-Parallel Operation. Two or three similar
supplies connected in parallel can be made to share loads
equally and can be controlled by the voltage and current
controls (or remote programming terminals) of one of the
supplies designated the master if they are connected for
auto-parallel operation. Normally, only supplies having
the same model number are connected in auto-parallel, but
auto-parallel operation can be used with any of the supplies
covered by this manual that have equal current capabilities.
d. Auto-Series Operation. Two or three supplies can
be connected in series and have their outputs simultaneously
controlled by the voltage and current controls (or remote
programming terminals) of one of the supplies designated
the master. The voltage contributed by each slave is main¬
tained in a constant ratio to that of the master. These
ratios can be set as desired. Auto-series operation provides
higher output voltages in constant voltage operation and
greater voltage compliance in constant current operation.
Any HP supply that offers auto-series operation can serve
as a slave supply; the master supply does not have to be an
auto-series model.
e. Auto-Tracking Operation. Auto-tracking is similar
to auto-series operation except that two or three supplies
share a common negative output bus and are interconnected
so that the output voltage of each slave supply is maintained
at some constant fraction of that of the master supply. All
of the supplies are controlled through the master supply,
and each supply feeds a separate load.
1-8 SPECIFICATIONS
1-9 Detailed specifications for these power supplies
are given in Table 1 -1.
M

1-10 OPTIONS
Option No.
Description
1-11 Options are customer-requested factory modifica¬
tions of a standard instrument. The following options are
available for the instruments covered by this manual. Where
necessary, detailed coverage of the options is included
throughout the manual.
Option No. Description
005 Realign ment for 50Hz Operation : Standard
instruments are designed for 57 to 63Hz
operation. For 50Hz operation, a resistor
in the preregulator control circuit is changed
and the preregulator is realigned.
007 T en-Turn Output Voltage Control: A ten-
turn control replaces the coarse voltage con¬
trol for improved resolution in setting the
output voltage.
008 Ten-Turn Output Current Control: A ten-
turn control replaces the coarse current
control for improved resolution in setting
the output current.
009 Ten-Turn Output Voltage and Current
Control s: This option includes Options
007 and 008 in the same instrument.
010 C hassis Slides : Factory installed slides
permit convenient access to the interior of
a rack mounted supply for maintenance.
013 Three-Digit Graduated Decadial Voltage
Control: To improve mechanical stability
and permit accurate resetting of the output
voltage, Option 013 replaces the coarse
voltage control with a ten-turn control
equipped with a 3-digit turns-counting dial.
014 Three-Digit Graduated Decadial Current
Control : To improve mechanical stability
and permit accurate resetting of the output
current. Option 014 replaces the coarse
current control with a ten-turn control
equipped with a 3-digit turns-counting dial.
016 Rewiring for 11 5Vac ±10% Single-Phase
Input (Model 6260B only): This factory
modification replaces the circuit breaker
and power transformer, adds a resistor to the
A2 assembly, and reconnects the bias trans¬
former, preregulator choke, and fans for
11 5Vac operation.
020 Adjustable Voltage Programming : Two
screwdriver-adjustable controls accessible
through holes in the rear panel allow the
voltage programming coefficient and zero
output voltage to be adjusted conveniently
to an accuracy of 0.1%.
021 Adjustable Current Programming: Two
screwdriver-adjustable controls accessible
through holes in the rear panel allow the
current programming coefficient and zero
output current to be adjusted conveniently
to an accuracy of 0.1%.
022 Adjustable Voltage and Current Programming:
This option includes Options 020 and 021
in the same instrument.
026 Rewiring for 11 5Vac ±10% Single-Phase
Input (Models 6259B, 6261 B, and 6268B only):
This factory modification replaces the circuit
breaker (except in the Model 6259B), adds
a resistor to the A2 assembly, and reconnects
the power transformer, bias transformer,
preregulator choke, and fans for 115Vac
operation.
027 Rewiring for 208Vac +10% Single-Phase
Input: This factory modification reconnects
the power and bias transformers for 208Vac
operation.
040 Interfacing for Mu ltiprogrammer Operation :
This factory modification prepares standard
power supplies for resistance programming
by the 6940B Multiprogrammer or the
6941 B Multiprogrammer Extender. Operation
with either of these instruments requires that
the power supply be subjected to a special
calibration and a protection checkout. The
special calibration insures that the power
supply can be accurately set to zero and to
the maximum rated output voltage or current
when programmed by the multiprogrammer.
The protection checkout insures that the
power supply will not be damaged by the
rapid repetitive programming possible with
the multiprogrammer. This option includes
Option 022.
1-12 INSTRUMENT/MANUAL IDENTIFICATION
1-13 Hewlett-Packard power supplies are identified by a
1-2

two-part serial number. The first part is the serial number
prefix, a number-letter combination that denotes the date
of a significant design change and the country of manu¬
facture. The first two digits indicate the year (10 = 1970,
11 = 1971, etc.), the second two digits indicate the week,
and the letter "A” designates the U. S. A. as the country
of manufacture. The second part is the power supply serial
number. A different sequential number is assigned to each
power supply, starting with 001 01.
1-14 If the serial number on your instrument does not
agree with those on the title page of the manual. Change
Sheets supplied with the manual define the differences
between your instrument and the instrument described
by this manual.
1-15 ORDERING ADDITIONAL MANUALS
1-16 One manual is shipped with each power supply.
Additional manuals may be purchased from your local
Hewlett-Packard field office (see list at rear of this manual
for addresses). Specify the model number, serial number
prefix, and HP part number shown on the title page.
Table 1-1 Specifications: Models 6259B, 6260B, 6261B, 6268B, 6269B
INPUT:
230Vac ±10%, single phase, 57-63Hz for the standard
models. (For other input voltages or 50Hz operation, see
the option listings in paragraph 1-10. Input power require¬
ments are listed in paragraph 2-1 5.
OUTPUT:
Model 6259B 0-10 volts at 0-50 amps
6260B 0-10 volts at 0-100 amps
6261 B 0-20 volts at 0-50 amps
6268B 0-40 volts at 0-30 amps
6269B 0-40 volts at 0-50 amps
LOAD EFFECT (LOAD REGULATION):
Constant Voltage — Less than 0.01% of output plus 200pV
for a load change equal to the current rating of the supply.
Constant Current —
Models 6259B and 6261 B - Less than 0.02% of output
plus 1 mA for a load change equal to the voltage rating of
the supply.
Models 6260B, 6268B, and 6269B - Less than 0.02%
of output plus 2mA for a load change equal to the voltage
rating of the supply.
SOURCE EFFECT (LINE REGULATION):
Constant Voltage - Less than 0.01 % of output plus
200pV for a change in line voltage between 208 and 254Vac
(or 104 and 1 27Vac) at any output voltage and current
within rating.
Constant Current -
Models 6259B and 6261 B - Less than 0.02% of output
plus 1 mA for a change in line voltage between 208 and 254Vac
(or 104 and 127Vac) at any output voltage and current
within rating.
Models 6260B, 6268B, and 6269B - Less than 0.02%
of output plus 2mA for a change in line voltage between
208 and 254Vac (or 104 and 127 Vac) at any output voltage
and current within rating.
PARD (RIPPLE AND NOISE):
(Measured within 20Hz to 20MHz bandwidth)
Model
Constant Voltage
Constant Current
6259B
500pVrms/5mV p-p
25mA rms
6260B
500pVrms/5mV p-p 50mA rms
6261 B
500pVrms/5mV p-p 25mA rms
6268B
1 mVrms/5mV p-p 20mA rms
6269B
1mVrms/5mV p-p 25mA rms
TEMPERATURE COEFFICIENT:
Constant Voltage - Less than 0.01% plus 200pV change
in output per degree Celsius change in ambient following
a 30-minute warmup.
Constant Current -
Models 6259B, 6261 B, and 6269B - Less than 0.01 %
plus 4mA change in output per degree Celsius change in
ambient following a 30-minute warmup.
Model 6260B - Less than 0.01 % plus 8mA change
in output per degree Celsius change in ambient following
a 30-minute warmup.
Model 6268B - Less than 0.01% plus 2mA change
in output per degree Celsius change in ambient following
a 30-minute warmup.
DRIFT (STABILITY):
(Change in output (dc to 20Hz) over an 8-hour interval
under constant line, load, and ambient temperature follow¬
ing a 30-minute warmup.)
Constant Voltage - Less than 0.03% of output plus 2mV.
Constant Current —
Models 6259B, 6261 B, and 6269B - Less than 0.03%
of output plus 10mA.
Model 6260B - Less than 0.03% of output plus 20mA.
Model 6268B - Less than 0.03% of output plus 5mA.
1-3

Table 1-1 Specifications: Models 6259B, 6260B, 6261B, 6268B, 6269B (Continued)
LOAD TRANSIENT RECOVERY TIME:
Less than 50/Jsec is required for output voltage recovery
(in constant voltage operation) to within lOmV of the
nominal output following a change in output current equal
to the current rating of the supply or 5 amps, whichever
is smaller.
REMOTE PROGRAMMING COEFFICIENTS:
Output Voltage Programming —
Resistance
Voltage
Model Control (±1 %)
Control (±1%)
All Models
200JT2/V
1V/V
Output Current Programming —
Resistance Voltage
Model Control (±10%) Control (±10%)
6259B 4I2/A
lOmV/A
6260B 2£2/A 5mV/A
6261 B 4L2/A
10m V/A
6268B 6J2/A
16.7mV/A
6269 B
4L2/A 1 OrnV/A
REMOTE PROGRAMMING SPEED:
(Typical time required to nonrepetitively change from
zero to within 99.9% of the maximum rated output voltage
or from the maximum rated output
of that voltage above zero.)
voltage to within 0.1 %
Model
Up, Full Load Down, Full Load
6259B
70ms
10ms
6260B
70ms
5ms
6261 B
1 50ms
25ms
6268B
300ms
30ms
6269B
350ms
20ms
Model
Up, No Load Down, No Load
6259B
70ms
200ms
6260B
70ms
200ms
6261 B 1 50ms
250ms
6268B
300ms Isec
6269B
350ms Isec
PANEL METERS:
The accuracy of the front panel voltmeter and ammeter
is ±2% of full scale. The ranges of these meters are:
Model Model
6259B 12V,60A 6268B 50V,35A
6260B 12V, 120A 6269B 50V, 60A
6261 B 24V, 60A
TEMPERATURE RATINGS:
Operating 0 to 55'C Storage -40 to +75 C
COOLING:
These power supplies are forced air cooled. The Model
6259B is cooled by a single fan; the other models are cooled
by two fans.
RESOLUTION:
(Minimum output voltage or current change that can
be obtained using the front panel controls.)
Model Constant Voltage Constant Current
6259 B 1 m V 50mA
6260B 1 mV 100mA
6261B 2mV 50mA
6268B 5m V 30mA
6269B 5m V 50mA
OUTPUT IMPEDANCE (TYPICAL):
Approximated by a resistance in series with an inductance
as follows:
Model Model
6259B 0.05mft, IpH 6268B 0.2m£2, 1/uH
6260B 0.02m£2, IpH 6269B 0.1m£2, IpH
6261 B 0.01mS2, IpH
OVERVOLTAGE PROTECTION CROWBAR:
To avoid false tripping, the recommended trip margin
above the output voltage is 5% of the output voltage plus
2 volts for Models 6259B, 6260B, and 6261 B, and 5% of
the output voltage plus 1 volt for Models 6268B and 6269B.
The approximate crowbar trip voltage ranges are:
Model Model
6259B 2V-12V 6268B 4V-45V
6260B 2V-12V 6269B 4V-45V
6261 B 2V-23V
OPTIONS AVAILABLE:
(See paragraph 1-10 for descriptions)
All Models - Options 005, 007, 008, 009, 010, 013,
014, 020, 021, 022, 027, 040.
Model 6260B only — Option 016.
Model 6259B, 6261 B, and 6268B only — Option 026.
INPUT POWER CONNECTIONS:
Input power is connected by way of a 3-terminal barrier
Trip on the rear panel.
DIMENSIONS:
(See Figure 2-1 outline diagrams.)
WEIGHT:
Model
Net
Shipping
6259B
69 lbs. (31.3 kg)
78 lbs. (35.3 kg)
6260B 97 lbs. (43.9 kg) 106 lbs. (48.0 kg)
6261 B
78 lbs. (35.3 kg)
87 lbs. (39.4 kg)
6268B
76 lbs. (34.4 kg) 84 lbs. (38.1 kg)
6269B 89 lbs. (40.3 kg)
98 lbs. (44.0 kg)
1-4

SECTION II
INSTALLATION
2-1 INITIAL INSPECTION
2-2 Before shipment, this instrument was inspected
and found to be free of mechanical and electrical defects.
As soon as the instrument is unpacked, inspect for any
damage that may have occurred in transit. Save all
packing materials until the inspection is completed. If
damage is found, file a claim with the carrier immediately.
The Hewlett-Packard Sales and Service office should be
notified as soon as possible.
2-3 Mechanical Check
2-4 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 that the
meters are not scratched or cracked.
2-5 Electrical Check
2-6 The instrument should be checked against its
electrical specifications. Section V includes an "in-cabinet”
performance check to verify proper instrument operation.
2-7 INSTALLATION DATA
2-8 The instrument is shipped ready for permanent
rack installation or bench operation. It is necessary only
to connect the instrument to a source of power and it is
ready for use.
2-9 Location and Cooling
2-10 These instruments are fan-cooled and must be
installed with sufficient space for cooling air to reach their
sides. These power supplies should be used in an area
where the ambient temperature does not exceed 55"C.
2-11 Outline Diagram
2-1 2 Figure 2-1 shows the outline shape and dimensions
of these supplies.
2-13 Rack Mounting
2-14 This instrument is full rack size and can be easily
rack mounted in a conventional 19-inch rack panel using
standard mounting screws.
TERMINAL STRIP DETAIL
-esi;te
.*•:«»« 5.1 n sing
336=? tEPM
0 52 -!/«• 70
ffrON' Cl¥ENOCHS
6 9e8:ir?*<p' ■*
9C0C"4$2 6nr.' *1*
5 50'.4 8»t i
TOP
3'S
• 54 9mr»|
JJSCC --•».
SIDE
Figure 2-1. Outline Diagrams
(Models 6259B, 6260B, 6261B, 6268B, and 6269B)
2-15 INPUT POWER REQUIREMENTS
2-16 The standard instrument is wired for a nominal
input of 230Vac 57-63Hz when it is shipped from the factory.
The supplies covered by this manual are also available
equipped for a 208-volt input (Option 027), and except for
the Model 6269B, are also available equipped for a 115-volt
input (Option 026 for Models 6259B, 6261 B, and 6268B,
or Option 016 for the Model 6260B). In addition, all five
models are available in a 50Hz version. The input voltage
and frequency required is marked on the rear panel of the
supply. Except for the Model 6269B, which cannot be
converted to 11 5-volt operation, a standard instrument can
be converted by the user to 208 or 11 5-volt and to 50Hz
operation by following the instructions given in the follow¬
ing paragraphs. The standard instrument requires the input
current and power listed below when operated at full load
from a 230-volt source. When the supply is operated from
a 115-volt source, the input current is approximately twice
the amount listed.
Model Input Current Input Powe
6259B
6A
850W
6260B
12A
1600W
6261B
12A
1500W
6268B
12A 1600W
6269B
18A
2500W

2-17 INPUT LINE VOLTAGE OR
FREQUENCY CONVERSION
2-1 8 Converting a 230-volt instrument to 208-volt
operation is simply a matter of changing some taps or
jumper connections on main power transformer T1 and bias
transformer A3T2. Converting to 11 5-volt operation is
more involved. The Models 6259B, 6260B, 6261 B, and
6268B require an added resistor and some jumper changes
in the A2 RFI assembly and a changed A3T2 transformer
tap. In addition, the 6260B, 6261 B, and 6268B need a
replacement circuit breaker, and the 6260B needs a replace¬
ment T1 power transformer. Complete line voltage con¬
version instructions are given in paragraphs 2-20 through
2-27.
2-19 Converting a 60Hz instrument to 50Hz operation
requires that one resistor be replaced and some adjustments
be made. Line frequency conversion instructions are given
in paragraph 2-28.
2-20 Converting a Standard Instrument to 208-
Volt Operation (Models 6259B, 6261B and 6268B).
2-21 To convert these 230-volt instruments to 208-volt
operation, proceed as follows:
a. Disconnect instrument from power source and remove
top and bottom covers.
b. Remove A2 RFI assembly as described in steps (a)
through (c) of paragraph 5-65. This provides access to bias
transformer A3T2 (see Fig. 7-2).
c. Locate the wire that connects circuit breaker CB1 to
the A3T2 bias transformer terminal marked "230V”,
disconnect it from the transformer, and reconnect it to
the terminal marked "208V". Leave the wire from fan B2
(not used in the 6259B) connected to the terminal marked
"230V" (see Fig. 2-2B).
d. Re-install the RFI assembly by reversing the proce¬
dure of step (b) above.
e. Unsolder the wire connected to terminal 5 of power
transformer T1 and solder it instead to terminal 4 (see
Figure 2-3B).
2-22 Converting a Standard Instrument to 208-
Volt Operation (Models 6260B and 6269B).
2-23 To convert these 230-volt instruments to 208-
volt operation, proceed as follows:
a. Perform steps (a) through (d) of paragraph 2-21.
b. Unsolder the wire connected to the terminal marked
"230V" on power transformer T1 and solder it instead to
the terminal marked "208V" (see Fig. 2-4B).
2-24 Converting a Standard Instrument to 115-
Volt Operation (Models 6259B, 6261B and 6268B).
A
BIAS TRANSFORMER
(A3T2) CONNECTIONS
FOR 230 VOLT
OPERATION.
B
BIAS TRANSFORMER
(A3T2) CONNECTIONS
FOR 208 VOLT
OPERATION.
C
BIAS TRANSFORMER
(A3T2) CONNECTIONS
FOR 115 VOLT
OPERATION.
NOTE- X FAN B2 IS NOT USED
IN MODEL 62596
Figure 2-2. Bias Transformer Primary Connections
for 208Vac Operation (Modal 6259B, 6260B, 6261B,
6268B, and 6269B) and 115Vac Operation
(except Model 6269B).
2-2

2-25 To convert these 230-volt instruments to 11 5-volt
operation, proceed as follows:
a. (Omit this step for the Model 6259B.) Obtain and
install a new circuit breaker CB1. Refer to Option 026 in
the Table 6-4 parts list for its current rating and HP Part
Number. Connections to the replacement are the same as
those to the original breaker.
b. Remove and partially disassemble the A2 RFI
assembly as described in steps (a) through (d) of paragraph
5-65.
c. Unsolder jumper J3 from the A2 circuit board (see
Fig. 7-1) and install jumpers J1 and J2. Also install
resistor A2R3 on the circuit board. Refer to Option 026
in the Table 6-4 parts list for its description and HP Part
Number. Replace cover on RFI assembly.
d. Locate the wire that connects circuit breaker CB1
to the A3T2 bias transformer terminal marked "230V”,
disconnect it from the transformer, and reconnect it to
the terminal marked "115V." Also disconnect the wire
from fan B2 (not used in the 6259B) from the terminal
marked "230V" and reconnect it to the terminal marked
"0V” (see Fig. 2-2C).
e. Re-install the RFI assembly by reversing the
procedure of step (b).
f. Unsolder the jumper connecting terminals 2 and 3
of power transformer T1 (see Fig. 2-3C) and solder jumpers
between terminals 1 and 3, and 2 and 5.
2-26 Converting a Standard Instrument to 115-
Volt Operation (Model 6260B)
2-27 To convert the standard Model 6260B to 11 5-volt
operation, proceed as follows:
a. Obtain and install a new power transformer (T1) and
a new circuit breaker (CB1). Refer to Option 016 in the
Table 6-4 parts list for their description and HP Part
Number. The new transformer has two primary terminals.
Transfer the wire from the ”0V" terminal on the old trans¬
former to the "0V" on the new one, and from the ”230V”
terminal on the old one to the "115V'' terminal on the
new one. The connections to the replacement circuit
breaker are the same as to the old one.
b. Perform steps (b) through (e) of paragraph 2-25.
2-28 Converting a Standard Instrument to 50Hz
Operation
2-29 To convert a 60Hz instrument to 50Hz operation,
proceed as follows:
a. Replace A1 R82 with a 240 ohm 5% 1/2-watt resistor.
Refer to the Table 6-4 parts list under Option 005 for the
HP Part Number of a suitable replacement.
b. After replacing A1 R82, perform the preregulator
tracking adjustment given in paragraph 5-102.
c. Check the ripple balance adjustment by the procedure
given in paragraph 5-100.
2-31 No input power cable is supplied with the instru¬
ments covered by this manual. Input power connections
are made to a 3-terminal barrier block on the rear panel.
Its center terminal is grounded to the instrument chassis.
To protect operating personnel, the National Electrical
Manufacturers Association (NEMA) recommends that the
instrument panel and cabinet be grounded. The user-
supplied power cable should have three conductors (with
the third conductor grounded) and should be of adequate
wire size to handle the input current drawn by the supply
(see paragraph 2-15). Note that when the supply is opera¬
ted from a 11 5-volt source, the input current is approxi¬
mately twice that shown in paragraph 2-1 5.
2-3

2-32 REPACKAGING FOR SHIPMENT
2*33 To insure safe shipment of the instrument, it is
recommended that the package designed for the instrument
be used. The original packaging material is reusable. If it
is not available, contact your local Hewlett-Packard field
office to obtain the materials. This office will also furnish
the address of the nearest service office to which the
instrument can be shipped and provide the Authorized
Return label necessary to expedite the handling of your
instrument return. Be sure to attach a tag to the instrument
which specifies the owner, model number, full serial number,
and service required, or a brief description of the trouble.
ov
A
INPUT POWER
TRANSFORMER [TO
CONNECTIONS FOR
230 VOLT OPERATION.
OV
B
INPUT POWER
TRANSFORMER (Tl)
CONNECTIONS FOR
208 VOLT OPERATION.
Figure 2-4. Power Transformer Tl Primary Connections
for 208Vac Operation (Model 6260B and 6269B)
2-4

SECTION III
OPERATING INSTRUCTIONS
Figure 3-1. Front Panel Controls and Indicators
3-1 TURN-ON CHECKOUT PROCEDURE
3-2 The following steps describe the use of the front
panel controls and indicators illustrated in Figure 3-1 and
serve as a brief check that the supply is operational. This
checkout procedure or the more detailed performance
test of paragraph 5-5 should be followed when the instru¬
ment is received and before it is connected to any load
equipment. Proceed to the more detailed test and trouble¬
shooting procedures in Section V if any difficulties are
encountered.
a. Turn CURRENTcontrols (7) and OVERVOLTAGE
ADJUST potentiometer (5) fully clockwise and check
that rear panel straps are connected as shown in Figure 3-2,
but do not connect load R^.
b. Connect ac power of the appropriate voltage and
frequency to the rear panel ac and acc terminals. The
supply's input rating is identified on its rear panel.
-CAUTION-
Do not interchange the ac and acc input lines;
connect the ac input terminal to the hot side
and the acc input terminal to the grounded
side of the ac line. Do not fail to connect the
input ground terminal < ± ) securely to an
external earth ground.
c. Set LINE switch or circuit breaker (7) ON and
observe that pilot lamp (2) lights.
d. Adjust COARSE and FINE VOLTAGE controls @
for desired indication on voltmeter ©
e. Ensure that overvoltage crowbar circuit is operational
by slowly turning OVERVOLTAGE ADJUST control ©
counterclockwise with a screwdriver until OVERVOLTAGE
lamp © lights and voltmeter indication drops to zero
volts.
3-1

f. Reset crowbar by returning OVERVOLTAGE
ADJUST control to its maximum clockwise position and
turning off the supply. On turning the supply back on,
the voltage should be the same value as was set in step (d).
g. To check the constant current circuit, first turn off
the supply, connect a short across the output bus bars
(see Figure 3-2), and turn it back on.
h. Adjust COARSE and FINE CURRENT controls (7)
until ammeter (8) indicates desired output current or
current limit. (The VOLTAGE controls must be set for
a greater-than-zero output to obtain the output current
programmed.)
i. Turn off the supply, remove the short from its out¬
put, and read the remainder of these operating instructions
before connecting the supply to an actual load.
3-3 OPERATING MODES
3-4 This power supply is designed so that its mode of
operation can be selected by making strapping connections
between terminals on its rear panel. The following para¬
graphs first describe normal operation using the normal
strapping pattern as it is connected at the factory. Later
paragraphs cover some optional operating modes including
remote voltage sensing, remote programming, and some
methods of operating these power supplies in combinations
of two or three.
3-5 The DC Power Supply Handbook, Application
Note 90A, is a useful source of additional information on
using regulated power supplies effectively. This 138-page
handbook includes chapters on operating principles, ac
and load connections, optional operating modes, and
performance measurements and is available at no charge
from your local HP sales office. The address of your local
sales office can be found in the back of this manual.
3-6 NORMAL OPERATING MODE
3-7 This power supply was shipped with the proper
rear panel strapping connections made for constant-voltage/
constant-current operation with local sensing and local
programming. This strapping pattern is illustrated in
Figure 3-2. By means of the front panel voltage and current
controls, the operator selects either a constant-voltage or a
constant-current output. Whether the supply functions in
the constant-voltage or the constant-current mode depends
on the settings of the voltage and current controls and on
the resistance of the output load. For values of load resis¬
tance greater than a critical crossover value equal to the
voltage setting divided by the current setting, the supply
operates in the constant-voltage mode. With a load resis¬
tance smaller than this critical value, it operates in the
constant-current mode. The transition occurs automati¬
cally; no switches need to be operated or connections
changed.
EXT.
CROWBAR
TRIGGER
' + - ' AI A2 A3 A4 A5 A6 A7 A8 fS -S A9
i
IE 3E
p 0
r t-i
5
-OUT
-0
+ OUT
Figure 3-2. Normal Strapping Pattern
3-8 Constant Voltage Operation
3-9 To adjust the supply for constant voltage operation:
a. Turn on supply and, with output terminals open,
adjust the VOLTAGE controls for the desired output
voltage. Then turn power off.
b. Connect a short across the rear panel output terminals,
restore power, and adjust the CURRENT controls for the
desired maximum output current. Then remove the short.
If a load change causes this current limit to be exceeded,
the supply automatically crosses over to constant current
operation at this preset current limit and the output voltage
drops proportionately. In setting the current limit, make
an adequate allowance for high peak currents that could
cause unwanted crossover. (Refer to paragraph 3-77.)
3-10 Constant Current Operation
3-11 To adjust the supply for constant current operation;
a. Connect a short across the rear output terminals, turn
the power on, and adjust the CURRENT controls for the
desired output current.
b. Open the output terminals and adjust the VOLTAGE
controls for the desired maximum output voltage. If a
load change causes this voltage limit to be exceeded, the
supply automatically crosses over to constant voltage opera¬
tion at this preset voltage limit and the output current drops
proportionately. In setting the voltage limit, make an
adequate allowance for high peak voltages that could cause
unwanted crossover. (Refer to paragraph 3-77.)
3-12 Overvoltage Trip Point Adjustment
3-13 The crowbar trip voltage is adjusted by using the
screwdriver control on the front panel. The approximate
trip voltage ranges are listed in Table 1 -1. When the crowbar
trips, an SCR shorts the output and the amber OVER¬
VOLTAGE indicator on the front panel lights. Rotating
the control clockwise sets the trip voltage higher. (It is set to
maximum at the factory.) Paragraph 5 108 contains instruc¬
tions for completely disabling the crowbar, if this is desired.

3-14 When adjusting the crowbar trip point, the
possibility of false tripping must be considered. If the trip
voltage is set too close to the supply's operating voltage,
a transient in the output would falsely trip the crowbar.
For this reason it is recommended that the crowbar be set
higher than the output voltage by 5% of the output voltage
plus 2 volts for the Models 6259B, 6260B, or 6261 B, or
5% of the output voltage plus one volt for the Models 6268B
or 6269B. If an occasional tripping of the crowbar can be
tolerated as a load is being disconnected, the crowbar trip
point can be set much closer to the operating voltage of
the supply.
3-15 Connecting The Load
3-16 To satisfy the requirements of safety, the wires to
the load should be at least heavy enough not to overheat
while carrying the power supply current that would flow if
the load were shorted. Generally, heavier wire than this is
required to obtain good regulation at the load. If the load
regulation is critical, use remote voltage sensing. (Refer to
paragraph 3-27.)
3-1 7 If multiple loads are connected to one supply,
each load should be connected to the supply's output
terminals using separate pairs of connecting wires. This
minimizes mutual coupling effects between loads and takes
full advantage of the supply's low output impedance. Each
pair of connecting wires should be as short as possible and
twisted or shielded to reduce noise pickup.
3-18 If load considerations require the use of output
distribution terminals that are located remotely from the
supply, then the power supply output terminals should
be connected to the remote distribution terminals by a
pair of twisted or shielded wires and each load should be
separately connected to the remote distribution terminals.
Remote voltage sensing would be required under these
circumstances. (Refer to paragraph 3-27.)
3-1 9 Either positive or negative voltages can be obtained
from this supply by grounding one of the output terminals
or one end of the load. Always use two wires to connect
the load to the supply regardless of where or how the
system is grounded. Never ground the system at more than
one point. This supply can be operated up to 300 volts
above ground if neither output terminal is grounded.
3-20 Operation With No Load
3-21 When the supply is operated without a load, its
down-programming speed is considerably slower than when
its output is loaded. This slower programming speed is
evident whether the VOLTAGE controls are turned fully
counterclockwise or an external voltage programming input
signal is decreased. When the crowbar is activated during
no-load operation, the supply's output falls rapidly to about
two volts and then decreases more slowly towards zero.
The actual time required for the output to fall from two
volts to zero varies from several seconds to several minutes,
depending on the output rating of the supply.
3-22 Operation Beyond Rated Output
3-23 The supply may be able to provide voltages and
currents greater than its rated maximum outputs. Operation
can extend into the shaded areas on the meter face without
damage to the supply, but performance cannot be guaranteed
to meet all specifications.
3-24 OPTIONAL OPERATING MODES
3-25 The optional operating modes discussed in the
following paragraphs include:
a. Remote voltage sensing
b. Remote programming
c. Auto-Parallel operation
d. Auto-Series operation
e. Auto-Tracking operation
Special operating instructions for instruments equipped
with Option 040 to permit their interfacing with a Model
6940B Multiprogrammer or a 6941 B Multiprogrammer
Extender are not included but can be found in the manual
covering the programmable resistance cards that are neces¬
sary to complete the interface. Special calibration instruc¬
tions for power supplies equipped with Option 040 are
included in Section V of this manual.
3-26 By changing its rear panel strapping pattern
according to the instructions which follow, any of the
supplies covered by this manual can be operated in any
of the modes listed above.
-CAUTION-
Disconnect input ac power before changing any
rear panel connections and make certain all wires
and straps are properly connected and terminal
strip screws are securely tightened before
reapplying power.
3-27 Remote Voltage Sensing
3-28 Because of the unavoidable voltage drop developed
in the load leads, the normal strapping pattern shown in
Figure 3-2 will not provide the best possible voltage regula¬
tion at the load. If, for example, one were to use 4-gauge
wire to connect a load that is located only 5 feet from a
3-3

Model 6259B 10V 50A supply, the full-load regulation
measured at the load would be about 120 millivolts as com¬
pared to the 1.2 millivolt regulation that could be measured
at the supply's output terminals. Thus even relatively short
load leads can cause a considerable degradation of the sup¬
ply's performance. The remote sensing connections shown
in Figure 3-3 improve the voltage regulation at the load by
monitoring the voltage there instead of at the supply's
output terminals. (The advantages of remote sensing
apply only during constant voltage operation.)
3-29 As can be seen in Figure 3-3, remote sensing
involves removing the +S and —S jumpers from the output
terminals, connecting the load leads normally, and using
a separate pair of wires to connect the +S and —S sensing
terminals to the load. The following paragraphs discuss
some precautions that should be observed when making
a remote sensing installation.
NOTE
The +S jumper is the one that links the +S
terminal to the + OUT terminal when the
supply's terminals are strapped for normal
operation as shown in Figure 3-2. The -S
jumper is the one that links the -S terminal
to the -OUT terminal.
3-30 The load leads should be of the heaviest practicable
wire gauge, a t least heavy enough to limit the voltage drop
in each lead to 0.5 volt. This limitation is dictated by the
adverse effect that a greater load lead voltage drop has on
bias voltages within the supply when remote sensing is used.
Twisting the load leads may help to minimize noise pick-up.
While there are practical limitations on the distance that
can separate a power supply from its load when using remote
sensing, it isn't possible to define these limits precisely due
to a variety of factors that are unique to each particular
installation.
3-31 Since the sensing leads carry only a few milliamps,
the wires used for sensing can be much lighter than the
load leads (22 AWG is generally adequate), but they should
be a shielded, twisted pair to minimize the pickup of
external noise. Any noise picked up on the sensing leads
will appear at the supply's output. The shield should be
grounded at one end only and should not be used as one
of the sensing conductors. The sensing leads should be
connected as close to the load as possible.
3-32 The sensing leads are part of the supply's program¬
ming circuit, so they should be connected in such a way as
to make it unlikely that they might inadvertently become
open circuited. If the sensing leads were to open during
operation, the output voltage would tend to rise. Although
the increase would be limited by protective resistors R108
and R1 09, damage to the supply or to the load might occur
if the loss of sensing were accompanied by a load transient.
For this reason no switch, relay, or connector contacts
should be included in the remote sensing path.
-CAUTION--
When using remote voltage sensing, it is possible
to damage the supply by disconnecting a load
lead while the sensing lead is still connected and
the supply is energized. If a load lead becomes
disconnected, current flows through internal
protection resistors R108 and R109, the sensing
leads, and the load and may burn out the resistors.
Additional factors could compound the damage
caused by an opened load lead. If the output of
the supply is connected to an inductive load or a
battery *, or is connected in parallel with another
supply, then opening a load lead would allow
current from the external source to flow through
the sensing leads and damage the supply's input
circuits. If the crowbar fires, the damage could
even be greater.
For these reasons, if there is any risk of an opened
load circuit while remote sensing is used, 1/16-amp
fuses should be installed in both sensing leads.
Fuses in the sensing leads will not affect the
performance of the supply and should protect
against costly damage.
* Remote sensing is not recommended when charging or
discharging a battery. See paragraphs 3 87 and 3-91.
3-33 Another factor to be considered when making a
remote sensing installation is the inductance of the long
load leads. Although dc and low frequency performance
are improved by remote sensing, the higher inductance of
longer leads does impair transient response and could affect
3-4

the stability of the feedback loop seriously enough to cause
oscillation. If remote sensing disturbs the supply's stability,
try these two corrective measures:
a. Adjust the equalization control R47 until the oscilla¬
tion stops. To achieve the best possible transient response
for a given remote sensing installation, measure the transient
response using the procedure given in paragraph 5-27 and
adjust R47 while observing the transient response wave¬
forms.
b. If adjusting R47 does not eliminate the instability,
it may be beneficial to disconnect output capacitor A3C3
from the circuit and connect a similar capacitor directly
across the load. To gain access to capacitor A3C3, the
A2 RFI Assembly must first be removed. Follow steps (a)
through (c) of paragraph 5-65 to remove the A2 assembly.
Then unsolder the heavy wire from the A3 circuit board
that connects the positive terminal of A3C3 to the positive
output bus bar. (This heavy red-insulated wire is identified
in Figure 7-2 -)
NOTE
Do not unsolder the capacitor's negative lead.
The negative lead to A3C3 carries collector
current for transistor A4Q101 and would
disable the power supply if disconnected.
Tape the free end of the disconnected wire, replace the A2
assembly, and replace the bottom cover of the supply. The
substitute capacitor should have approximately the same
capacitance, an equal or greater voltage rating, and good
high frequency characteristics. Connect it directly across
the load using the shortest possible leads. Readjust equali¬
zation control R47 as in step (a) above after installing the
substitute output capacitor.
3-34 Remote Programming
3-35 The output voltage or current of these power
supplies can be remotely controlled by connecting an
external resistor or applying an external voltage to rear
panel terminals. If resistance programming is used, a
variable resistor can control the output over its entire
range. Or, a variable resistor connected in series with a
fixed resistor can have its control restricted to a limited
portion of the output range. Alternately, a switch can be
used to select fixed values of programming resistance to
obtain a set of discrete voltages or currents. (The switch
must have make-before-break contacts to avoid producing
the output voltage transients that momentarily opening
the programming terminals would cause.) To maintain
the temperature and stability specifications of the supply,
programming resistors must be stable, low noise resistors
with a temperature coefficient of less than 30ppm per C
and a power rating at least 30 times what they will actually
dissipate.
3-36 Both voltage and current outputs can also be
controlled through a voltage input. When voltage program¬
ming the output voltage, the choice can be made between
using a connection that produces a unity gain relationship
between input and output (paragraph 3-41) or another
connection that produces variable voltage gains (paragraph
3-42). Similarly, the output current can be programmed
using a connection that produces a fixed gain (paragraph
3-47) or a variable gain (paragraph 3-48).
3-37 Connecting a supply for remote voltage or current
programming disables the corresponding front panel controls.
3-38 The following paragraphs discuss in greater detail
the methods of remotely programming the output voltage
or current using either a resistance or a voltage input.
Whichever method is used, the wires connecting the pro¬
gramming terminals of the supply to the remote program¬
ming device must be shielded to reduce noise pickup. The
outer shield of the cable should not be used as a conductor
but should be connected to ground at one end only.
3-39 Constant Voltage Output, Resistance Input. The
rear panel connections shown in Figure 3-4 allow the out¬
put voltage to be varied by using an external resistor to
program the supply. The supply's constant voltage program¬
ming current determines its programming coefficient. In
the supplies covered by this manual, this programming
current is factory adjusted to within 1% of 5mA, resulting
in a programming coefficient of 200 ohms per volt. If a
greater programming accuracy is required, it can be obtained
either by changing resistor R3 as discussed in paragraph 5-86
or, if the instrument is equipped with Options 020 or 022,
by adjusting potentiometer R112 as discussed in paragraph
5 87.
3-40 With the programming terminals shorted (terminals
A2 to -S), the no-load output voltage of the supply should
be —1 5mV ±5mV. If a minimum output voltage is required
that is closer to zero than this, it can be obtained either
Figure 3-4. Resistance Programming of Output Voltage
3-5

by installing and adjusting R110 as discussed in paragraph
5-81 or, if the instrument is equipped with Option 020 or
022, by adjusting potentiometer R113 as discussed in
paragraph 5-83.
-CAUTION-
Do not allow programming terminals A2 or
—S to become open circuited while resistance
programming the output voltage. If they do
become open circuited, the supply's output
voltage tends to rise beyond its rated maximum.
If the supply's current controls and over¬
voltage crowbar trip point are properly adjusted,
however, no damage to the power supply or
load should result.
3-41 Constant Voltage Output, Voltage Input (Unity
Gain). The rear panel connections shown in Figure 3-5
allow the output voltage to be varied by using an external
voltage source to program the supply. In this mode, the
output voltage varies in a 1 to 1 ratio with the program¬
ming voltage. The load on the programming voltage source
is less than 20 microamperes. Impedance matching resistor
is required to maintain the temperature coefficient
and stability specifications of the supply. To adjust the
output voltage to exactly zero with a zero programming
voltage, follow the same instructions as are referred to in
paragraph 3-40.
3-42 Constant Voltage Output, Voltage Input (Variable
Gain). In the remote programming arrangement shown
in Figure 3-6, the series combination of external voltage
source Eg and reference resistor Rp replaces the supply's
internal voltage programming current source. As a result,
the voltage this external current source develops across
gain control R p becomes the output voltage of the supply,
and the gain relationship between Eg and the output volt¬
age equals the resistance ratio R p /Rp.
Figure 3-5. Voltage Programming of Output Voltage
(Unity Gain)
3-43 When using this programming technique, select
a value for Rp that is less than 10k ohms and that would
conduct at least 5 miiliamps if connected across the
programming voltage source with its voltage at the maximum
value of input voltage to be used. Once the value for R R
is selected, multiply Rp by the maximum voltage gain
desired to find R p . (If desired, the power supply's front
panel voltage controls can be used in place of external gain
control R p by deleting the external gain control from the
circuit and strapping together terminals A1 and A2.)
3-44 The output voltage of the supply can be adjusted
to exactly zero with a zero programming voltage input
either by installing and adjusting R111 as discussed in
paragraph 5-82 or, if the instrument is equipped with
Option 020 or 022, by adjusting potentiometer R11 2 as
discussed in paragraph 5-83.
3-45 Constant Current Output, Resistance Input. The
rear panel connections shown in Figure 3-7 allow the
output current to be varied by using an external resistor to
program the supply. The supply's constant current program¬
ming current, which is factory adjusted to 2.5mA ±10%,
determines the exact value of its programming coefficient.
The programming coefficients for the supplies included in
this manual are as follows:
Models 6259B 4 ohms/ampere
6260B 2 ohms/ampere
6261 B 4 ohms/ampere
6268B 6 ohms/ampere
6269B 4 ohms/ampere
If the ±10% accuracy of these coefficients is not adequate,
they may be adjusted either by changing resistor R30 as
discussed in paragraph 5-96 or, if the instrument is equipped
with Option 021 or 022, by adjusting potentiometer R116
as discussed in paragraph 5-97.
Figure 3-6. Voltage Programming of Output Voltage
(Variable Gain)
3-6

3-46 With zero ohms connected across the programming
terminals, the output current of the supply may be set to
exactly zero either by installing and adjusting R11 7 as
described in paragraph 5-91 or, if the instrument is equipped
with Option 021 or 022, by adjusting potentiometer R11 9
as discussed in paragraph 5-93.
-CAUTION-
Do not allow programming terminals A4 or
A 6 to become open-circuited while resistance
programming the output current. If they do
open, the supply's output current rises to a
value that may damage the supply or the
load. If in the particular programming con¬
figuration used there is a chance that the
terminals might open, we suggest that a
200 ohm resistor be connected across the
programming terminals. Of course, when this
resistor is used, the resistance value actually
programming the supply is the parallel
combination of the remote programming
resistance and the resistor across the
programming terminals. Like the program¬
ming resistor, this resistor should be a low
noise, low temperature coefficient type.
The load on the programming voltage source is less than 20
microamperes. The programming voltage required to obtain
maximum rated current from these supplies is about 500
millivolts. An input greater than 600mV may damage the
instrument through excessive power dissipation. Impedance
matching resistor R^ is required to maintain the temperature
coefficient and stability specifications of the supply. To
adjust the output current to exactly zero with a zero pro¬
gramming voltage, follow the same instructions as are referred
to in paragraph 3-46.
3-48 Constant Current Output, Voltage Input (Variable
Gain). In the remote programming arrangement shown in
Figure 3-9, the series combination of external voltage
source Eg and reference resistor Rp replaces the supply's
internal current programming source. As a result, the volt¬
age this external current source develops across gain
control Rp becomes the reference against which the voltage
drop across the output current sampling resistor is compared
by the constant-current comparator. The relationship
between Eg and the supply's output current depends on
the resistance ratio Rp/Rp and on the constant-current
programming coefficient (Kp) of the supply. (These
coefficients are given in paragraph 3-47.) The relationship
between input voltage and output current is
iQyy (Eg x Rp)/( K p x Rp).
3-47 Constant Current Output, Voltage Input (Fixed
Gain). The rear panel connections shown in Figure 3-8
allow the output current to be varied by using an external
voltage source to program the supply. The constant-current
programming coefficients for the supplies included in this
manual are as follows (±10%):
Model 6259B 10.OmV/ampere
6260B 5.0mV/ampere
6261B lO.OmV/ampere
6268B 16.7mV/ampere
6269B 10.OmV/ampere
Figure 3-7. Resistance Programming of Output Current
3-49 When using this programming technique, select
a value for Rp that is less than 10k ohms and that would
conduct at least 2.5 milliamps if connected across the
programming voltage source with its voltage at the maximum
value of input voltage to be used. Once the value for Rp
is selected, multiply it by Kp x Iq^j (max)/Eg (max) to
find Rp. (|f desired, the power supply's front panel current
controls can be used in place of external gain control R p
by deleting the external gain control from the circuit and
strapping together terminals A5 and A6.)
Figure 3-8. Voltage Programming of Output Current
(Fixed Gain)
3-7

3-50 The output current of the supply can be adjusted
to exactly zero with a zero programming voltage input
either by installing and adjusting R11 5 as discussed in
paragraph 5-92 or, if the instrument is equipped with
Option 021 or 022, by adjusting potentiometer R116 as
discussed in paragraph 5-94
3-51 Auto-Parallel Operation
3-52 Use the rear panel interconnections shown in
Figure 3-10 or 3-11 to auto-parallel two or three supplies.
This mode of operation provides a greater current capacity
than can be obtained from a single supply while maintain¬
ing nearly equal load sharing among the paralleled supplies
under all load conditions. Supplies having the same model
number make the most practical auto-parallel combinations,
but any of the supplies included in this manual that have
equal current ratings may be used.
NOTE
Use wires of equal length and gauge to connect
each auto-paralleled supply to the load. Load
sharing accuracy is affected unless the positive
leads connecting each supply to the load are
all equal in resistance.
3-53 Setting the Voltage and Current Controls. The
auto-parallel combination of two or three supplies behaves
as if it were a single constant-voltage/constant-current
supply controlled by the voltage and current controls of
the master supply. The voltage controls of the slave(s)
are disabled, but their current controls remain operative
and must be set to maximum to prevent a slave supply from
independently reverting to constant current operation as
would occur if the output current setting of the master
supply exceeded that of a slave.
EXT.
CROWBAR
TRIGGER
Figure 3-9. Voltage Programming of Output Current
(Variable Gain)
3-54 Overvoltage Protection in Auto-Parallel. The
interconnections shown in Figures 3-10 and 3-11 between
the external crowbar trigger terminals on the master and on
the slave(s) must be made to permit the overvoltage crowbar
in the master to fire the SCRs in the master and the slave(s)
if an overvoltage condition occurs. Be sure to connect them
with correct polarity, plus to plus and minus to minus. Set
the slave supply overvoltage potentiometer(s) to maximum
(clockwise) to disable them, and adjust the overvoltage trip
point at the master supply.
3-55 Auto-Parallel With Remote Sensing. To combine
auto-parallel operation with remote sensing, connect the
supplies as described above but remove the +S and —S
jumpers from the master supply and connect the +S and
-S terminals directly to the (+) and (-) ends of the load.
Observe the precautions outlined under paragraph 3-27.
3-56 Auto-Parallel With Remote Programming. When
two or three supplies are connected in auto-parallel, their
combined output voltage, current, or both can also be
remotely programmed. Refer to the appropriate sections
of paragraph 3-34 for the additional rear panel connections
required and make these connections to the master supply
only. Observe all precautions outlined in the paragraphs on
remote programming. The simultaneous use of remote
sensing and remote programming is also possible during
auto-parallel operation.
3-57 Auto-Series Operation
EXT
CROWBAR
TRIGGER
Figure 3-10. Auto-Parallel Operation of Two Units
3-8