OPERATING AND SERVICE MANUAL
{HP PART NO. 00467-90003)
MODEL 467A
POWER AMPLIFIER/SUPPLY
SERIALS PREFIXED: 444.
Copyright Hewlett-Packard Company 1965
Р.О. Вох 301, Loveland, Colorado, 80537 U.S. A,
Printed AUG 1969
Model 467A
Section 1
SECTION I
GENERAL
1-1, DESCRIPTION.
1-2, The solid state 467A Power Amplifier/Supply
is a 10 watt peak power amplifier and -20 £o +20 voit
dc power supply. The power amplifier has a wide
bandwidth with low dec drift from de to 1 MHz offering
wide applications wherever a power source is re-
quired. Low distortion (<0, 01%), low drift and 0.3%
gain accuracy are obtained with high quality compo-
nents and muitiple feedback techniques. The gain of
the amplifier may be varied between one and ten by
a front panel switch which provides fixed gain steps
accurate to +0.3%, A variable gain control enables
the user to set the gain anywhere between zero and
ten witha resolution of better than 0.1% of full output.
Table 1-1 gives the specifications for the 467A Power
Amplifier/Supply.
1-3. QUTPUT CAPABILITY.
1-4. An output greater than 20 volts peak and 0.5
ampere peak is available from dc up to 1 MHz. The
amplifier is protected at all times from short cir-
cuits. The input circuit of the 467A is protected
against damage from voltages up to 200 volts p-p,
INFORMATION
Input and output connectors are provided at the front
and rear of the instrument. The amplifier is a three
terminal device isolated from chassis and may be
floated up to 200 volts dc above chassis ground.
1-5, POWER SUPPLY.
1-06. A front panel switch converts the amplifier to
a power supply that delivers +20 volts de at currents
up to 0.5 ampere. The output level is controlled
by a potentiometer which permits voltages to be set
with resolution of 0,1% of full scale. Full scale
ranges of £1,+2,+4, +10, and £20 volis are selected
by the front panel range switch.
1-7. INSTRUMENT IDENTIFICATION.
1-8. Hewlett-Packarduses a two-section eight-digit
serial number (000-00000). If the first three digits
of the serial number on your instrument do not agree
with those on the title page of this manual, change
sheets supplied withthe manual will define differences
between your instrument andthe Mode! 467A described
in this manual.
il
Mode! 467A
Section II
SECTION II
INSTALLATION
2-1. INSPECTION.
2-2. Upon receipt, unpack and inspect the instrument
for mechanical and electrical damage. Mechanical
inspection includes visually checking the instrument
for scratched and warped surfaces, damaged control
knobs, switches, and indicators, and signs of weather
exposure, The electrical inspection involves checking
instrument operationagainst specification values given
in Table 1-1, Refer to Paragraph 5-5,
NOTE
in case of mechanical damage,
file a claim with the carrier im-
mediately. Tf an electrical mai-
function occurs, refer to the war-
ranty page in the front of this
manual,
2-3. INSTALLATION.
2-4. The Model 467A is a submodular unit that can
be mounted on a bench, or in a rack or cabinet. It is
shipped with plastic feet and tilt stand in place, ready
for bench use. When used as a single submodule, it
is utilized as a bench unit only. When used in com-
bination with other submodule units, a rack adapter
frame or combining case is available for rack or
cabinet mounting. The instrument should be installed
where ambient temperature does not exceed 50°C
(12295. |
2-5. POWER REQUIREMENTS.
2-6. The Model 467A can be operated from a 115 or
230 ac volt £10 source at 50 to 400. Hz, Power con-
nections are made by plugging the power cable (sup-
plied with the instrument) into the AC POWER male
connector at the rear of the unit and the appropriate
power receptacle. An 0.8 ampere slow-blow fuse
is used for 115 and 230 volt operation.
ÉCAUTIONS
BEFORE PLUGGING POWER
CABLEINTO THE RECEPTACLE,
DETERMINE THAT THE LINE
VOLTAGE SWITCH ON THE REAR
PANEL IS SET PROPERLY TO
ACCEPT THAT VOLTAGE (115
OR 230).
2-7. THREE-CONDUCTOR POWER CABLE.
2-8. All Hewlett-Packard instruments are equipped
with a three-conductor power cable, which complies
with the recommendations of the National Electrical
Manufacturer's Association (NEMA) for rack and
cabinet grounding, The offset pin on the cable is the
ground connector.
NOTE
When operating from a two-con-
tactoutlet, the grounding feature
canbe maintained by using a three-
pronged adapter and connecting
the green pigtail on the adapter
to ground.
2-9. REPACKAGING FOR SHIPMENT.
2-10. Thefollowing paragraphs contain a general guide
for repackaging of the instrument for shipment. Re-
fer to Paragraph 2-11 if the original container is to
be used; 2-12 if it is not. If you have any questions,
contact your local -hp- Sales and Service Office. (See
Appendix B for office locations.)
NOTE
if the instrument is to be shipped
to Hewlett-Packard for service
or repair, attach a tag to the in-
strument identifying the owner
and indicating the service or repair
to be accomplished: include the
model number and full serial
number of the instrument. In
any correspondence, identify the
Instrument by model number,
serial number, and serial number
prefix,
2-11. If original container is to be used, proceed as
follows:
a. Place instrument in original container if avail-
able. H original container is not available,
one canbe purchased from your nearest -hp-
Sales and Service Office.
b. Ensure that container is well sealed with
strong tape or metal bands.
2-12. If original container is not to be used, proceed
as follows:
a. Wrap instrument in heavy paper or plastic
before placing in an inner container.
b. Place packing material around all sides of
instrument and protect panel face with card-
board strips.
¢. Place instrument and inner container in a
heavy carton or wooden box and seal with
strong tape or metal bands.
d. Mark shipping container with "DELICATE
INSTRUMENT, " "FRAGILE" etc,
2-1
Model 467A
3-7. AMPLIFIER OPERATING INSTRUCTIONS.
a. Set the AMPLIFIER/SUPPLY control fo the
AMPLIFIER position, selecting the desired
gain setting (VAR., X1, X2, X5, or X10).
b. Set the LINE switch to ON.
NOTE
To assure maximum stability, allow
the instrument to warm up for 30
minutes,
Section III
SECTION 11
OPERATING INSTRUCTIONS
3-1. GENERAL. ¢. Connect DC Voltmeter (-hp- Model 412A) to the
| 467A OUTPUT terminals; adjust the ZERO
3-2. The Model 467A Power Amplifier/Supply canbe control fo obtain a zero de output.
operated as a power amplifier or a power supply.
Controls on the front panel provide: (1) selection of
either operating mode and (2) selection of fixed or d. Connect 467A OUTPUT terminals to the de-
variable amplifier gain and power supply ranges. plied o which the amplified signal is being ap-
3-3. DESCRIPTION OF CONTROLS, |
e. Connect the signal to be amplified to the 467A
3-4, Figure 3-1 gives the description and function INPUT terminals.
of the 467A controls, indicators and connectors,
3-8. POWERSUPPLY OPERATING INSTRUCTIONS.
3-5. OPERATING INSTRUCTIONS.
3-6. Whenoperated as a power amplifier (non-invert- a Connect the 467A OUTPUT terminals to the de-
ing}, the Model 467A has four calibrated gain factors vicetowhich the power supply isbeing applied.
(AMPLIFIER: Xl, X2, X5, and X10) and provides a
maximum output power of 10 watts peak for input fre- b. Set 467A AMPLIFIER/SUPPLY control in the
quencies between de and | MHz. Accuracy of +0.3% SUPPLY range to the desired voltage setting
from dc to 10 kHz ig obtained when operating into a (+1, +2, +4, +10, ог +20).
load of 40 ohms or greater. As apower supply (regu-
lated), the instrument can be operated in five ranges a
of plus or minus output voltages (SUPPLY: +1, +2, с. Set the LINE switch to ON.
+4, +10, and +20). The amplifier gain, or the + de
output can be varied with the VAR. GAIN/VOLTS ADJ. NOTE
control. The input and cuiput terminals are de isolated
from earth ground. Connection of a grounding strap To assure maximum stabilization,
between the power line ground (44) and (4) terminals allow the instrument to warm up
references boththe INPUT and OUTPUT (4) terminals for 30 minutes.
to earth ground.
d. Usingthe VAR. GAIN VOLTS ADJ. control, ad-
just the voltage to the desired level.
NOTE
The VAR, GAIN VOLTS ADJ, con»
trol is used for both coarse and
fine adjustments, Coarse adjust
is made after either limit of the
fine adjust is reached, Full CCW
position produces maximum negative
voltage. FuliCW position produces
maximum positive voltage,
3-1
Section HI
Model 467A
HEWLETT - PACKARD
VOLTS ADJ,
a.
>
бр 467A POWER AMPLIFIER
\
467A-R- 0300 |
LINE ON: switches voitage on; indicator
glows when ac line voitage is ON,
AMPLIFIER/SUPPLY: selects power ampli-
fier or power supply mode of operation for the
instrument.
AMPLIFIER (X1, X2, X5, X10): selects the
fixed step gain factor.
AMPLIFIER (VAR. ): operates in conjunction
with VAR.GAIN to provide variable control of
amplifier gainanywhere between zeroand X10.
SUPPLY: selects full scaleranges of +1, +2,
+4, +10, or £20 volts.
(3) VAR GAIN/VOLTS ADJ.: operates in conjunc-
tion with AMPLIFIER/SUPPLY control to pro-
vide variable control of amplifier gain or selec-
tion of + de output voltage,
VAR GAIN: operates in conjunction with AM-
PLIFIER (selector in VAR, position) to pro-
vide variable control of amptifier gain any-
where between zero and X10,
VOLTS ADJ. : operates in conjunction with
SUPPLY control position to provide variable
control of de output voltage anywhere between
0 volts and +20 volts,
(4) INPUT: banana-type connectors that provide
signal inputand circuit common input connec-
tions for the instrument.
ZERO: a screwdriver adiust that provides com-
pensation for de offset, or unbalance, with no
signal applied to the 467A INPUT terminals.
(6) OUTPUT: banana-type connectors that provide
signal outpubtcircuit commonand chassis outpur
connections for the instrument.
Figure 3-1. Front panel Controls, Indicators and Connectors
E Model 467A
Section HI
15/230V
0.8A
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CN
467A-B8-0098 [”
“
(1) INPUT and OUTPUT connectors; these BNC
connectors are connected in parailel with the
INPUT and OUTPUT terminals on the front
panel.
FUSE: contains a {use which provides protec.
tion for the primary circuit of the instrument
power transformer. This fuse isused for both
115 v and 230 v operation.
Power Connector: accepts a 3-wire power
cable with safety ground,
(4) Line Voltage: atwo-position slide switch; sets
the 467A for 115 or 230 volt operation.
Figure 3-2. Rear Panel Controls and Connectors
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Section IV
Model 467A
Section IV
SECTION IV
THEORY OF
4-1. INTRODUCTION.
4-2. The Model 467A Amplifier circuits include a
high frequency amplifier, a low frequency amplifier,
a two-stage differential amplifier, a driver amplifier,
and two power amplifier stages. These circuits pro-
vide two modes of operation, the power amplifier
mode and the power supply mode,
4-3, Whenthe AMPLIFIER/SUPPLY switch is in the
AMPLIFIER position, the gain canbe set in fixed steps
of X1, X2, X56 and X10, When the switch is in the
AMPLIFIER/ VAR position, the VAR GAIN/ VOLTS
ADJ control can be used to set the amplifier gain to
any value between zero and ten. The input signal is
applied to the attenuator, which selects the gain to be
used by the instrument amplifier circuitry. Ac and
dc feedback stabilize the amplifier gain. Compensation
for de offset, or unbalance, is provided by a ZERO
adjust control on the front panel.
4-4, Whenthe AMPLIFIER/SUPPLY switch is in the
SUPPLY position, the amplifier provides five power
supply voltage ranges: +1, +2, +4, +10 and +20 volts,
variable from plus through zero to minus for each
range, An internal dc reference voltage (plus or
minus) is applied tothe amplifier portion, which pro-
vides a regulated de voltage at the QUTPUT terminals
of the instrument.
4-5. BLOCK DIAGRAM DESCRIPTION.
4-6. Figure 4-1 shows the block diagram for the
467A. The input signal is applied to the high and low
frequency amplifiers. The high frequency amplifier
(Q101) amplifies the ac signal; the low frequency am-
plifier (Q108 through Q110) amplifies the de and low
frequency signals. The amplified input signal is then
applied through the differential amplifier (Q102 and
Q103), amplifier (Q104), and driver amplifier (Q105)
to emitter followers (Q106 and Q107). Power ampli-
fiers Q1 and Q2 (driven by Q106) and Q3 and Q4 (driven
by Q107) provide a balanced signal to the QUTPUT
connectors.
4-7. At frequencies above 1 MHz, negative feedback
from the driver amplifier Q105 is applied to Q191
through C122 and R129 to provide a decrease ín dis»
tortion and remove the power amplifiers from the
feedback loop. Negative feedback from Q105 is applied
to differential amplifiers Q102 and Q103 through R120,
CiibSand R119 to improve frequency response of the
instrument. Gain controlfor highirequencyamplifier
Q101 is supplied from the output of the power amplifiers
(Q1 through Q4) through R148 and R130,
4-8. At frequencies between dc and 50 KHz, negative
feedback from the output provides de gain control and
balance adjust for the low frequency amplifiers Q108
through Q110. ZERO adjust RS provides compensation
for dc unbalance of the signal applied to the low fre-
quency amplifiers. Relay K1 protects the external load
against current surges during turn-on and turn-off.
OPERATION
4-9. SCHEMATIC DIAGRAM DECRIPTION.
4-10. Thefollowing paragraphs give a detailed descrip-
tion of the Model 467A Amplifier circuits. Refer io
Figures 5-13 and5-14, Section Y , {for the schematic
diagrams of the instrument.
4-11. HIGH FREQUENCY AMPLIFIER.
4-12, Trimmer capacitors C301, C303 and C305 can
be adjusted to provide the desired frequency response
characteristics for the instrument. Ac input signals
from the attenuator are applied through C101 to the
high {frequency amplifier Q101. The signal is amplified
by Q101 and coupled through C104 to the base circuit
of Q102. The RC networks, C105, R112, C106 and
R114 are used to improve the frequency response
characteristics of the amplifier @102. The bias volt-
age of Q101 is determined by resistive divider R103
and R104. Ac feedback from power amplifiers (@1,
Q2, Q3, and Q4) is applied through R148 to provide
ac gain adjust for Q101,
4-13. LOW FREQUENCY AMPLIFIER.
4-14. When the AMPLIFIER/SUPPLY selector is in
the SUPPLY position, +7 and -7 volts are supplied
from an internal reference, through resistive dividers,
to the amplifier input. Each SUPPLY position (+1,
+2, +4, +10 and +20) permits setting the de output
voltage to any + value withinthe range selected. The low
frequency amplifier circuit (Q108, Q109 and Q110) am-
plifies the de and low frequency input signal and drives
Qi03. The bias voltage for the low frequency amplifier
is controlled by R132 and R133 and the ZERO control
RS. Transistor Q110 is a current source for the dif-
ferential amplifiers Q108 and Q109. Inductors L101
and L102 control the frequency response of the low
frequency amplifier (at higher frequencies) by causing
degeneration of Q108 and Q108 emitters. High fre-
quencies present at Q109 collector are shorted to
ground by C1098. Low frequency stabilization and over-
all amplifier gain (between de and 50 KHz)are provided
by applying de feedback from the OUTPUT to Q109
base. The ZERO potentiometer R5 provides an adjust-
ment to compensate for dc drift in the instrument.
Varying R35 changes the voltage at Q109 base, thereby
changing the output level of the low frequency ampli-
fier,
4-15. DIFFERENTIAL AMPLIFIER.
4-18. Differential amplifiers Q102 and Q103 provide
an output proportional fo the input signals from the
high frequency amplifier Q101 and the low frequency
amplifier circuit (Q109 and Q110). The high fre-
quency ac signals are coupled to Q102 through C104;
the dc and low frequency signals from the low fre-
quency amplifier are direct-coupled to differential
amplifier Q103. Capacitor C108 bypasses any high
frequency ac from the low frequency amplifier to
4-1
Section IVY
ground. C109 bypasses any high frequency signals
present at the base of Q103. Ac feedback from Q105
collector circuit is applied through C115 to the base
circuit of Q102 for high frequency gain stabilization.
4-17. VOLTAGE AMPLIFIER,
4-18, The voltage amplifier Q104 supplies the majority
of the voltage gain for the instrument. Degeneration
at low frequencies is provided by R127 in the Q104
emitter circuit; C116 provides added phase stability
at high frequencies. Current through R125 provides
the bias current for Q105, Breakdown diode CR104
establishes the proper voltage at QT 04 coliector and
maintains a de sirnal path from Q104 Collector to
Q105 hase.
4-19. DRIVER AMPLIFIER.
4-20. Driver amplifier Q105 is driven by current am-
plifier Q104 and supplies the signal to the power out-
put amplifiers. Transistors Q108 and Q107 are for-
ward biased by diodes CR108 through CR112 and under
no-signal condition are conducting slightly fo reduce
cross-over distortion in the output signal.
4-21. OUTPUT CIRCUITS.
4.22, Transistors Q1 through Qé provide a comple-
mentary symmetry output. Ql and Q2, driven by
emitter follower Q108, provide a low output impedance.
Q3 and Q4, driven by Q107, form a unity gain feed-
back amplifiér. This causes Q3dand Qé foactasa PNP
emitter follower, which is necessary to provide the
complementary symmetry output.
4-23, EXTERNAL LOAD PROTECTION,
4-24. The external! load connected to the 467A is pro»
tected during furn-onand turn-off, from current surges
and voltage transients, by relay K1. The relay con-
tacts openthe circuit tothe OUTPUT connectors when
the relay is de-energized. When the instrument is
turned ON, Ki remains de-energized for about 300
milliseconds. This delay permits the instrument to
stabilize before the output is connected to the load.
The 300 millisecond delay is caused by the RC time
constant of C110 and R161. When the instrument is
turned off, the relay quickly de-energizes and opens
the circuit to the OUTPUT connector.
4-2
Model 467A
POWER SUPPLY CIRCUIT
DESCRIPTION.
4-26, The 467A primary power supply consists of two
regulated power supplies {34 and +34 volts), and five
reference supplies (+7, -7, +15, -15 and +30 volts).
Either 115 or 230 volts ac is connected to the instru-
ment through switch ST and fuse FI to Ti primary.
Switch 82 {slide switch on rear panel) connects T1
primary windings in series for 239 volt operation, or
in parallel for 115 volt operation. The LINE ON lamp
DSi glows when primary power is applied tothe instrg-
ment. |
4-27. MINUS 34 VOLT SUPPLY,
4-28, Transistor @112 in conjunction with R156,
CR129, and CR130 provide a constant current source
which provides base drive for @b and Q6, Q112 also
provides current to keep CR131, CR132, CR133, and
CR135 conducting, R2 and Q5 share the load current
to reduce the dissipation in Q6. For small load
currents Q5 is turned off and resistor RZ supplies the
current, As the load current increases,the base of
Q5 is forward biased and Q5 conducts, sharing the
current, As the load current is increased further,
CR134 is forward biased at a current level determined
by R159. This will reduce the current in CR135 to
zero causing the supply voltage to go to zero also,
4-29, PLUS 34 VOLT SUPPLY.
4-30. The +34 volt supply provides regulated voltage
to the power amplifier circuits. Breakdown diode
CR143 establishes the reference at the base of Q8,
Potentiometer R163 adjusts the current limit setting
for the +34 volt supply.
4-31. REFERENCE SUPPLY.
4-32, The diode regulated reference supply {refer to
Figure 5-14)provides +7, -7, +15 and -15 voltages.
Capacitors C126 and C128 filter the ac voitages.
Breakdown diodes CR146 and CR147 maintain a +15
reference voltage at the junction of R149 and R150.
The series arrangement of diodes CR120 and CR121
(forward biased diodes) and CR122 and CR123 (re-
verse biased diodes) compensates for temperature
and provides a constant -15 reference voltage at the
junction of R151 and R152. The plus and minus 7 volt
reference voltages are obtained in the same manner
as the plus and minus 15 reference voltages, Series
regulator Q111 provides regulated +30 volts to the
positive side of the reference supply.
4-25.
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