HP 722A Service manual

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HEWLETT-PACKARD COMPA Y

01155·1
OPERATING AND SERVICE MANUAL
MODEL 722A/AR
SERIALS PREFIXED: 105-
DC POWER SUPPLY
Copyright HEWLETT.PACKARD COMPANY 1961
1501 PAGE Mill ROAD. PALO ALTO, CALIFORNIA, U.S.A.
P rioted: NOY 1961

Model 722A
TABLE OF CONTENTS
Table of Contents
List of Illustrations and Tables
Section
,Page
VMAINTENANCE
5-1
5-1. Introduction
5-1
5-3. Maintenance Procedures
5-1
5-4.
Dustcover Removal .
5-1
5-6. Zero-Setting the Meter
5-1
5-8.
Printed Circuit Board Removal
5-1
5-10. Test Equipment Required
5-1
5-12.
Performance Check
5-1
5-14.
Troubleshooting
. 5-1
5-15.
Introduction
5-1
5-17.
Trouble Analysis •
5-1
5-20.
Detailed Test Procedure
5-5
5-23.
Reference Voltage Adjustment
5-6
5-25.
Monitoring
5-6
5-27.
Voltage Range
5-6
5-29.
Current Limit
5-6
5-32.
Performance Test
5-6
5-34.
Voltage Range
5-6
5-36.
Current Limiting.
.
5-7
5-38.
Operation Characteristics •
5-7
5-39.
Ripple Characteristics
5-7
5-40.
Load Regulation
5-7
5-41.
Line Regulation
5-8
Section Page
IGENERAL INFORMATION .... 1-1
1-1. Introduction . . . . . 1-1
1-4. Description . . . . . 1-1
1-8. Differences in Equipment . . .. 1-1
1-10. Equipment Supplied . . . . 1-1
1-12. Other Modes of Operation . 1-1
II PREP ARATION FOR USE
2-1
2-1.
Unpackingand Mechanical Inspection
2-1
2-4.
Site Selection and Installation
2-1
2-6.
Line Power
2-1
2-8.
Operation from 230-Volt Supply
2-1
2-11.
Preparation for Storage and Shipment
2-1
2-14.
Storage
2-1
2-16. Incoming Inspection &Perform. Test
2-1
III OPERATING INSTRUcrIONS
3-1
3-1. Operation
3-1
3-3. Current Limiting .
3-1
3-6. Remote Sensing
3-1
IV
PRINCIPLES OF OPERATION
4-1
4-1.
Overall Block Diagram
4-1
4-3.
Rectifyingand Filtering Circuits
4-1
4-6.
Series Regulator
4-2
4-8.
Output Circuit
4-2
4-10. Voltage Regulating Circuit .
4-2
4-14. Current- Power Limiter .
4-2
4-18. Protection Circuits .
4-3
VI REPLACEABLE PARTS
6
-1. Introduction . . .
6-5. Ordering Information . .
6-1
6-1
6-1
01155-1
LIST OF ILLUSTRATIONS
Number Title
1-1. Model 722AR DC Power Supply.
3-1. Operating Controls .........
3-2. Remote Sensing. . .
3-3. Charging Batteries .
3-4. Parallel Operation
4 -1. Simplified Schematic
4-2. Block Diagram. . . .
4-3. Current Power Limiter
5-1. Model 722A Bottom View
5-2. Model 722A Top View
5-3. Servicing Etched Circuit Boards .
5-4. Reference Power Supply (Schematic) .
5-5. Power Supply (Schematic) . . . • . .
LIST OF TABLES
Number Title
1-1. Specifications . . . . • . . .
5-1. Recommended Test Equipment
5-2. Troubleshooting Guide
5-3. Replacement Guide . . . . • . . • .
6-1. Reference Designation Index
6-2. Replaceable Parts ....
Page
1-1
3-0
3-1
3-1
3-1
4-0
4-1
4-3
5-2
5-3
5-4
5-9
5-10
Page
1-0
5-0
5-5
5-5
6-2
6-6
iii

Section I
Table 1-1
Model 722A
Table 1-1. Specifications
RATED OUTPUT: o to 60 volts dc; 0 to 2 amperes dc
LINE REGULATION: Less than 2.5 mv change for ± 10% line voltage change; output set
between 0 to 60 volts
LOAD REGULATION:
Less than 5 mv change at output terminals for 0 to 2 amperes change;
output
set between 0and 60 volts
TRANSIENT RECOVERY TIME: Less than 200 11 sec for recovery within 5 mv for a change from 0 to
full load or full load to 0 at any rated output or line voltage
NOISE AND RIPPLE:
Less than 250 11 v rms
TEMPERATURE STABILITY:
Better than 0.02%j
OC
or 5 mv JOC, whichever is larger
TEMPERATURE RANGE: o
to 550 for operation within specifications
OUTPUT IMPEDANCE: DC:
Less than 2.5 milliohms
AC: Less than 5 milliohms in series with 10 Ilh
OUTPUT METERS: Voltage: 0
to 60 volts, one range
Current: 0 to 2.5 amp, one range
PROTECTION: Output
current limiter continuously adjustable from 100 rna to 2.2 a
COOLING:
Forced air
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722AR
Rack Mount:
DIMENSIONS:
WEIGHT:
Rack Mount: Net 34 lb
POWER: 115
or 230 volts ± 10%, 50 to 60 cps, 40 to 250 watts depending on
line and load conditions
1-0
01155-1

Model 722A
SECTION I
GENERAL INFORMATION
Section I
Paragraphs 1-1 to 1-13
1-1. INTRODUCTION.
1-2. This is an operating and service manual for the
Model 722A DC Power Supply. This manual is appli-
cable only to instruments with the prefix shown on
the front cover except as modified by change sheets.
1-3. Hewlett-Packard instruments use a two-section
eight-digit 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 instrument does not
agree with the identification number shown on the
manual title page, there are differences between the
manual and instrument. These differences are de-
scribed in manual change sheets having the proper
identification number.
1-4. DESCRIPTION.
1-5. The C€tJ Model 722A DC Power Supply is a com-
pletely transistorized, regulated power supply. It
will supply up to 60 volts at 2 amperes with continuous
adjustment of voltage and current limiting. The cur-
rent limit c~n be set at any current between 100 ma
and 2 amperes to protect circuit elements, such as
transistors, under test.
1-6. Two meters measure both current and voltage
drawn by the load continuously so that you may monitor
power supply drain conveniently. The output impedance
is low for both dc and ac so that a minimum of de-
coupling is required in cascaded circuits. Terminals
for remote sensing are provided on the rear of the
chassis so that the ohmic resistance of the supply
leads is minimized.
1-7. The usefulness of the Model 722A is not limited
to transistor applications, but is useful wherever
high stability is required. For instance, Model 722A
is an excellent source for regulating the filament
voltage of vacuum tubes.
1-8. DIFFERENCES IN EQUIPMENT.
1-9. This manual has been written and illustrated for
the Model 722AR (rack-mounted instrument) since this
is the only style of instrument available at the time
of writing. A cabinet-mount model may become avail-
able in the future. This manual will also apply to the
electrical details of the cabinet-mounted model even
though the physical configuration may be different.
1-10. EQUIPMENT SUPPLIED.
1-11. The equipment supplied consists of only the
Model 722A DC Power Supply as this supply is com-
plete in itself.
1-12. OTHER MODES OF OPERATION.
1-13. Two Model 722A's may be connected in series
for greater voltage. Do not connect more than two
722A's in series. Refer to section III for instructions
before attempting to operate these supplies in parallel.
01155-1
Figure 1-1. Model 722AR DC Power Supply
1-1/1-2

Model 722A
SECTION II
PREPARATION FOR USE
Section II
Paragraphs 2-1 to 2-17
,i
2-1. UNPACKING & MECHANICAL INSPECTION.
2-2. Inspect instrument for signs of damage incurred
in shipment. This instrument should be tested as
soon as it is received. If it fails to operate properly,
or is damaged in any way, a claim should be filed
with the carrier. Afull report of the damage should
be obtained by the claim agent, and this report should
be forwarded to us. We will then advise you of the
disposition to be made of the equipment and arrange
for repair or replacement. Include model number
and serial number when referring to this instrument
for any reason.
2-3. Hewlett-Packard Company warrants each in-
strument manufactured by them to be free from defects
in material and workmanship. Our liability under this
warranty is limited to servicing or adjusting any in-
strument returned to the factory for that purpose and
to
replace any defective parts thereof. Any damage
to the instrument upon receipt is due to the carrier.
File a claim with the carrier as instructed in the pre-
ceding paragraph.
2-4. SITE SELECTION AND INSTALLATION.
2-5. The Model 722A should be mounted securely in
a rack. In environments of severe vibration the rear
of the chassis should also be fastened securely. There
should be sufficient space to the rear and along the
sides of the instrument to permit free flow of cool air
for cooling. This instrument will fit any standard
19-inch rack which has a space 5-1/4 inches high. If
the rack is not accessible from the rear, plug the
power cable in before sliding instrument into rack.
Also make any connections to the rear terminal strip.
If the rack is accessible from the rear, these con-
nections may be made at any time. Secure the instru-
ment to the rack with screws and cup-washers. Con-
nect the power cable and connections, if any, to the
rear terminals. Connect the power cable to the power
source.
2-6. LINE POWER.
2-7. The three-conductor power cable supplied with
the instrument is terminated in a polarized, three-
prong male connector recommended by the National
Electrical Manufacturers' Association (NEMA).
WAR ING
The third conductor grounds the instrument
chassis for the PROTECTIO OF OPER-
ATING PERSONNEL. When using a three-
prong to two-prong adapter ground third lead
(green wire) externally.
2-8. OPERATION FROM 230-VOLT SUPPLY.
2-9. This instrument may be used with either a 115-
volt or 230-volt supply with a frequency from 50 to
60
cps, single-phase. This instrument is shipped
01155-1
from the factory ready for operation from a 115-volt
source unless otherwise indicated. Operation from
a 230-volt supply is possible by changing jumper con-
nections or by flipping a switch if the instrument is
equipped with the lIS-volt to 230-volt switch option.
To change the jumpers refer to the schematic for
details (see also figure 5-5).
WAR I G
Remove the power cable from the wall re-
ceptacle before removing the dust cover.
Dangerous potentials are exposed inside the
instrument.
Replace the fuse with the one called out for
230-volt operation in the table of replaceable
parts (section VI).
2-10. If your instrument has the lIS-volt to 230-volt
switch option the input voltage may be changed without
removing the instrument from the rack. First turn
the instrument off or remove the power cable. Then
with a pointed tool, such as the point of a pencil, flip
the lIS-volt to 230-volt switch on the rear apron of
the instrument to 230 volts. Replace the fuse with
the one called out for 230-volt operation in the table
of replaceable parts (section VI).
2-11. PREPARATION FOR STORAGE
AND SHIPMENT.
2-12. The best method of packing the instrument is
in the original shipping carton with the original fillers
packed in the same manner as when received from the
factory. Therefore, when unpacking note carefully
the method of packing and save the original packing
material for possible future re-use.
2-13. If the original packing material is not available
and it is desired to package the instrument for storage
or shipment, first wrap the instrument in heavy kraft
paper to avoid scratching the paint. Then pack in a
cardboard carton with a bursting strength of at least
150 lb per square inch. Pad the instrument on all
sides with at least 2 inches of rubberized hair or at
least 4 inches of tightly packed excelsior.
2-14. STORAGE.
2-15. No special precautions are necessary in storage
except the usual protection against mechanical damage,
salt air, etc.
2-16. INCOMING INSPECTION AND
PERFORMANCE TEST.
2-17. This instrument should be checked as soon as it
is received to determine that its electrical character-
istics have not been damaged in shipment. Refer to
paragraphs 5-32 through 5-41.
2-1

Section III
Figure 3-1
Model 722A
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1. Turn AC POWER switch ON.
2. Adjust COARSE and FINE VOLTAGE
controls until the voltage on the OUTPUT
VOLTAGE
meter is of the desired value.
3. Adjust CURRENT LIMIT control until the pointer indicates a current value some-
what greater than the expected value.
4. Turn DC POWER switch ON.
If the OUTPUT VOLTAGE drops when DC POWER is turned on, the current limit
is probably being exceeded.
Figure 3-1. Operating Controls
3-0
01155-1

Model 722A Section III
Paragraphs 3-1 to 3-11
SECTION III
OPERATING INSTRUCTIONS
3-1. OPERATION.
3-2. Refer to figure 3-1 for a complete illustrated
description of all operating controls. No preliminary
adjustments are necessary before turning on this in-
strument. Connect the wires from the load to the
output terminals either in the front or back of the in-
strument. If these leads are long or run past a source
of interference, twist them if they are open-wire
leads or run a shielded cable. Figure 3-1 explains
step by step how to operate this instrument.
- SENSE
-POWER
SW
FRONT
RL
REAR OR
REAR
SW
+POWER
+SENSE
RO
Figure 3-2. Remote Sensing
722A 1*2
CR CR
- O~----+lII~ ~J----l
J
+0------ RO
722A
722A .. ,
3-10. If the load must be removed with the supply on
be careful where you break the leads going to the load.
Referring to figure 3-2 you may break the circuit at the
point(s) marked SW. Do NOT break the circuit at the
point(s) marked X as the supply will be damaged.
Figure 3-3. Charging Batteries
3-11. If this supply is to be connected to an active
load (one which supplies voltage) further precautions
must be taken. The load must not be allowed to run
current through the supply in the reverse direction.
WHEN CONNECTI GTHIS SUPPLY TO AN ACTIVE
LOAD ALWAYS MAKE SURE THAT THE VOLTAGE
OF THE MODEL 722A SUPPLY IS GREATER THAN
THE VOLTAGE ON THE TERMINALS WHERE THE
SUPPL Y IS TO BE CONNECTED. The recommended
way of protecting the supply is to use diodes. Figures
3-3 and 3-4 illustrate the proper way to connect these
diodes when connecting this supply to a battery or
when connecting two supplies in parallel. These diodes
must be able to carry 2 amperes current and have a
peak inverse voltage greater than 50 volts. A suitable
diode may be ordered from Hewlett-Packard as stock
number 1901-0019.
3-3. CURRENT LIMITING.
3-4. The maximum current delivered by this sup~ly
may be set to any value between 0.1 and 2 amperes.
This will limit the current to the set value and protect
the equipment under test in addition to protecting the
transistors in the Model 722A from dissipating too
much power.
3-5. Occasionally when the current-limit control is
set to maximum current and maximum current is
drawn the instrument will not adjust down later to
a smaiIer current limit. In this case switch the power
switch to OFF-RESET position momentarily and then
back ON. The instrument will now be reset and will
limit at lower levels of current limit.
3-8. To minimize this effect a separate set of termi-
nals for the sensing voltage is provided on the rear
of the instrument. These terminals permit a separate
pair of leads to connect at the load to supply the sens-
ing voltage. These leads carry no load curre~t. but
are actually inside the regulating loopof the amplIfIer.
3-9. To use remote sensing run a separate set of
leads from the load to the supply. These leads do not
need to be as heavy as the supply leads but they must
be protected from hum pick-up. Run either twisted
pair open-wire leads or shielded leads if hum pick-up
is severe. Connect the leads to the terminals marked
REM+ and REM- on the terminal strip on the rear of
the instrument. At the load connect these leads to
the load (see figure 3-2).
3-6. REMOTE SENSING.
3-7. When the Remote-Local switch on the rear of
the instrument is in the Local position the voltage for
regulation control (sensing voltage) is taken off the
output of the supply at the front panel. This is not
always the best point to obtain this voltage because
there is a drop in the supply leads between the load
and the supply.
CAUTION
Be sure to observe polarity when making
these connections. Wrong connections may
damage the supply.
+ o---~~---o+
RO
Figure 3-4. Parallel Operation
01155-1
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