Agilent Technologies HP8648A Service manual

Errata
Title & Document Type:
Manual Part Number:
Revision Date:
HP References in this Manual
This manual may contain references to HP or Hewlett-Packard. Please note that Hewlett-
Packard's former test and measurement, semiconductor products and chemical analysis
businesses are now part of Agilent Technologies. We have made no changes to this
manual copy. The HP XXXX referred to in this document is now the Agilent XXXX.
For example, model number HP8648A is now model number Agilent 8648A.
About this Manual
We’ve added this manual to the Agilent website in an effort to help you support your
product. This manual provides the best information we could find. It may be incomplete
or contain dated information, and the scan quality may not be ideal. If we find a better
copy in the future, we will add it to the Agilent website.
Support for Your Product
Agilent no longer sells or supports this product. You will find any other available
product information on the Agilent Test & Measurement website:
www.tm.agilent.com
Search for the model number of this product, and the resulting product page will guide
you to any available information. Our service centers may be able to perform calibration
if no repair parts are needed, but no other support from Agilent is available.
·· )/ ·· Ag 1ilent: Technoli0g1 : es
6516A DC Power Supply Operating and Service Manual
October 1967
06516-90001

DC POWER SUPPLY
HVB SERIES, MODEL 6516A
SERIAL NUMBER PREFIX 70
Printed: October, 1967
dij; Stock Number: 06516-90001

TABLE OF CONTENTS
Section
Page No. Section
Page No.
I GENERAL INFORMATION
.............. 1-1 IV PRINCIPLES OF OPERATION (Continued)
1-1
Description 1-1
4-24
High Voltage Control and
1-4
Overload Protection
1-1
Doubler Circuits
4-4
1-7
Cooling 1-1
4-28 Protection Circuit
4-5
1-9
Output Terminals 1-1
4-30
Reference Regulator
4-5
1-11
Specifications 1-1
1-13
Options 1-1
V MAINTENANCE.
..................... 5-1
1-15
Accessories 1-1 5-1
Introduction
5-1
1-17
Instrument Identification
1-2 5-3 High Voltage Precautions
5-1
1-20
Ordering Additional Manuals
1-2
5-6
Measurement Techniques
5-1
5-9
Test Equipment Required
5-1
I I INSTALLATION
...................... 2-1 5-11
Performance Test
5-4
2-1
Initial Inspection 2-1
5-14 Rated Output, Meter, and Output
2-3 Mechanical Check 2-1
Controls Accuracy
5-4
2-5
Electrical Check 2-1 5-17
Load Regulation
5-4
2-7 Installation Data
2-1 5-19 Line Regulation
5-5
2-9 Location
2-1 5-21
Ripple and Noise
5-5
2-11
Rack Mounting 2-1
5-35 Transient Recovery Time
5-7
2-15
Input Power Requirements 2-2 5-39
Output Impedance
5-8
2-17
Power Cable
2-2
5-42
Temperature Coefficient
5-9
2-20
Repackaging for Shipment 2-2 5-46
Output Stability
5-9
5-49
Current Limit
5-10
III OPERATING INSTRUCTIONS ........... 3-1 5-51
Troubleshooting
5-10
3-1
Turn-on Check Out Procedure 3-1
5-55
Overall Troubleshooting
3-3 Operation 3-1
Procedure
5-10
3-5
Current Limit Provisions 3-1 5-59
Repair and Replacement
5-15
3-7
Operation of Supply Beyond
5-61
Adjustment and Calibration
5-17
Rated Output 3-1 5-62
Meter Zero
5-17
3-9 Load Connection
3-i
5-64
Meter Accuracy Adjustment
5-17
3-13
Output Capacitance 3-2
5-66
Output Voltage (Programming
3-15
Reverse Current Loading 3-2 Current) Adjustment
5-17
3-17 Reverse Voltage Loading 3-2 5-68
Output Current Limit Adjustment
5-17
5-70 Overvoltage Protection
5-17
IV
PRINCIPLES OF OPERATION ........... 4-1
4-1 Overall Block Diagram VI
REPLACEABLE PARTS ................. 6-1
Discussion 4-2 6-1
Introduction
6-1
4-8
Simplified Schematic Discussion 4-3 6-4 Ordering Information
6-1
4-12 Detailed Circuit Analysis 4-4
Reference Designators
4-13 :;ieries Regulator 4-4 Abbreviations
4-15 Constant Voltage Input Circuit 4-4 Manufacturers
4-20 Driver Amplifier 4-4
6-8
Code List of Manufacturers
6-2
4-22 Current Limit Circuit 4-4 Parts List Table
6-5
ii

Figure
Table
1-1
5-1
5-2
5-3
5-4
1-1 DC Power Supply
TABLE OF CONTENTS (CONTINUED)
LIST OF TABLES
Pege No.
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 ~3
Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
Bias, Reference, and Rectifier Voltages ....... 5-10
Low Output Voltage Troubleshooting .......... 5-12
High Output Voltage Troubleshooting ......... 5-14
LIST OF ILLUSTRATIONS
Page No. Figure
iv
5-3 Line and Load Regulation,
2-1 Rack Mounting, Two Units
2-2 Rack Mounting, One Unit
2-1
2-2
5-4
Test Setup
Ripple and Noise, Test Setup
3-1 Front Panel Controls and Indicators
4-1 Overall Block Diagram
3-1
4-1
5-5
5-6
High Voltage Protection Network
Noise Spikes,
Test Setup
Page No.
5-4
5-5
5-6
5-7
4-2 Simplified Schematic Diagram 4-3 5-7 Transient Recovery Time,
Test Setup 5-8
5-1 High Voltage and Troubleshooting
Location Diagram
5-2 Differential Voltmeter Substitute,
Test Setup
5-2
5-4
5-8
5-9
5-10
i i i
Transient Recovery Time Waveforms
5-8
Output Impedance, Test Setup
5-8
Servicing Printed Wiring Boards
5-16

LINE
,,,:~t1 0•1/0.:r
+
VOLTAGE
Figure 1-1. DC Power Supply, Model 6516A
i V

SECTION I
GENERAL INFORMATION
1-1 DESCRIPTION
1-2 This instrument (Figure 1-1) is an all semi-
conductor high voltage supply suitable for either
bench or relay rack operation. It is a compact,
well-regulated, Constant Voltage/Current Limited
supply that will furnish 3,000 volts at 6 milliamps
or can be adjusted throughout the output voltage
range. It is designed for applications requiring
extreme stability, regulation, and insensitivity to
ambient temperature variations.
1-3 This supply utilizes a series regulated
"piggy-back" circuit technique that consists of
placing a well-regulated low voltage power supply
in series with a less well-regulated supply having
a greater voltage capability. The well-regulated
"piggy-back" supply continuously compensates for
any ripple, load regulation, or line regulation de-
ficiencies of the main power source and adjusts
the voltage across its series regulator so that the
total output voltage remains constant despite dis-
turbances in the main voltage source.
1-4 OVERLOAD PROTECTION
1-5 The voltage thumbwheel switches select the
constant voltage level; an internal potentiometer
selects the current limit level. The supply will
automatically crossover from constant voltage to
current limit operation and vice versa if the output
current or voltage exceeds these preset levels.
Detailed characteristics of the output current lim-
iting are given in Paragraph 3-5.
1-6 The power supply is protected from reverse
voltage (positive voltage applied to negative ter-
minal) by an internal protection diode that shunts
current across the output terminals when this con-
dition exists, clamping the reverse voltage. Pro-
tection from reverse current (current forced into
the power supply in the direction opposite to the
output current) must be provided by preloading the
power supply (Paragraph 3-15). The power supply
cannot accept reverse current without damage.
1-7 COOLING
1-8 Convection cooling is used; no fan is re-
quired. The power supply has no moving parts
except for the meter movement.
1-1
1-9 OUTPUT TERMINALS
1-10 Output power is ava~lable via two UG-931/U
connectors mounted on the front panel of the sup-
ply. Mating connectors (UG-932/U) are supplied
with the unit. The output terminals are isolated
from the chassis and either the positive or the neg-
ative terminal may be connected to the chassis by
shorting the center pin to the case of the applica-
ble UG-931/U connector, or by grounding a wire
from the connector to the chassis. The power sup-
ply is insulated to permit operation up to 1, 000
volts de off ground, i.e. the maximum potential
between either output terminal and ground shall not
exceed 4KVdc.
1-11 SPECIFICATIONS
1-12 Detailed specifications for the power supply
are given in Table 1-1.
1-13 OPTIONS
1-14 Options are factory modifications of a stand-
ard instrument that are requested by the customer.
The following options are available for the instru-
ment covered by this manual. Where necessary,
detailed option information (operation, alignment,
etc.) is included throughout the manual.
Option No. Description
OS S0Hz Input Modification. Factory
18
modification includes the substitution
of 6 0Hz with S 0Hz magnetic compo-
nent as indicated at the end of the
parts list in Section VI. In addition,
the overvoltage protection adjustment
is rechecked, refer to Section V.
230Vac ±10%, Single-Phase Input.
Factory modification includes the in-
stallation of a 230 volt input trans-
former to replace the standard 115 volt
transformers as in die a ted at the rear
of the parts list in Section VI.
1-15 ACCESSORIES
1-16 The accessories listed in the following chart
may be ordered with the power supply or separately

from your local 0j,, sales office. (Refer to list at
rear of manual for addresses.) Additional informa-
tion on accessories is given in Section II.
rffe, Part No,
145 lSA
14525A
Description
Raek Kit for Mounting one 5¼" H
supply in a standard 19" EIA rack.
(Refer to Section II for details.)
Rack Kit for mounting two S¼" H
supplies in a standard 19" EIA rack.
(Refer to Section II for details.)
1-17 INSTRUMENT IDENTIFICATION
1-18 Hewlett-Packard power supplies are identi-
fied by a three-part serial number tag. The first
part is the power supply model number. The sec-
ond part is the serial number prefix, which consists
of a number-letter combination that denotes the
date of a significant design change. The number
1-2
designates the year, and the letter A through L
designates the month, January through December,
respectively. The third part is the power supply
serial number; a different sequential number is as-
signed to each power supply,
1-19 If the serial number prefix on your power
supply does not agree with the prefix on the title
page of this manual, use the change page that is
included to update the manual to the proper serial
number. Where applicable, backdating information
is given in an appendix at the rear of the manua·l.
1-20 ORDERING ADDITIONAL MANUALS
1-21 One manual is shipped with each power sup-
ply. Additional manuals may be purchased from
your local<&, sales office (see list at rear of this
manual for addresses). Specify the model number,
serial number prefix, and 0j,, stock number provided
on the title page.

Table 1-1.
OUTPUT:
0-3000Vdc, 0-6 milliamperes.
INPUT:
llSVac ±10%, single phase, 57-63Hz, lA, 40W.
LOAD REGULATION:
Less than 0.01% or 16mV (whichever is greater)
output voltage change for a full load to no load
change in output current.
LINE REGULATION:
Less than 0.01% or 16mV (whichever is greater)
output voltage change for a 10% change in the
nominal line voltage.
RIPPLE AND NOISE:
Less than 2mVrms, SmV p-p.
TEMPERATURE RANGES:
Operating: 0 to ss
0c.
Storage: -20 to +ss
0c.
TEMPERATURE COEFFICIENT:
Less than 0. 02% +2mV output voltage change
per
0c
after 30 minute warm-up.
STABILITY:
Less than 0. 05% +SmV total drift for 8 hours
after 30 minute warm·-up and with 30c ambient
variation.
OUTPUT IMPEDANCE:
Less than 32 ohms from de to 30Hz.
Less than 8 ohms from 30Hz to l0OkHz.
Less than 2 ohms from lO0kHz to 1MHz.
TRANSIENT RECOVERY TIME:
Less than 100µ seconds is required for output
voltage to recover to within 0.01% or 16mV of the
nominal output voltage following a full load
change in output current. The nominal output
Specifications
1-3
voltage is defined as the mean between the no
load and full load voltage.
OVERLOAD PROTECTION:
An all electronic, continuously acting current
limit protects the power supply for all overloads
regardless of how long imposed, including a di-
rect short circuit across the output terminals.
CONTROLS:
An in-line 4-digit (thumbwheel) voltage program-
mer permits control of the output voltage; resolu-
tion is lV.
METER:
The front panel meter is a 0-35 00V voltmeter.
OUTPUT TERMINALS:
The de output of the supply is floating; thus,
the supply can be used as either a positive or
negative source. Terminals for +OUT, -OUT,
and GND are provided on the front of the supply.
COOLING:
Convection cooling is employed. The supply
has no moving parts.
SIZE:
B½" W x 5¾" H x 16" D. Two of the units can be
mounted side by side in a standard 19" relay rack.
WEIGHT:
17 lbs. net, 20 lbs. shipping.
FINISH:
Light gray front panel with dark gray case.
POWER CORD:
A 3-wire 5-foot power cord is provided with each
unit.

SECTION II
INSTALLATION
2-1 INITIAL INSPECTION
2-2 Before shipment, this instrument was in-
spected 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, proceed as described in the Claim for
Damage in Shipment section of the warranty page
at the rear of this manual.
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 meter is 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 bench
operation. It is necessary only to connect the in-
strument to a source of power and it is ready for
operation.
2-9 LOCATION
2-10 This instrument is air cooled. Sufficient
space should be allotted so that a free flow of
cooling air can reach the sides and rear of the in-
strument when it is in operation. It should be used
in an area where the ambient temperature does not
exceed ssoc.
2-11 RACK MOUNTING
2-12 This instrument may be rack mounted in a
standard 19 inch rack panel either alongside a
similar unit or by itself. Figures 2-1 and 2-2
show how both types of installations are accom-
plished.
- 0
__ ,o
Figure 2-1. Rack Mounting, Two Units
2-1

D HARRISON DC POWER SUPPLY
0 e G
61
HEWLETT PACKARD 0 0
ME~ CURRENTCJ
.--VOLTAGE-.
~~
Q Q
VOLTS AMPS
COARSE FINE
OFF~
(fjJ (J
(J
E::l
+ GNO -
Q G g e
~ '9 " s 0 0 Q
-
Figure 2-2. Rack Mounting, One Unit
2-13 To mount two units side-by-side, proceed
as follows:
a. Remove the four screws from the front
panels of both units.
b. Slide rack mounting ears between the
front panel and case of each unit.
c. Slide combining strip between the front
panels and cases of the two units.
d. After fastening rear portions of units to-
gether using the bolt, nut, and spacer, replace
panel screws.
2-14 To mount a single unit in the rack panel,
proceed as follows:
a. Bolt rack mounting ears, combining
strips, and angle brackets to each side of center
spacing panels. Angle brackets are placed be-
hind combining strips as shown in Figure 2-2.
b. Remove four screws from front panel of
unit.
c. Slide combining strips between front
panel and case of unit.
d. Bolt angle brackets to front sides of case
and replace front panel screws.
2-15 INPUT POWER REQUIREMENTS
2-16 This power supply is operated from a nominal
115 volt 60 Hz power source. The input power re-
quired when operated from a 115 volt 60 Hz power
source at full load is:
Model 6110A 60 Watts
Model 6516A 40 Watts
2-2
2-17 POWER CABLE
2-18 To protect operating personnel, the National
Electrical Manufacturers Association (NEMA) rec-
ommends that the instrument panel and cabinet be
grounded. This instrument is equipped with a
three conductor power cable. The third conductor
is the ground conductor and when the cable is
plugged into an appropriate receptacle, the instru-
ment is grounded. The offset pin on the power
cable three-prong connector is the ground connec-
tion.
2-19 To preserve the protection feature when op-
erating the instrument from a two-contact outlet,
use a three-prong to two-prong adapter and con-
nect the green lead on the adapter to ground.
2-20 REPACKAGING FOR SHIPMENT
2-21 To insure safe shipment of the instrument, it
is recommended that the package designed for the
instrument be used. The original packaging mate-
rial 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. Be sure to attach a
tag to the instrument which specifies the owner,
model number, full serial number, and service re-
quired, or a brief description of the trouble.

SECTION III
OPERATING INSTRUCTIONS
3-1 TURN-ON CHECK OUT PROCEDURE
3-2 The following procedure describes the use of
the front panel controls and indicators illustrated
in Figure 3-1 and insures that the power supply is
operational.
HARRISON DCPOWfR SUPPLY
HEWLETT· PACl<ARO
LINE
PUSM Qt.I/OFF
+
VOLTAGE
METER
VOLTS AMPS
Figure 3-1. Front Panel Controls and Indicators
a. Push ON/OFF switch-indicator (l); indi-
cator should light.
b. Set METER switch (2) to VOLTS position
(6110A only).
c. Adjust voltage thumbwheel switches for
desired output voltage as indicated on meter.
d. Attach a multimeter to the output and set
the voltage decadial control to at least 200 volts.
Check that the current indication on the multimeter
does not exceed 7. SmA.
e. Remove meter and connect load to output
terminals.
3-3 OPERATION
3-4 The power supply can be operated as a single
unit (normal operation) or in parallel. No provi-
sions for remote programming or remote sensing
have been made due to their limited use and in-
sulation problems at 3, 000Vdc. For safety, insure
that the power supply chassis is grounded (either
via power cord or by other means). The operator can
ground either output terminal or operate the power
supply up to l, 000 volts de off ground (floating).
It is not recommended that the power supply be
floated above 300 volts rms at low audio frequen-
cies (less than S00Hz).
3-1
WARNING
Serious injury to personnel can occur if
the power supply chassis is ungrounded.
The warranty is void if the chassis is
ungrounded during operation.
NOTE
This supply emits a ticking sound which
is characteristic of normal operation. It
in no way indicates that the power sup-
ply is malfunctioning.
3-5 CURRENT LIMIT PROVISIONS
3-6 The current limiting feature is designed to
protect the power supply and the load. It is fac-
tory adjusted by selecting resistor R20 so that the
short-circuit output current will not exceed ap-
proximately 8mA.
3-7 OPERATION OF SUPPLY BEYOND RATED OUTPUT
3-8 The shaded area on the front panel meter
face indicates the amount of output voltage that is
available in excess of the normal rated output.
Although the supply can be operated in this shaded
region without being damaged, it cannot be guar-
anteed to meet all its performance specifications.
However, if the line voltage is maintained above
llSVac, the power supply will probably operate
within its specifications.
3-9 LOAD CONNECTION
3-10 Output terminals are provided on the front
panel of the power supply; mating connectors are
UG-932 and cable type is RG-59/U. The positive
or negative output terminal may be grounded by
shorting the center pin and case of the applicable
UG-931/U jack; or both output terminals unground-
ed (floating operation). Floating operation is per-
mitted to 1, 000 volts de off ground; neither output
terminal should exceed 4,000 volts de. The best
ripple-free results are obtained when one output
jack is grounded and the load is connected to the
other output jack by the appropriate cable and con-
nector.
WARNING
To avoid injury to personnel due to arc-
ing, turn off the power supply before
connecting or disconnecting the load
connectors.

3-11 Each load should be connected to the power
supply output terminals using separate pairs of
connecting wires. This will minimize mutual
coupling effects between loads and will retain full
advantage of the low output impedance of the power
supply. Each pair of connecting wires should be
as short as possible to reduce noise pickup. In
addition, a 0. 1 to 1. 0µf capacitor should be con-
nected between one terminal and the chassis, if
the supply is floated off of ground.
3-12 If load considerations require that the output
power distribution terminals be remotely located
from the power supply, then the power supply out-
put terminals should be connected to the remote
distribution terminals via a pair of shielded wires
and each load connected separately to the remote
distribution terminals. A 0. 1 to 1. 0µf capacitor
should be connected across the remote distribution
terminals to reduce high frequency coupling and
noise.
3-13 OUTPUT CAPACITANCE
3-14 An internal capacitor, across the output ter-
minals of the power supply, helps to supply high
current pulses of short duration during constant
voltage operation. Any capacitance added exter-
nally will improve the pulse current capability,
but will decrease the safety provided by the cur-
3-2
rent limiting circuit. A high current pulse may
damage load components before the average output
current is large enough to cause the current limit-
ing circuit to operate.
3-15 REVERSE CURRENT LOADING
3-16 Active loads connected to the power supply
may actually deliver a reverse current to the pow-
er supply during a portion of its operating cycle.
An external source cannot be allowed to pump cur-
rent into the supply without loss of regulation and
possible damage to the output capacitor. To avoid
these effects, it is necessary to preload the sup-
ply with a "dummy" load so that the power supply
delivers current through the entire operating cycle
of the load device.
3-17 REVERSE VOLTAGE LOADING
3-18 A diode is connected across the output ter-
minals. Under normal operating conditions, the
diode is reverse biased (anode connected to neg-
ative terminal). If a reverse voltage is applied to
the output terminals (positive voltage applied to
negative terminal), the diode will conduct, shunt-
ing current across the output terminals and limit-
ing voltage to the forward voltage drop of the
diode. This diode protects the series transistors
and the output electrolytic capacitors.

-
+I2AV
-
+6.2V
REFERENCE REFERENCE
~
-
SUPPLY REGULATOR -9 4V
+S
-r
BIAS
SUPPLY
AC
POWER
INPUT
TRANSFORMER
_j_
PIGGYBACK + SERIES
-SUPPLY -REGULATOR
(2OOV)
--CURRENT
PROTECTION
LIMIT
DIODE l
CR32
l
-~
-
DRIVER AND
..!:;;;._
VOLTAGE
-
ERROR
INPUT
! AMPLIFIER
CIRCUIT
+
Tl
-
,..
HIGH
VOLTAGE
DOUBLER
>-
(O-32KV)
t
A~
INPUT
I
I -
,..
HIGH
>- CONTROL VOLTAGE -
WINDING
CONTROL
CIRCUIT
Figure 4-1. Overall Block Diagram
4-1
~+21V
~-I7.9V
OVEN
CONTROL
CIRCUIT
CURRENT SAMPLING
RESISTOR
. -
'V V
-METER
CIRCUIT
+6.2V
> VOLTAGE
-CONTROL
+s
[},
ATER
+
-
@]
DC
UT
OUTP
-
-

SECTION IV
PRINCIPLES OF OPERATION
4-1 OVERALL BLOCK DIAGRAM DISCUSSION
(Figure 4-1)
4-2 Models 6110A and 6516A, as illustrated in
Figure 4-1, are constant voltage/current limited
power supplies that utilize a "piggy-back" regu-
lator design. This design extends the usefulness
of the series regulating transistors rated for ap-
proximately 30 volts to short-circuit-proof power
supplies rated for 3, 000 volts. The basic tech-
nique consists of placing the well-regulated low-
voltage "piggy-back" supply in series with a less
well-regulated high voltage doubler. Notice,
however, that the amplified error signal from the
voltage input circuit is dependant upon the total
output voltage-not just the output of the "piggy-
back" supply alone. Thus, the well-regulated
"piggy-back" supply continuously compensates
for any ripple, load regulation, or line regulation
deficiencies of the high voltage doubler, and ad-
justs the voltage across the series regulator so
that the total output voltage remains constant
de spite disturbances in the high voltage doubler.
4-3 For purposes of discussion the voltage
values of Model 6110A are used in the following
paragraphs, however, the theory pertains equally
well to both Models 6110A and 6516A. The
"piggy-back" supply develops 200 volts, and the
high voltage doubler supply is capable of provid-
ing a maximum of 3200 volts. With 30 volts nor-
mally dropped across the series regulatoP, the
maximum output of this supply is 3370 volts; 170
volts from the "piggy-back" supply and 3200 volts
from the high voltage doubler. Thus, the series
regulator of the "piggy--back" supply has a voltage
range for accomplishing the dynamic changes nec-
essary to compensate for the variations of the
power source. Short-circuit protection for the
series regulator in the "piggy-back" supply is
provided by the protection diode, which provides a
discharge path from the positive side of the power
supply to the positive side of the high voltage
doubler shunting the short circuit current around
the series regulator. Whenever the load resist-
ance decreases to a value such that +S becomes
greater than -200 volts, the protection diode con-
ducts. This prevents the output terminals of the
"piggy-back" supply from ever reversing polarity,
and the series regulator will never be called upon
to withstand a voltage strain greater than 200 volts
from its own rectifier.
4-4 The ac input line voltage is raised to the
proper level and coupled to the "piggy-back" sup-
4-2
ply. This supply converts the ac input to raw de
which is fed to the positive terminal via the series
regulator and current sampling resistor network.
The regulator, part of the feedback loop, is made
to alter its conduction to maintain a constant out-
put voltage or limit the output current. Voltage
developed across the current sampling resistor is
the input to the current limiting circuit. If the out-
put current that passes through the sampling net-
work exceeds a certain predetermined level, the
current limiting circuit applies a feedback signal
to the series regulator which alters the regulator's
conduction so that the output current does not ex-
ceed the predetermined limit.
4-5 The voltage input circuit obtains its input by
sampling the output voltage of the supply at the
voltage control. Any changes in output voltage are
detected in the constant voltage input circuit, am-
plified by the error amplifier and driver, and ap-
plied to the series regulator in the correct phase
and amplitude to counteract the change in output
voltage. The reference regulator circuit provides
stable reference voltages which are used by the
constant voltage input circuit and the current limi-
ting circuit for comparison purposes.
4-6 The high voltage control circuit monitors the
voltage across the "piggy-back" supply, and alters
the conduction of transformer Tl so that the output
of the high voltage doubler can be varied between
0 and 3.2 kilovolts. For instance, if the high volt-
age control is adjusted for an output voltage in ex-
cess of the voltage supplied by the "piggy-back"
supply, the input to the high voltage control cir-
cuit becomes more negative. The high voltage
control circuit opens the control winding, and all
the energy appearing at the ac input of transformer
Tl is coupled to the secondary which is connected
to the high voltage doubler. The result is that the
output voltage of the high voltage doubler increases.
If the voltage control is adjusted for an output
which is less than the "piggy-back" supply, the
input to the high voltage control circuit becomes
less negative. The control winding of transformer
Tl becomes shorted impeding the transfer of energy
from the ac input to the secondary which is con-
nected to the high voltage doubler. Thus, the out-
put voltage of the high voltage doubler decreases.
4-7 In Model 6ll"OA, an oven houses the temper-
ature sensitive components in the supply to pro-
vide a low temperature coefficient which results
in excellent stability. The oven control circuit
maintains the oven temperature at 65°C.

1. -;IG~B~ - , j,- -;ER~$ - - 7
SUPPLY + I REGULATOR I CURRENT SAMPLING
RESISTOR
T2 l~--l------------ ..... --011
+
j CR29
I I
L_
I
__ J
J'-1-C-lRt>+3-0-'
CR32
+40V
7cl
l:rJ
L __ _
I
I
~
I
I
I
I
I
CR31
R70
------,<CURRENT
LIMIT
I
I
I.__....__,
I
I
,-,-----
I
I
,---- +56V -----7
I..------. I
ICR7
-0.7V
CR40
-0.7 V
I
I
I
I
I HIGH VOLTAGE I
L
-0 7V CONTROL J I
--- _______ ___j
+S
,-----7
I +40V
I -15V I
I
I
I
l
I
I
I
I
l -0.7V
VOLTAGE
CONTROL
I
L l~L~~N~I _J
C24
Figure 4-2. Simplified Schematic Diagram
4-8 SIMPLIFIED SCHEMATIC DISCUSSION
(Figure 4-2)
4-9 The regulating feedback loop, consisting of
the thumbwheel switch assembly (programming re-
sistors), voltage input circuit, driver and error
amplifier, series regulator, and high voltage con-
trol circuit, function continuously to maintain the
output voltage constant during constant voltage
operation and the output current at a safe limit
during current limit operation.
4-10 The voltage input circuit amplifier, Ql6 de-
tects an error voltage that is proportional to the
difference between the voltage across its program-
ming resistors (thumbwheel switch assembly) and
the de output voltage. The error signal is ampli-
4-3
fied by QlO and applied to the series regulator.
The series regulator increases or decreases the
output current as required to maintain a constant
de output voltage that is equal to the programmed
voltage. The high voltage control circuit, trans-
former TL and the high voltage doubler maintain
the voltage across the series regulator within a
limited range. When the voltage across the series
regulator falls below a predetermined level, Ql 7
turns on, forward biasing diodes CR3 and CR4.
SCR's CR? and CR4D begin firing on each cycle,
and the voltage across C27 and C28 decays. When
the voltage across the series regulator rises above
a predetermined !eve 1, Q 17 turns off, reverse
biasing diodes CR3 and CR4. SCR's CR? and CR40
stop firing and the voltage across C27 and C28
-rises.

4-11 The current limit circuit protects the load and
the series regulator against excessive currents. If
the ex_ternal load resistance is decreased to a point
where the load current exceeds the value selected
by resistor R70, the positive voltage on the collec-
tor of Ql0 forward biases CR31. Thus, the collector
of Ql0 is clamped and the output current is main-
tained at a constant safe maximum. Any further
decreases in load resistance cause the output volt-
age to decrease proportionally.
4-12 DETAILED CIRCUIT ANALYSIS (Refer to over-
all schematic a.t rear of manual)
4-13 SERIES REGULATOR
4-14 The series regulator consists of transistor
stage Qll. The regulator serves as a series con-
trol element by altering its conduction so that the
output voltage and current limit is never exceeded.
The conduction of Ql 1 is controlled by the feed-
back voltage obtained from driver Ql 0.
4-15 CONSTANT VOLTAGE INPUT CIRCUIT
4-16 This circuit consists of voltage decade con-
trol R200 through R224 and amplifier Q16.
4-17 The constant voltage input circuit continu-
ously compares a fixed reference voltage with a
portion of the output voltage and, if a difference
exists, produces an error voltage whose amplitude
and phase is proportional to the difference. The
error output is fed back to the series regulator,
through the error and driver amplifiers. The error
voltage changes the conduction of the series reg-
ulator which, in turn, alters the output voltage so
that the difference between the two input voltages
applied to the differential amplifier is reduced to
zero. The above action maintains the output volt-
age constant.
4-18 The base of Ql6 is connected to the junction
of the programming resistors and the current pull-
out resistor, Rl8, through a current limiting resis-
tor Rl 9. Diode CR5 limits voltage excursions on
the base of Ql6. Rl9 limits the current through
the programming resistors under the condition of
rapid voltage turn-down. Capacitors C4 shunts
the programming resistors to increase the high
frequency gain of the amplifier. The programming
current is determined primarily by the reference
voltage and the pull-out resistor, Rl8.
4-19 Negative feedback is coupled from the out-
put to the input of Q16 by network R20 and C20.
This feedback provides high frequency roll-off in
the loop gain to stabilize the feedback loop.
4-4
4-20 DRIVER AMPLIFIER
4-21 The driver amplifier circuit raises the level
of the error signal from the constant voltage input
circuit to a sufficient level to drive the series reg-
ulator.
4-22 CURRENT LIMIT CIRCUIT
4-23 The output current flows through R23 produc-
ing a voltage drop of 1.8 volts for 7 milliamps out-
put current. The positive voltage appearing on
R23 is connected to the emitter of Ql0. When the
output current reaches 7 milliamps diode CR8 is
forward biased and the base of Ql0 is clamped so
that the conduction of QlO is limited. The value
of resistor R70 determines the level at which the
output current will be limited. This value is nor-
mally selected for 7 milliamps output current.
4-24 HIGH VOLTAGE CONTROL AND DOUBLER
CIRCUITS
4-25 This circuit controls the voltage output of
the high voltage doubler as a function of the volt-
age across the series regulator and resistor R54.
When the voltage across the series regulator rises
to a predetermined value, CR39 becomes for..vard
biased and Ql 7 conducts. Diodes CR3 and CR4
are forward biased and on alternate half-cycles
SCR' s CR7 and CR40 fire, shorting the control
winding of transformer Tl. This action decreases
the voltage on the secondary of Tl thus reducing
the charge on capacitors C27 and C28. This, in
turn, reduces the voltage drop across the series
regulator.
4-26 When the voltage drop across the series reg-
ulator decreases to a predetermined amount, diode
CR39 becomes reversed biased and Ql 7 turns off.
This action reverse biases diodes CR3 and CR4 and
the SCR's cease firing on alternate half-cycles.
The output of the high voltage doubler rises until
Ql 7 again begins to conduct.
4-27 Diodes CR3 and CR4 form an OR-gate that
prevents the interaction of SCR' s CR7 and CR40.
For example, when CR7 fires a positive pulse ap-
pears on its gate, back biasing CR3 and preventing
this positive pulse from tripping CR40. Two RF!
filters in the control winding of transformer Tl
prevent spikes from being transferred to the high
voltage doubler and the ac input line. These fil-
ters consist of C29, R61, C26, R74 and 12.
Diode CR39 protects the base of transistor Q7
from the negative output voltage of the "piggy-
back" supply. This voltage can go as far negative
as -215 volts.

4-28 PROTECTION CIRCUIT
4-29 This circuit prevents the high voltage doubler
from exceeding approximately 4kV which might oc-
cur if the feedback loop were to malfunction.
Diodes CR37 and CR38 are connected directly
across the control winding and rectify (monitor)
the voltage across this winding. The rectified
voltage charges capacitor C24, and when it ex-
ceeds a predetermined level, neon tube VR3 fires.
The resulting positive going voltage turns on Ql 7
which in turn shorts the control winding of trans-
former Tl, thus, reducing the output of the high
voltage doubler. Overvoltage control R71 deter-
mines the level at which VR3 will fire and, there-
fore, controls the maximum output voltage of the
high voltage doubler.
4-5
4-30 REFERENCE REGULATOR
4-31 This circuit supplies regulated de bias volt-
ages to the voltage input circuit and +15Vprogram-
ming voltage to the voltage control circuit. Diodes
CR22 through CR25 and capacitor Cl6 rectify and
filter the 43 Vac developed across the secondary
of T2. The 56 Vdc is regulated by transistor Ql2
which is controlled by Ql3 and VRl. The +15V
programming voltage is developed by constant cur-
rent amplifier Ql4-Ql5 which is connected to the
-40V reference voltage. Resistors RSI and R52 are
selected to provide precisely the correct program-
ming current. Procedures for selecting these re-
sistors are included in the adjustment and calibra-
tion paragraphs in Section V, Maintenance.

SECTION V
MAINTENANCE
5-1 INTRODUCTION
5-2 Upon receipt of the power supply, the per-
formance check (Paragraph 5-ll)should be made.
This check is suitable for incoming inspection. If
a fault is detected in the power supply while mak-
ing the performance check or during normal opera-
tion, proceed to the troubleshooting procedures
(Paragraph 5-51). After trouble shooting and repair
(Paragraph 5-59), perform any necessary adjust-
ments and calibrations (Paragraph 5-61). Before
returning the power supply to normal operation,
repeat the performance check to ensure that the
fault has been properly corrected and that no other
faults exist. Before doing any maintenance
checks, turn-on power supply, allow a half-hour
warm-up, and read the general information regard-
ing measurement techniques (Paragraph 5-6).
5-3 HIGH VOLTAGE PRECAUTIONS
5-4 With the supply operating normally and
neither output grounded to the chassis, there are
many high voltage points within the chassis that
are dangerous to personnel. The potentials vary
from several hundred to 3000 volts and are depend-
ent on the setting of the VOLTAGE thumbwheel
switches. Therefore, always observe the follow-
ing caution:
CAUTION
Connect the positive output to ground
(chassis) before removing the covers
to perform maintenance. This reduces
the number of internal points with
dangerous potentials.
5-1
5-5 With the positive terminal connected to
chassis, only the points illustrated in Figure 5-1
are at a high potential with respect to the chassis.
5-6 MEASUREMENT TECHNIQUES
5-7 All measurements given in this manual are
with a negative power supply output (positive ter-
minal grounded to chassis). When measuring per-
formance of the power supply it is important that
the connection to the output terminal does not in-
troduce additional resistance. For voltage meas-
urements, use a T-connector at the negative output
terminal and connect the load to one output of the
T-connector and the measuring device to the other
output of the T-connector. For current measure-
ments, connect a four-terminal current monitoring
resistor in series with the load resistor and con-
nect both to one output of the T-connector. Con-
nect the measuring device across the current mon-
iroring resistor.
5-8 When using an oscilloscope, ground the case
at the same ground point as the grounded terminal
of the power supply. Make certain that the case is
not also grounded by some other means (powercordl.
Connect both oscilloscope input leads to the power
supply ground and check that the oscilloscope is
not exhibiting a ripple or transient due to ground
loops, pick-up or other means.
5-9 TEST EQUIPMENT REQUIRED
5-10 Table 5-1 lists the test equipment required
to perform the various procedures described in
this section.

DANGER
High Voltage, __ -.:,,
:Ii:··
,,· "f'-" '.•
~-: i,~k:
1
.,
1
:
.. J.~~ '
I •,,:!, ... ·
~- .. ,:£"::"
· ... iW
Figure 5-1. High Voltage and Troubleshooting Location Diagram
5-2
C18 (-)
Under
Capacitor

Type
AC Voltmeter
Variable
Voltage
Transformer
Oscilloscope
Differential
Voltmeter
Repetitive
Load Switch
Resistive
Load
Resistor
Multimeter
Capacitor
Resistor
Oscillator
Controlled-
Temperature
Oven
Resistance
Box
Capacitor
Voltage
Divider
Table 5-1. Test Equipment
Required
Characteristics
Accuracy: 2%. Sensitivity: lmV
fu 11 sea le (min. ).
Range: 90-130 volts. Equipped
with voltmeter acurate within
1 volt, 1 "¥:vV rating.
Sensitivity: IO0µV/cm. Differ-
ential Input
Sensitivity: lmV full scale (min.).
Rate: 60-400 Hz, Zµsec rise and
fall time, 250V, lA.
SOOK, 18W
1 Kn, ±1% ZW non-inductive.
Accuracy 1%
S00pfd, S0vdcw
ZOOK, l/2W
5 Hz - 600 kHz. Accuracy: 2%
Output: l0vrms
0-lOOKn. Accuracy: 0. 1% + ln.
Make-before-break contacts.
lµf, 1600wvdc
100: 1, up to 4KV, 0. 01% Accu-
racy
NOTE
Use
Measure AC voltages
Vary and measure AC
input voltage
Measure ripple and
transient response
Measure regulation;
Calibrate meter
Measure transient
Power supply load
Measure impedance
Measure output current
and DC voltages
Measure impedance
Measure impedance
Measure impedance
Measure temperature
stability
M,easure programming
coefficients
Measure ripple and noise
Load regulation. Line
regulation
Recommended
Model
rfij, 403 B
<&, 140 A plus
1400 A Plug-in.
140 2A Plug-in
for spike meas-
urement only.
<&, 3420
See Note
See Figure 5- 7
<&,412A
<&, 200 CD
<&, Model 6931A
Keithley Instru-
ments, Inc.
Model 6601A
A satisfactory substitute for a differential voltmeter is to arrange a refer-
ence voltage source and null detector as shown in Figure 5-2. The refer-
ence voltage source is adjusted so that the voltage difference between the
supply being measured and the reference voltage will have the required re-
solution for the measurement being made. The voltage difference will be a
function of the null detector that is used. Examples of satisfactory null
detectors are:
1
hp 419A null detector, a de coupled oscilloscope utilizing
differential input, or a S0mV meter movement with a 100 division scale.
For the latter, a 2mV change in voltage will result in a meter deflection of
four divisions.
5-3