HP 711A User manual

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POWER
SU PPLY
SERIALS PREfiXED: 002-
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OPERATING AND SERVICING MANUAL
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OPERATING AND SERVICING MANUAL
MODEL 711A
POWER SUPPLY
SERIALS PREFIXED: 002-
Copyright HEWLETT-PACKARD COMPANY 1956
275 PAGE
MILL ROAD, PALO ALTO, CALIFORNIA, U. S. A.
711A004 -3/1-60

)
OUTPUT VOLTAGES
DC Regulated High Voltage:
AC Unregulated:
REGULATION
RIPPLE
METERING
Current Meter:
Voltage Meter:
TERMINALS
OVERLOAD PROTECTION
POWER
SIZE
Cabinet Mount
Rack Mount
WEIGHT
Cabinet Mount:
Rack Mount:
SPECIFICATIONS
o to 500 volts (without switching), 100 rna maximum load.
6.3 volts, 6 amps maximum load; 12.6 volts CT, 3 amps maxi-
mum load
For line voltage 115/230 volts ±10%, less than 0.5% change or
1. 0 volt chang~, whichever is greater; from no load to full load,
change of less than 0.5% or 1. 0 volt (whichever is greater).
Less than 1. 0mv
o to 100 rna; 0 to 10 with push-button
o to +500 volts; 0 to +50 volts with push-button
Either positive or negative dc regulated high voltage terminal may
be grounded
AC line fused. Overload relay prevents dc output from greatly
exceeding current rating of output milliammeter thus protecting
instrument from overload conditions including short circuit output.
115/230 volts ±10%, 50/1000 cps. Approximately 145 watts de-
pending on load and line voltage.
7-3/8 in. wide, 11-1/2 in. high, 14-1/4 in. deep.
19 in. wide, 7in. high, 12-7/8 in. deep behind panel.
Net: 20 lbs., shipping: 26 lbs.
Net: 24 lbs., shipping: 35 lbs.

SECTION I
CONTENTS
GENERAL DESCRIPTION
1 - 1
1 - 2
1 - 3
1 - 4
General Description
Inspection ....
Power Cable. . .
230-Volt Operation
1-1
I - 1
1- 2
I - 2
SECTION II
OPERA TING INSTRUCTIONS
2 - 1
2 - 2
2 - 3
Controls and Terminals .
Operating Procedure
Output Options . . . . .
II -1
11-2
II - 3
SECTION ill
CIRCUIT DESCRIPTION
3 - 1
3 - 2
3 - 3
3 - 4
3 - 5
General Description. . . . . .
Input .
Regulation. .........
Setting of Output Voltage Level.
Overload Relay. . . . . . . .
ill -1
ill -2
ill -2
ill -3
ill -5
SECTION IV MAINTENANCE
4 - 1
4 - 2
4 - 3
4 - 4
4 - 5
4 - 6
4 - 7
4 - 8
4 - 9
4 - 10
General .....
Cover Removal
Tube Replacement
Replacement of Electrolytic Capacitors .
Replacement of Variable Resistors. . .
Replacement of Rectifiers. ......
Meter Zero Adjustment . . . . . . . .
Power Transformer Primary Connections.
Trouble Shooting Chart
Trouble Localization . . . . . . . . . .
IV -1
IV -1
IV -1
IV -2
IV -2
IV - 3
IV -3
IV - 3
IV -4
IV - 6
SECTION V
TABLE OF REPLACEABLE PARTS
5 - 1 Table of Replaceable Parts . . . . . . . . . . . . . . . . . . V - 1

Sect. I Page 1
SECTION I
GENERAL DESCRIPTION
,------------------ CAUTION -------------------,
Dangerous voltages are present at the terminals and within this instrument
)
)
1·1 GENERAL DESCRIPTION
The Model 71lA Power Supply is a general-purpose
low-power d-c and a-c voltage supply particularly
suited to powering experimental setups.
By means of the facilities provided by the Model
711A the following voltages are made available at
the output terminals on the control panel:
Unregulated ac:
6.3 volts, 3 amperes maximum load current
(two supplies) or
6.3 volts, 6 amperes maximum load current
(one supply) or
12.6 volts, 3 amperes maximum load current
(one supply, tapped at 6. 3V).
Regulated dc:
oto 500 volts, continuously variable; maxi-
mum output load current, 100 mao
NOTE: Insulation within the Model 711A permits
operating the d-c output voltage as much as 500 volts
from chassis ground so that two Model 71lA power
supplies may be operated in series to obtain 1000
volts d-c output while each instrument chassis re-
mains at ground potential.
The d-c output of the Model 71lA has high stability;
for line voltage variations within rated limits, the
level of the regulated output will vary less than O. 5%
or 1 volt (whichever is greater), and from no load
to full load the level of the output will vary less than
0.5% or 1 volt (whichever is greater). Ripple will
be less than 0.001 volt.
While the internal impedance of the Model 711A will
vary both with the d-c load current and the frequency
of any reflections from the equipment being powered,
the internal impedance of the Model 711A will be
less than 10 ohms with any load current and at any
frequency up to afew megacycles.
The dc output is continuously monitored by two
meters, a voltmeter and a milliammeter. Alow
and high range are provided for each meter so that
low values of voltage and current may be read accu-
rately.
The power supply is protected from input or out-
put overload by (1) afuse in the line-voltage input
circuit and (2) a relay, in the main positive bus,
which operates at overload current to interrupt con-
duction through the regulator.
1·2 INSPECTION
This instrument was thoroughly tested and inspected
before being shipped, and is ready for use when re-
ceived.
After the instrument is unpacked, it should be in-
spected carefully for damage received in transit.
If any shipping damage is foUId, follow the procedure
outlined in the" Claim for Damage in Shipment"
sheet in this instruction manual.

Sect. I Page 2
1.3 POWER CABLE
The three-conductor power cable supplied with this
instrument is terminated in a polarized three-prong
male connector recommended by the National Elec-
trical Manufacturers' Association. The third contact
is an offset round pin added to a standard two-blade
connector which grounds the instrument
chassis when
used with an appropriate receptacle. To use this
connector with a standard two contact receptacle,
an adapter should be used to connect the NEMA con-
nector to the two-contact
system. When the adapter
is used, the third contact is terminated in a short
lead from the adapter which can then be connected
to the outlet mounting box in order to ground the
instrument chassis.
1·4 230·YOLT OPERATION
This instrument is normally shipped from the
factory with the dual 115 volt primary windings
of
the transformer connected in parallel for oper-
ation from a nominal 115 volt source. If oper-
ation from a nominal 230 volt source is desired,
the windings may easily be reconnected in series.
Refer to the schematic drawing for details.
The power fuse must be changed from a1. 6 am-
pere slow-blow fuse to a 0.8 ampere slow-blow
fuse.

)
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2.1 CONTROLS AND TERMINALS
All controls and terminals except the fuseholder
are mounted on the front panel. The fuseholder is
mounted on the rear plate of the instrument.
Voltmeter -
This sin~le-scale, two-range (0 to 500 volts; 0to
50 volts) voltmeter indicates the voltage level at the
output of the main regulator. With the DC VOLTAGE
switch
at ON, the level of voltage at the DC VOLT-
AGE output terminals is indicated by the voltmeter.
Normally the meter indicates on the 0- to 500-volt
range; with the
50 VOLTS FULL SCALE push-button
switch
depressed, the meter indicates on the 0- to
50-volt range.
Milliammeter -
This single-scale, two-range
(0 to 100 milliamperes;
o to 10 rna) milliammeter indicates the value of the
d-c l.)ad current. Up to 100 rna can flow in the
load circuit without overloading the milliammeter.
Normally the meter indicates on the 0- to 100-ma
range; with the 10 MA FULL SCALE push-button
depressed, the meter indicates on the 0- to 10-ma
range.
50 VOLTS FULL SCALE -
When
operated (depressed), this SPDT push-button
switch opens the high-range series multiplier re-
sistor and inserts the low-range multiplier.
10 MA FULL SCALE -
This push-button switch, which is ccnnected for
DPST operation, controls the proportion of current
diverted by the respective shunts across (1) the
milliammeter and (2) the protective relay in series
with the milliammeter. When the 10 MA FULL
SCALE switch is operated, the protective relay
operates at between 11 and 17 rna to interrupt con-
duction through the regulator and thereby to inter-
rupt the flow of current through the milliammeter.
Sect. II Page 1
SECTION II
OPERATING INSTRUCTIONS
With the switch at normal, the protective relay oper-
ates at between 110 and 170 rna.
D-C VOLTS ADJ.
Acijustment of the regulated d-c voltage to the desired
level is by means of the FINE and COARSE control
mounted unQ'er the D. C. VOLTS ADJ. designation.
The level of voltage obtained at any given setting
of the controls is indicated by the voltmeter, and
the resulting flow of current in the load circuit is
indicated by the milliammeter.
COARSE -
Operation of the COARSE control (1) adjusts the
setting of a I-megohm variable resistor, R11, and
(2) operates two microswitches, SIA and SIB.
a. Variable resistor R11 is part of the voltage
divider in the circuit which controls the level
of the regulated d-c output voltage.
b. The microswitches make connection to various
taps on the power transformer secondary wind-
ing which
furnishes voltage for the main d-c supply
circuit. At the low-voltage position (ccw) of the
COARSE control, the main d-c supply circuit is fed
by
the low-voltage section of the winding. As the
control
is turned cw, the microswitches are actuated
to complete connection to the higher voltage taps.
FINE -
Operation of the FINE control varies the setting of
variable resistor R12. This resistor also is part
of the voltage divider in the circuit which controls
the level of the regulated d-c output voltage.
Indicator Lights -
There are two indicator lights on the ccntrol panel:
AC'VOLTAGE - This red indicator light glows
to indicate that power is applied to the instrument
circuits.

Sect. II Page 2
DC VOLTAGE -
The operating circuit of this in-
dicator light is controlled by the DC VOLTAGE
switch, and the light glows red when the switch is
at ON to indicate that voltage is applied to the DC
VOLTAGE
output terminals.
AC VOLTAGE Switch -
This SPST toggle switch is in the primary circuit
of the power transformer. With the AC VOLTAGE
switch
at ON, line voltage is closed to power trans-
former T1.
DC VOLTAGE Switch -
There is no voltage on the DC VOLTAGE output ter-
minals until the DC VOLTAGE switch is at the ON
position. When operated, this DPST toggle switch:
'(1) connects the positive d-c bus to the DC VOLTAGE
output
terminals and (2) closes the circuit to the DC
VOLTAGE indicator light.
Output Terminals -
Both the AC VOLTAGE and DC VOLTAGE output
terminals are of the binding-post type, will accom-
modate either a banana plug or wire, and are so
arranged that any banana plug with 3/4-inch spacing
may be used.
AC VOLTAGE -
There are two pairs of output terminals associated
with the a-c voltage supply. Depending on how the
terminal connections are made (see paragraph 2-3
below), the Model 71lA may be arranged to supply
the following a-c voltages:
6.3 volts at 3 amperes (two circuits), or
6.3 volts at 6 amperes (one circuit), or
12.6 volts at 3 amperes (one circuit, tapped
at 6.3 V).
DC VOLTAGE -
There is one pair of output terminals for the regu-
lated d-c voltage supply: +and -. The binding-post
nuts for the + and - terminals are insulated. Neither
the + nor the - terminal is connected to the chassis
within the instrument so that the d-c supply may be
operated either above or below ground by appropriate
external connedion to ground.
On the same mounting plate with the + and - termi-
nals is a terminal (G) which is ccnnected to the in-
strument chassis. The G terminal is cmnected to
earth ground when the power-cable connector is
plugged into a grounded female connector.
FUSE -
The fuseholder, which is mounted on the rear plate
of the instrument, contains the time-delay cartridge
fuse which protects the input circuit. Before start-
ing to install anew fuse, check that the power cable
is disconnected from the line. Replacement fuses
must be of the slow-blow type: 1. 6-ampere fuse
for 115-volt operation or a O. 8-ampere fuse for
230-volt operation.
2-2 OPERATING PROCEDURE
Be sure the Model 711A is so placed that nothing
can obstruct the ventilating louvers in the sides of
the cabinet. Safe operating temperatures with the
cabinet depend upon free air flow through the louvers.
a. Before operating the instrument for the first
time, see paragraph 4-7, Meter Zero Adjustment.
b. Check that both the
AC VOLTAGE and DC VOLT-
AGE switches are in the off position. After the
Model 71lA has been plugged into a power source of
specified voltage and frequency, turn the AC VOLT-
AGE switch to ON, and allow a two-minute warmup
period.
NOTE: If the Model 711A is to be operated from a
23Q:Volt
source, check (1) that power transformer
T1 is strapped for 230-volt operation (strapping
options are shown on the schematic diagram), and
(2) that fuse F1 is a O. 8-ampere Slo-Blo fuse. See
paragraph 4-8.
With the DC VOLTAGE switch still in the off position,
connect
the load. For connection arrangements for
the various options, see paragraph 2-3, below.
c. Check that the COARSE control is in its maxi-
mum counterclockwise (low-voltage) position.
Turn the DC VOLTAGE switch to ON.
d.
To obtain the desired level of d-c voltage, ad-
just the COARSE and FINE controls. The volt-
meter indicates the level of the d-c voltage being
supplied to the +and -output terminals. If the level
of the d-c supply is below 50 volts, the voltmeter
may be operated on the 50-volt range by depressing
the 50 VOLTS FULL SCALE push-button during the
voltage adjustment procedure.

)2·3
OUTPUT OPTIONS
A-C Options - (Figure 2-1)
The a-c supply may be arranged for anyone of three
options:
Two 6.3-volt, 3-ampere supplies (Figure 2-1A)
One 6. 3-volt, 6-ampere supply, by connecting the
two 6. 3-volt supplies in parallel (Figure 2-1B)
One 12.6-volt, 3-ampere supply, by connecting the
two 6. 3-volt supplies in series (Figure 2-1C)
Sect. IT Page 3
D-C Options -
Among the operating options for which the d-c voltage
supplyterminationsmay be arranged are the following:
oto 500 volts, positive or negative with respect to
chassis ground.
oto 500 volts, neither side grounded. (It is recom-
mended that the instrument chassis be grounded
whenever both d-c terminals are operated at apoten-
tial above or below ground.)
Up to 1000 volts, by connecting two Model 711A IS
in series.
TO
LOAD
6.3V 6.3 V
3A 3A
EJOI
tAl
TO
LOAD
6.3V 6.3 V
3A 3A
(8)
TO
LOAD
'" "" \"
STR_AP-+-+--, ~r ,~,
(C)
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)
Figure 2-1. Model 71lA Connection Arrangements for A-C Supply Options