HP 6960A Service manual

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06960-90002
OPERATING AND SERVICE MANUAL
MODEL 6960A
DC POWER SUPPLY
Serials Prefixed: G 604
Copyright Hewlett· Packard GmbH 1964
7030 Btlblingen, HerrenbergerstraBe
110, W.·Germany
Prinleo 8/87

'i
Model 6960 ATable of Contents
List
af Illustrations and Tables
TABLE OF CONTENTS
Section
Introduction ..
Instrument Identification " "
General Description •• o~." •• "" ••••••• oo".".o,,.
1-1
1-1
1-1
1-1
GENERAL INFORMATION
1-1
1-3
1-5
II
INSTALLATION
.0 .. " ".·.·.·····
2-1
2-1
2-3
2-5
Inspection ..
Power cabIe ,. ..
115 Vor 230 VOperation ..
2-1
2-1 ;~
2-1
Remote Sensing •••••••••.•••.••••••••••••••••
Operating Controls " " ..
Current Limit Control ..
Connections to Load ..
Automatic Parallel Operation ..
Automatic Series Operation ..
Remote Programming .
3-1
3-1
3-1
3-3
3-3
3-3
3-4
3-4
OPERATING INSTRUCTIONS
3-1
3-3
3-5
3-7
3-9
3-11
3-13
III
4-1 Overall Block Diagram .
4-3 Circuit Description ••••••••••••••••••••••••••
IV PRINCIPLES OF OPERATION ...................... 4-1
4-1
4-1
MAINTENANCE •.• ~ .
Introduction
••••••••••••••••••••••••••••••••
General Maintenance Information •••••••••••••
Test Equipment Required •.••••••••••••••••.••.
Performance Tests .
Detailed Test Procedure ..
V
5-1
5-3
5-5
5-7
5-9
5-11 Trouble Shooting
~ .
5-1
5-1
5-1
5-1
5-2
5-5
5-8
Introduction .
Ordering Information •••••••••••••••••••••••••
VI
REPLACEABLE PARTS
6-1
6-4
................................... 6-1
6-1
6-1

Model 6960 A
Number
Table of Contents
List
of Illustrations and Table
LIST OF ILLUSTRATIONS
Measuring line, load .••...•••.•.•••....•.....••...
Operating Controls ••...•...••••••••.••.•.••..•.••.
.
Terminal Connections ••••••••••••••••• 0"0 ••••••••••••
Model 6960A Power Supply
1-1
3-1
3-2
4-2
5-1
Block Diagram
............
....................................
1-1
3-2
3-6
4-1
5-4
5-2
5-3
5-4
5-5
Number
1-1
5-1
5-2
Regulation and Ripple
Measuring AC Internal Impedance ••••••••• ,., •••••••••
Recommended Connections at the Power Supply •••••••••
Jv4todel 6960 Circuit Diagram ••••.••••••••••••••••••••
Servicing Etched Circuit Boards ••..••...•.•...••.....
LIST OF TABLES
Specifications ••••••••••••••••••••••••••••••••••••
Recommended Test Equipment •••••••••••••••••••••••
Trouble Location Chart ••••••••••••••••••••••••••••
5-4
5-5
5-9
5-10
1-0
5-2
5-8
Replaceable Parts ~ • ,.
6-2
6-2
Reference Designator Index ........................
6-2
6-5
APPENDICE
Code List of Manufacturers
Manual Changes
Sales Office Locations

Model 6960 A
REGULATED OUTPUT:
LOAD REGULATION:
LINE REGULATION:
RIPPLE AND NOISE:
TEMPERATURE STABILITY:
TEMPERATURE RANGE:
OUTPUT IMPEDANCE:
RECOVERY TIME:
METER ACCURACY:
OVERLOAD PROTECTION:
OUTPUT TERMINALS:
REMOTE PROGRAMMI
NG:
POWER:
DIMENSIONS:
WEIGHT:
1-0
Specifications
TABLE 1-1
SPECI FICA TlONS
2 ranges switched by push button switch
0-18 V/600 mA: Voltage cantinuously adjustable
from 0-18 V dc.
600 mA over entire valtage range.
0-36V/3OO mAl Voltage continuously adjustable
from 0-36 V dc.
300 mA over entire voltage range.
Less than 5 mV change in output voltage over full
aperat i ng range.
Less than 5 mV change in output voltage for
±10% power line changes.
Less than 150 ;U Vrms •
Less than O. 1 %;0 C.
Ot055
0
C.
Less than 0.02 Qfrom DC to 1 Kc.
Less than 0.5 Qfrom 1 Kc to 50 kc.
Less than 50 fJs after a change
from full 10aCl to no load.
~ 5% of full scole.(METERS ON OPTION 01 ONLY)
Output current I imiter continuously variable
from 80 to 600 mA on 0-18 V range,
40 to 300 mA on 0-36 V range.
Three banana jacks spaced 3/4 inch apart.
Positive and negative terminals are isolated from
chassis. Amaximum of 400 Vmay be
connected
between ground and either output terminal.
About 200
Q/V external resistance applied to
rear-mounted terminals.
110/220 V:: 10%, 50 to 60 cps, 40 watts.
115/230 V±10%, 50 to 60 cps, 40 watts.
6-3/32 inches (155 mm) high, 5-1/8 inches
(130
mm) wide, 11 inches (279 mm) deep.
Shipping 10 Ibs (4.6 kg)

Model 6960 A
1-1 Introduction
SECTION I
GENERAL INFORMATION
Section I
1-2 This is on operoting and service manual far the Madel 6960 A DC Power Supply.
This manual is applicable only to instruments with the prefix number shown on the
title page except as modified by change sheets.
1-3 Instrument Identification
1-4
Hewlett-Packard instruments use a two-section, eight-cligit serial number, that
is, 000-00000. The first three digits are an identification number; the last five
digits are the instrument serial number. If the identification number on the instru-
ment daes not agree with the identification number shown on the manual title page,
there are differences between the manual and instrument. These differences are
described in manuol chonge sheets having the prooer identificotion number.
1-5 General Decription
1-6 The -hp- Model 6960A DC power supply produces a regulated DC voltage conti-
nuously adjustable from 0to 36 Vup to a current of 300 rnA, or from 0to 18 Vup
to a
current of 600 rnA, according to which range has been selected by means of
the front panel push buttons. The supply makes load circuit performance idepencient
of external power supply influences, has very low source impedance and excellent
regulation against change in line and load.
This supply is especially useful as asource of power for transistor circuits because
it features a protective circuit which electronically li;"its the maximvm OUTput
Fig. 1-1 Model 6960A Power Supply
1-1
~i:;;;mmmmmmm:::::::;;;:mmmmmmmm;mmmm;mmm;;m;;m;; mmmmm;;;, ::i::,Fmm;;mmmm;""""""",,, :;""",,,,,''': ""'H':::;:.;;'.::;::;:"m:;;';;';';;';;::"':;;';;;1:::::::::::::""="'"''''''"'''' "","'""",=:::,::":::::"',,,,,,::,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,l!I1Iil

IvIode I6960 ASection 1
current to volues
selected by 0front ponel control. Accidental damaging of
expensive components
by excessive current can thus be reduced to aminimum,
if the
CURRENT LIMIT control is set to a value just above the normal operating
current
of the external circuit. Another important appl ication of the Model 6960A
Power Supply is in electronic test systems where various fixed voltages have to be
produced sequentially with ahigh degree of reproducabil ity. This can be achieved
because the output voltage of th is supply may be programmed by an externally
connected fixed resistor or aseries of same. The output voltage will then be pro-
portional to the value of this resistor; changing the resistor in predetermined
steps will have corresponding effects on the output voltoge.
Both output terminals of the power supply are insulated from chassis ground. Either
terminal may be grounded as high as 400 V from ground. It is therefore possible
to connect anumber of supplies in series to obtain higher voltages than 36 V.
If more current than 600 mA is needed, there is the possibi Iity of operating several
power suppl ies in parallel.
Remote sensing can be used for minimizing the effect of supply lead resistiance
and thus providing an
exactly regulated voltage at the supplied circuit regardless
of lead length.
2-0
.................••.•.. _---

Model 6960A
2-1 Inspection
SECTION
II
INSTALLATION
Section II
2-2 When the Model 6960A is received, inspect it for damage received in transit.
Operate the instrument to make certain that it is functioning satisfactorily. If
damage is evident, follow the procedures outlined in the "CLAIM FOR DAMAGE
IN
SHI PMENT" page of this manual (inside rear cover).
2-3 Power cable
2-4 The three conductor power cable supplied with the instrument is terminated in a
three connector male power plug recommended by the VDE (Verein Deutscher
Elektrotechniker) •
WARNING
The third conductor grounds the instrument cabinet for the
PROTECTION OF OPERATING PERSONNEL. If 0two con-
nector line power receptacle is used, the instrument cabinet
should be grounded externally.
2-5 115 Vor 230 VOperation
,
2-6 The instrument is designed to work from 110, 115 or 220, 230 volts ± 10 %line voltage,
It is shipped from the factory wired for operation from a 110 Vor 220 Vsource, It may be
re-wired for operation
from a 115 Vor 230 Vline by changing connection on transformer
T1 from 4Ato 4and from 2A to 2 (see Figure 5-4), To operate from 220 V(230 V) line,
set the slide switch on the rear panel to 230 V, to operate from 110 V (115 V), set the
slide switch to 115 V, Fuse F1 should be 0.4 Aslow blow for 220 V(230 V) and 0,8 slow
blow for
110 V (115 V),
2-1

Model 6960 A
SECTION III
OPERATING INSTRUCTIONS
Section III
3-1 Operating Controls
Figure
3-1 shows the functions of the front panel controls and terminals and is
self-explanatory.
3-2 To turn the instrument on, push in either of the range buttons, according to the voltage
and current which
is desired. Accidental setting of both buttons, 18 Vand 36 V, will
cause no damage to the unit; in this case the instrument has been switched to the
36 V - 300 mA range. Pushing in the button marked OFF turns the instrument off.
3-3 Current Limit Control
3-4 This knob adjusts the peak current output of the supply. The indication is nominal. To
set the value exactly, remove the load and short the power supply terminals. Adjust the .!i .... m
CURRENT LIMIT control until the meter indicates the required maximum current. #,
If the supply is to be used in an application where the current drown from the
instrument is not essentially unifotm with respect to time, e.g. in pulse type
circuits, then the fast acting character of the current limiting circuit must be
taken into consideration. The average current may be within the supply rating
or below the maximum current set with the CURRENT LIMIT control, but peak
currents moy be high enough to cause the supply to clip. The CURRENT LIMIT
control must, consequently, be set to a value which is greater than the peak
current requirements of the circuit.
The output terminals are connected internally to a 200 juF capacitor which
helps supply high current peaks, provided they are of short duration. Any exter-
nal capacity added will improve the peak current capability, but will decrease
the safety provided by the current Iimit control. High range currents may then
destroy external components before the average current inside the supply ;11'
increases sufficiently to cause the limiting circuit to operate.
3-1

tv\odeI6960A
Section III
CABINET GROUND
METER INDICATES OUTPUT
/CURRENT
/
,
/
RANGE
PrM£~POWER
OFF ON
o
v ,0 ,~ '" mA Zo"l "4c
\' .' I"" I ,\1,1 ,,,I,, '/ " I" WJe
I! -_.: .. ~ 0»:~" ')11-'\ G '. I ~Selects maximum
I ,' rcurrent output
VOLTAGE ADJUST CURRENT LIMIT(mA)
'fo°
o ~a>?') :600
110
I
)~ ~_'-J, CONNECT LOAD
.0 100 TO (+ ) AND (-)
+r--_---,,-, -Hr---- TERMINALS
~@ '@"Eltherterminalmay
~ ~j oe connected to
CJl'ounded cClblnet
~ terminal.
\
L
SETS
MAXIMUM
OUTPUT
VOLTAGE
METER INDICATES OUTPUT
VOLTAGE 7
/
Fig. 3-1 Operating Controls
3-2

Model 6960 A
3-5 Connections to Load
Section III
3-6 The load may be connected to either the front or rear output terminals of the
power supply as shipped from the factory. Sensing of the output voltage is auto-
matically accomplished in both modes of operation.
The user should realize that the specifications describing the electrical characteristics
of the power supply are given for measurements made directly at the
terminals. Long leads between instrument and load deteriorate load regulation,
which can only be maintained within the specifications of the power supply by
using remote sensing as described
later in this section of the manual.
3-7 Automatic Parallel Operation
3-8 Automatic parallel operation as used here is defined as a parallel operation of
two or more power supplies with one unit (the master) acting as acontrol unit
and the additional units (the slaves) acting as controlled units, where each supply
automatically provides an equal share of current. Each Model 6960A can be used
as master or
slave un it.
The connections of the supplies have to be made in accordance with Fig. 3-2 C.
NOTE
All
un its must operate on the same voltage
range (0- 18V or 0-36 V) !
Turn on the master unit first, then the slave units. Each supply will share the load
current and the master unit will automatically limit the voltage and the current
for all units.
Each slave unit sti II maintains its own short circuit protection and should be set
to a
current limit slightly greater than the maximum current set on the master ~i:;'
unit. If the slave unit was set to acurrent limit slightly greater than the master
un it and if the slave un it was turned on first, the equipment under test might
be damaged by excessive
current before the master unit was turned on and took
over the current control.
3-9 Automatic Series Operation
3-10 Two or more supplies may be operated in series to obtain ahigher voltage than
that obtainable from asingle supply. One unit (the master) acts as acontrol
unit, which controls the additional units (the slaves). The master will set the
total output voltage with each unit contributing the same amount of voltage.
Any Model 6960A may be used as master or slave unit.
Connect the output terminals of the units so that the two terminals of the
master are the most negative of all. The arrangements of interunit connections
are shown in Fig. 3-2 bfor two units and in Fig. 3-2 dfor three or more units.
The connection beween -S of the master and A 2, A 3 of the first slave has
to be
done by means of a 10 K 0/0.5 W resistor.
3-3

Model 6960 A
Section III
Prior to turn on set the VOLTAGE ADJUST control on the master unit fully
counterclockwise and the ones on all slave units fully clockwise. Then turn on
all units and adjust the master unit to the desired voltage. If the slave units do
not track the master unit, turn off all instruments and recheck your connec-
tions.
For minimum ripple across connected outputs, add a 5 /uF (or larger) /50 V
electrolytic capacitor from +S to A2 terminals on all slave units. All instru-
ments must be operated on the same range. Dl not connect more than ten
units in series to avoid exceeding the 400V rating from +or - output terminals
to chass is.
3-] 1Remote Programming
3-12
3-13
The output voltage of Model 6960A may be changed by actuating the front
panel VOLTAGE ADJUST con,rol or by chong"'::; ,ll"C '''''0'' or the externa'i
programming
resistor. If anumber of Model 6960A's are connected in series
or parallel, all units can be conrrolled by cho'lgi"9 rt;e programming resistor
attached to the master unit only. Thus the output voltage may be program-
med remotely by using stepping switches to change the value of the external
resistor in accordance with aprogrammed procedure.
The connections on the rear terminal strip, shown in Fig. 3-2 e have only to
be performed on the master unit. Then the output voltage will vary lire~·I,:
with the programming resistor at a rate of approximately 200 O/V, that means,
a 2000 resistor wi II give 1 V output, 0400 0resistor 2V output, etc.
When using a switch to change the programming resistance whi Ie the instru-
ment is on, be sure to use a shorting contact type switch to keep the voltage
of the supply from rising while switching. If the programming circuit is opened,
even momentarily, the voltage from the supply will rise. This switching tran-
sient may damage the circuit under test.
Remote Sensing
When
the rear terminals of the instrument are connected in the normal fashion,
the voltage for regulation control (sensing voltage) is taken from the output of
the supply at the front panel. This is not always the best point to obtain this
voltage, because there may be a voltage drop in the supply leads between the
load and the supply.
To get around this effect, a separate set of terminals for the sensing voltage
(+S and -S) are provided on the rear of the instrument. These terminals permit
a separate pair of leads to connect at the load to supply the sensing voltage.
The leads carry no load current but are inside the regulation loop of the
ampl ifier.
To use remote sensing, run a separate set of leads from the load to the sensing
terminals. These leads do not need to be as heavy as the supply leads but they
must be protected against hum pickup. Run either twisted pair open wire leads
3-4
._-""--
-----------~.~_."""",.,''''''''''''''''''''''''''''''','''''"."" ,, " " " "" "" .. "" , •• ",,,,,,,,,,,,,,,, ",,,,,,,,,,,,,,,,,,,,,,,,,,.,,,,,, .. ,,.,, ,, .. ,,,,,,,,,,,,,,,,,,· .•.•. " •••• m.'

Model 6960 ASection
III
or shielded leads if hum pickup is severe. Connect the leads to the sensing terminals +5
and
-5 on the rear of the instrument. At the load. attach these leads across the load.
Remove the shorting link between (-) and (-5) and (+) and (+5).
CAUTION
Do not operate the instrument with the sensing
leads open. Be sure to observe polarity when
making these connections. Wrong connections
may damage the supply.
If
the instrument is operated in this manner, the maximum output current decreases at a
rate
of approximately 8% per every 100 MQ of resistance in the minus load lead.
3-5
··················"""",,,,,,,,,,,""'''';;m;>;;;;'',,;:;:±:i1!';il

Model 6960 A
Section III
FRONT
REAR
ferh
I
FRONT REAR
A5 - -5 AI 42 A3
+5 +A4 IMASTER
o0
~r-~ 0u00
0
.0.5
- -S AI AZ 43
+5 +
.0.4
LFJJ
,00
ULU
oUo0
o0- -
~t - ~
0
--'
45
U ~ A243 0 +(j
A4
o0o0SLAVE
(a) Normal Operation
( b) Auto - Series Op.ration for 2 Unit.
'::'5 - -5 A A2t.3 +5 + A4 I
o° ° 91.-_0 __ )_0_0_0_0---,9 °SLAVE
F"RONT
C!~\J
CIJ
I
C2J I
REAR
A5 - - 5A. A 2 A 3 +5+ A4
0090 000090
SLAVE
FRONT
lGh
u~
~
REAR
(e) Auto- Parallel Operation for :3 Units
FRONT
0+ -
o0
i0
(d) Auto - Series Operation for 3 Unite
REAR
(e) Remote Programming
Figure 3-2 Terminal Connections
3-6

Model 6960 A
SECTION IV
PRINCIPLES OF OPERATION
4-1 Overall Block Diagram
Section IV
4-2 As shown in Figure 4-1 the power transformer feeds two fullwave rectifiers. The
rectified AC is filtered and controlled by aseries regulator. The two built in
series
regulators can be operated either in series or parallel depending upon the
selected range of the push button switch and are controlled from the error
ampl ifier man itoring the output vol tage of the supply.
The voltage monitoring error amplifier senses any change in the output voltage
compared to areference voltage. The output of the amplifier causes the resistance of
the series regulator to be varied in such away as to keep the output voltage constant.
The programming current, determined by the reference voltage and the series resistor
R
35, flows mainly through the VOLTAGE ADJUST potentiometer R 40. The product of
the programming current and the value of R 40 equals the output voltage.
4-3 Circuit Description
4-4 The schematic diagram (Fig 5-4) shows all details of the circuit. Power trans-
former is shown to consist of three secondary windings of which the upper two
are the main sources of DC power, while the lower supplies the reference and
auxiliary voltage circuit. Rectifier bridges CR 3 to CR 6 and CR 7 to CR 10
are coupled by R 1. Fi Itering is provided by capacitors C2 and C3. Resistors
POWER
LINE
SUPPLY SUPPLY
OUTPU
RECTIFIERS
REGULATORS
>-to
POWER
ERROR
TRANSFORMER
AMPLIFIER
REFERENCE REFERENCE
RECTIFIERS REGULATORS
T
Fig. 4 - 1 Block Diogram
4-1

Model 6960 ASection
IV
,
,R 3 and R 4
allow a current flow through the rectifier bridges even when no output
current is drawn from the instrument. Series regulators Q1and Q2 act as variable
resistors determining output voltage and current. The output current from one regulator
is monitored by the resistor combinations R39 B, R 9 and R 8, while R39 A, R 9 and R10
monitor the current from the other regulator. The voltage drop across these resistors is
applied to the emitter of Q 5. When this potential exceeds a dist inet value determined
by R 39 Aand Band the load current, transistor Q5is caused to clip. From then on
Q5holds the base voltage and hence the emitter voltage of Q1 through CR 13 and
voltage amplifier Q 3, thus preventing any further increase in the load current. Voltage
divider R 5, R 6 adjust the base-emitter voltage of transistor Q2 if the power supply is
driven in the 36 V / 300 mA range. The ammeter (M 1) indicates the output current by
measuring the
voltage across R 22 and the voltmeter M 2 indicates directly the output
voltage of the power supply.
The
voltage error amplifier consists of the two transistors Q7 and Q8 besides Q 3. In
the constant voltage mode changes in the output voltage due to changes in load or line
voltage are amplified and applied to the base of Q1 in such away as to keep the output
voltage constant. R 23 is used to adjust the positive feedback from the collector of Q8
to the base of Q 7. A proper adjustment of this feedback will result in no output voltage
change when the load current is changed from no load to full load. It can even be
adjusted to yield a negative output resistance, i. e., when aload is applied, the output
voltage increases rather than decreases. Normally, this is adjusted to give zero output
resistance and not a negative resistance.
CR 14 and CR
13 are disconnecting diodes. In the constant voltage mode CR 13 is
closed, CR 14 open, so
that the current error amplifier is out of circuit. In the constant
current operation CR 13 will be automatically opened and CR 14 will be closed to isolate
the voltage error amplifier.
The reference supply consists of a complete feedback amplifier, Q4and Q 6. The
reference voltage itself is controlled by zener diodes CR 20 and CR 21, which also
stabilizes
the negative auxiliary voltages. R 41 helps to supply the thermal stability of the
base
potential of transistor Q 5. Manufacturing tolerances of CR 21 are compensated by
factory adjustment of R27 by means of shunt resistor R38. The value of R17 allows
current changes proportional to line voltage changes. These current changes compensate
possible variations of the current through CR 21 with line voltage variation and minimize
changes in
output voltage.
4-2
"'''ii'''''''''''''''=,", _ ..

Madel 6960 A
5-1 Introduction
SECTION V
MAl NTENANCE
Section V
5-2 This section contoins mointenonce and service information for the Model 6960 A
Power Supply. Aperformance check can be made with the instrument in its cabinet
and is agood test as port of prevention maintenance and incoming quality control
inspection.
5-3 General
Maintenance Information
...
5-4 The power supply has no parts which have a definite limited life. The instrument
should operate indefinitely with no routine maintenance. If any parts are replaced
you should recheck the settings of R 7, R 10 {maximum short circuit current}, R23
{load regulation} and, if necessary, R20 and R 21 {meter adjusts}. Variations
among ports may make it necessary to readjust the controls slightly. Reseal the
controls with adhesive or point after adjustment, otherwise the setting will change
with shock and
vibration.
Alist of possible troubles and the probable cause are tabulated in poragraph 5-12.
In each case curing the trouble involves replacing the defective parts. Be careful
when soldering on the etched circuit board. You can couse damage by excessive
heat or improper technique.
l!
5-5 Test Equipment Required
5-6
5-1
Test equipment required to test this instrument is listed in table 5-1. The necessary
specifications required to obtain reliable test results are listed so that other equip-
ment with equivalent specifications may be used. I
I
I
I
~~~~~_. _.... __ ••....•................................•.............

Model 6960 ASection V
Tobie
5-1
Recommended Test Equipment
Instrument Type Required
Characteristics
Use Instrument
Recommended
AC Voltmeter Accuracy ±3%Measure
ripple I!jJ Model403B
Floating input
DC Volt-Ammeter
Accuracy ±I% Voltage
Measure voltage
I!jJ Model 412A
±2%Current
and current
Oscillator
100 Hz to 100 kHz Measure internal
I!jJ
Model200C
Distortion 0.5 %impedance
or
I!jJ
Model202C
'8
Variable Trans- Mon itormeter Change AC input Any
available
former 1
volt resolution
voltage variable
and 1% accuracy
transformer
with monitoring
meter
Lood Resistor Vorioble Resistor Load for
mea-
Any resistor or
150050W
suring ripple,
combination of
regulation etc.
fixed resistors
Differential 10 mV-range Measure load
I!jJ Madel 740A
Voltmeter necessary
and line
regulatian
5-7 Performance Test
5-8 Before attempting to trouble shoot this instrument make sure the fault is with the
instrument and not with the associated circuit under test. The performance test wi II
enable you to determine this without having to remove this instrument from the ca-
binet. Be sure to perform this test before disturbing any ot the internal adjustments
of the instrument. This test moy also be used as an incoming inspection test to make
sure the instrument has not been damaged
in shipment, for periodic maintenance or
to
check operation of the instrument after repairs.
a) Voltage Range.
An external DC-Voltmeter having an accuracy of 1%or better, i.g. the I!jJ Mo-
del 412A, is connected across the output terminals. The Model 6960A under test
is to be operated in the 36V-300 mA range. Turn the VOLTAGE ADJUST clock-
wise until the 412A indicates 36V output. The knob must have been turned more
than 180 degrees•
Turn the VOLTAGE ADJUST fully counterclockwise. Output
voltage should ga through zero to between 2and 100 mV negative.
5-2
""., " " """"".""."""""""."".",,, ""'''''"",,,!I!Hi

Model 6960 A
b) Current Limiting.
Section V
Switch off Model 6960A under test and connect the Model 412A with the cur-
rent range across the output terminals. Turn the CURRENT LIMIT fully clock-
wise. VOLTAGE ADJUST should be in amid range position. Push the buttons
18 V-0.6 A or 36-0.3 A and wait 15 minutes. When the instrument has warmed
up measure the maximum short circuit current in both ranges. The 412A should
read
about 340 rnA in the 36V range and 680 rnA in the 18 V range.
c) Ripple.
Attach the load resistor for 18 V and 0.6 Ato the output terminals and adjust
the output voltage and current to these ratings. Connect the floating input of
AC-Voltmeter 4038 (or equivalent) ungrounded AC-voltmeter to the output ter-
minals. The readout of the 4038 should not exceed 150 ;UV. In the 36 V-0.3 A
range
the same result should appear.
d) Load regulation.
For the connections, refer to block diagram in Figure 5-1. If the load is switch-
ed off ond on the output voltage change in both ranges should not exceed 5mV.
Th\" "internal resistance" of the power supply under test should be positive, that
is, with load off the output voltage should be higher than with load on.
If you lock agood differential voltmeter, take asecond Model 6960A or another
constant voltage source and compare the output voltage changes to the power
supply under test using asensitive
DC-voltmeter like the 1j Model 412A or
ilj Model 425 A.
e) Line regulation.
Take the same connections as in paragraph 5-8d, change the line voltage of the
Model 6960A under test by means of a variable Iine transformer between 198 V
and 242
V. The change in output voltage should not exceed 5mV on both
ranges.
5-3