HP 467A Service manual
|
OPERATING
AND
SERVICE
MANUAL
(HP
PART
NO.
00467-90003)
MODEL
467A
POWER
AMPLIFIER/SUPPLY
SERIALS
PREFIXED:
444.
`
Copyright
Hewlett-Packard
Company
1965
Р.О.
Box
301,
Loveland, Colorado,
80537
U.S.A.
Printed
AUG
1969
hick
et
eet
ae
Model
467A
Section
I
SECTION
1
GENERAL
INFORMATION
1-1.
DESCRIPTION.
1-2.
The
solid
state
467A
Power
Amplifier/Supply
is
a
10
watt
peak
power
amplifier
and
-20
to
+20
voit
de
power
supply.
The
power
amplifier
has
a
wide
bandwidth
with
low
de
drift
from
de
to
1
MHz
offering
wide
applications
wherever
a
power
source
is
ге-
quired.
Low
distortion
(<0,
01%),
low
drift
and
0.
3%
gain
accuracy
are
obtained
with
high
quality
compo-
nents
and
multiple
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.
OUTPUT
CAPABILITY.
1-4.
An
output
greater
than
20
volts
peak
and
0.5
ampere
peak
is
available
from
ас
up
to
1
MHz.
The
amplifier
is
protected
at
all
times
from
short
cir-
cults.
The
input
circuit
of
the
467A
is
protected
against
damage
from
voltages
up
to
200
volts
р-р.
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
de
above
chassis
ground.
1-5.
POWER
SUPPLY.
1-6.
A
front
panel
switch
converts
the
amplifier
to
a
power
supply
that
delivers
+20
volts
de
at
currents
ир
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,+2,44,
+10,
and+20
volts
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
Model
467A
described
in
this
manual,
1-1
Model
467A
Section
П
SECTION
И
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
operation
against
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.
If
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
30°C
(122°R).
2-5.
POWER
REQUIREMENTS.
2-6.
The
Model
467A
can
be
operated
from
a
115
or
230
ac
volt
410%
source
at
50
to
400
Hz.
Power
con-
nections
are
made
by
plugging
the
power
cable
(вир-
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.
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.
АП
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-
tact
outlet,
the
grounding
feature
can
be
maintained
by
using
a
three-
pronged
adapter
and
connecting
the
green
pigtail
on
the
adapter
to
ground.
2-9.
REPACKAGING
FOR
SHIPMENT.
2-10.
The
following
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
В
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:
а.
Place
instrument
іп
original
container
if
avail-
able.
If
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.
с.
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,
2-3
Model
467A
SECTION
INSTRUCTIONS
OPERATING
3-1.
GENERAL.
3-2.
The
Model
467A
Power
Amplifier/Supply
canbe
operated
as
a
power
amplifier
or
a
power
supply.
Controls
оп
the
front
panel
provide:
(1}
selection
of
either
operating
mode
and
(2)
selection
of
fixed
or
variable
amplifier
gain
and
power
supply
ranges.
3-3.
DESCRIPTION
OF
CONTROLS.
3-4,
Figure
3-1
gives
the
description
and
function
of
the
467A
controls,
indicators
and
connectors,
3-5.
OPERATING
INSTRUCTIONS.
3-6.
When
operated
as
a
power
amplifier
(поп-іпуегі-
ing),
the
Model
467A
has
four
calibrated
gain
factors
(AMPLIFIER:
X1,
X2,
X5,
and
X10)
and
provides
a
maximum
output
power
of
10
watts
peak
for
input
fre-
quencies
between
de
and
1
MHz.
Accuracy
of
+0.3%
from
дс
to
10
kHzis
obtained
when
operating
into
a
load
of
40
ohms
or
greater.
As
a
power
supply
(regu-
lated),
the
instrument
can
be
operated
in
five
ranges
of
plus
or
minus
output
voltages
(SUPPLY:
+1,
+2,
+4,
+10,
and
+20).
The
amplifier
gain,
or
the
+
de
output
can
be
varied
with
the
VAR.
GAIN/VOLTS
ADJ.
control.
The
input
and
output
terminals
are
de
isolated
from
earth
ground.
Connection
of
a
grounding
strap
between
the
power
line
ground
(-2)
and
(44
terminals
references
both
the
INPUT
and
OUTPUT
(,
terminals
to
earth
ground.
3-7.
AMPLIFIER
OPERATING
INSTRUCTIONS,
a.
Set the
AMPLIFIER/SUPPLY
control
to
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
Ш
с.
Connect
DC
Voltmeter
(-hp-
Model
412A)
to
the
467A
OUTPUT
terminalis;
adjust
the
ZERO
control
to
obtain
a
zero
de
output.
d.
Connect
the
467A
OUTPUT
terminals
tothe
de-
vice
to
which
the
amplified
signal
is
being
ap-
plied.
e.
Connect
the
signal
to
be
amplified
to
the
467A
INPUT
terminals.
3-8.
POWERSUPPLY
OPERATING
INSTRUCTIONS.
a.
Connect
the
467A
OUTPUT
terminals
to
the
de-
vice
towhichthe
power
supply
is
being
applied.
b.
Set
467A
AMPLIFIER/SUPPLY
control
in
the
SUPPLY
range
to
the
desired
voltage
setting
(+1,
+2,
+4,
+10,
or
+20).
c.
Set
the
LINE
switch
to
ON.
NOTE
To
assure
maximum
stabilization,
allow
the
instrument
to
warm
up
for
30
minutes.
4.
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.
Full
CW
position
produces
maximum
positive
voltage,
Section
HI
Model
467A
467A
POWER
AMPLIFIER
HEWLETT:
PACKARD
467А-В-
0900
LINE
ON:
switches
voltage
on;
indicator
glows
when
ac
line
voltage
is
ОМ.
(2)
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
zero
and
X10.
SUPPLY:
selects
full
scale
ranges
of
+1, +2,
+4,
+10,
or
+20
volts.
(3)
VAR
GAIN/VOLTS
ADJ.:
operates
in
conjunc-
3-2
tion
with
AMPLIFIER/SUPPLY
control
to
рго-
vide
variable
control
ofamplifier
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
amplifier
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
inputandcircuit
common
input
connec-
tions
for the
instrument.
ZERO:
a
screwdriver
adjust
that
provides
com-
pensation
for
de
offset,
or
unbalance,
with
no
signal
applied
to
the
467A
INPUT
terminals.
(6)
OUTPUT:
рапапа-іуре
connectors
that
provide
signal
output
circuit
commonand
chassis
output
connections
for
the
instrument.
Figure
3-1.
Front
panel
Controls,
Indicators
and
Connectors
о
wees)
@
н5/230%
0.8A
467А-В-009!
(1)
INPUT
and
OUTPUT
connectors;
these
ВМС
power
transformer.
This
fuse
isusedfor
both
connectors
are
connected
in
parallel
with
the
115
v
and
230
v
operation.
INPUT
and
OUTPUT
terminals
on
the
front
|
в
panel.
©)
Power
Connector:
accepts
a
3-wire
power
cable
with
safety
ground.
FUSE:
contains
a
fuse
which
provides
protec~
(2)
Line
Voltage:
atwo-position
slide
switch;
sets
tion
for
the
primary
circuit
of
the
instrument
the
467A
for
115
or
230
volt
operation.
Figure
3-2.
Rear
Panel
Controls
and
Connectors
Model
467A
Section
Ш
i
i
Н
i
Н
i
р
H
i
Model
467A
>
p
я
о
"чі
чо
©
Ф
[623
J
Ir
Еп
13
MAA
IdAY
шелЗе
Yor
pordung
‘pop
әладүң
Ad—
ччвоо--мияь
xovEdd3
as
—
Hivd
YNYS
SYS
on
ЕЕН
3081909
g
муо
3G
2919
ETAL)
w
“pay
SONY
IVE
Ad+
wovedsad~
опр
амм
{2010'ZD
FO}
6010
‘во
Yald
dy
713343336
AONEANOZed
AO?
YAMOd
{Зо
{$019}
{$0910
‘2010
Mas
td
a
Зла
YATAY
НЕЕ
HOLVANSLLY
О
Ad-—
“р
150)
|
fay
1.
bY
lia]
gy
ge
Bars
чау
лоне
ASNSAO
SH
4
-E
нән
лі+
сно
хэуяаззз
~
+
|
Sais
2210
го
POY
мую
ov
о
ыы
TEES
arie
ое
Model
4674
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,
X5
and
X10,
When
the
switch
is
in
the
AMPLIFIER/VAR
position,
the
VAR
GAIN/VOL
TS
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
de
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
de
reference
voltage
(plus
or
minus)
is
applied
tothe
amplifier
portion,
which
pro-
vides
a
regulated
dc
voltage
at
the
OUTPUT
terminais
of
the
instrument.
4-5.
BLOCK
DIAGRAM
DESCRIPTION.
4-6.
Figure
4-1
shows
the
block
diagram
for the
4674.
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
дс
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
Qi
and
Q2
(driven
by
Q106)
and
Q3
and
Q4
(driven
by
Q107)
provide
a
balanced
signal
to
the
OUTPUT
connectors.
4-7.
At
frequencies
above
1
MHz,
negative
feedback
from
the
driver
amplifier
Q105
is
applied
to
Q101
through
C122
and
R129
to
provide
a
decrease
іп
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,
CiiSand
R119
to
improve
frequency
response
of
the
instrument.
Gain
control
for
high
frequency
amplifier
Q101
is
supplied
from
the
output
of
the
power
amplifiers
(Q1
through
Q4)
through
R148
and
R130,
4-8.
At
frequencies
between
4с
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
R5
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
ODECRIPTION.
4-10.
The
following
paragraphs
give
а
detailed
descrip-
tion
of
the
Model
467A
Amplifier
circuits.
Refer
to
Figures
5-13.and5-14,
Section
V,
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
9101
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
ofthe
amplifier
Q102.
The
bias
volt-
age
of
Q101
is
determined
by
resistive
divider
R103
and
R104.
Ac
feedback
from
power
amplifiers
(Q1,
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
within
the
range
selected.
The
low
frequency
amplifier
circuit
(Q108,
Q109
and
Q110)
am-
plifies
the
de
and
low
frequency
input
signal
and
drives
Q103.
The
bias
voltage
for
the
low
frequency
amplifier
is
controlled
by
R132
and
R133
and
the
ZERO
control
R5.
Transistor
Q110
is
a
current
source
for
the
dif-
ferential
amplifiers
Q108
and
Q109.
Inductors
1101
and
L102
control
the
frequency
response
of
the
low
frequency
amplifier
(at
higher
frequencies)
by
causing
degeneration
of
Q108
and
Q109
emitters.
High
fre-
quencies
present
at
Q109
collector
are
shorted
to
ground
by
C109.
Low
frequency
stabilization
and
over-
allamplifier
gain
(betweende
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
ас
drift
in
the
instrument.
Varying
R5
changes
the
voltage
at
Q109
base,
thereby
changing
the
output
level
of
the
low
frequency
ampli-
fier,
4-15.
DIFFERENTIAL
AMPLIFIER.
4-16,
Differential
amplifiers
Q102
and
Q103
provide
an
output
proportional
to
the
input
signals
from
the
high
frequency
amplifier
9101
and
the
low
frequency
amplifier
circuit
(Q109
and
Q110).
The
high
fre-
quency
ac
signals
are
coupled
to
Q102
through
C104;
the
de
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
IV
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
Q104
collector
and
maintains
a
de
signal
path
from
Q104
Collector
to
Q105
base.
4-20.
Driver
amplifier
Q105
is
driven
by
current
am-
plifier
Q104and
supplies
the
signal
to
the
power
out-
put
amplifiers.
Transistors
Q108
and
Q107
are
for-
ward
biased
by
diodes
CR108
through
CR112and
under
no~signal
condition
are
conducting
slightly
to
reduce
cross-over
distortion
in
the
output
signal.
4-21.
OUTPUT
CIRCUITS.
4-22.
Transistors
Q1
through
Q4
provide
а
comple-
mentary
symmetry
output.
Qİ
and
Q2,
driven
by
emitter
follower
Q106,
providea
low
output
impedance.
Q3
and
Q4,
driven
by
Q107,
forma
unity
gain
feed-
backamplifier.
Thiscauses
Q3and
Q4
toactasa
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
turn-onand
turn-off,
from
current
surges
and
voltage
transients,
by
relay
KI.
The
relay
con-
tacts
open
the
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
4-25.
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
51
and
fuse
Fi
to
Т1
primary.
Switch
52
(slide
switch
on
rear
panel)
connects
Т1
primary
windings
in
series
for
230
voit
operation,
or
in
parallel
for
115
volt
operation.
The
LINE
ON
lamp
DSi
glows
when
primary
power
is
applied
tothe
instru-
ment.
4-27.
MINUS
34
VOLT
SUPPLY.
4-28.
Transistor
Q112
in
conjunction
with
R156,
CR129,
and
CR130
provide
a
constant
current
source
which
provides
base
drive
for
Q5
and
Q6.
Q112
also
provides
current
to
keep
СВ131,
CR132,
CRi33,
and
CR135
conducting.
R2
and
Q5
share
the
load
current
to
reduce
the
dissipation
іп
Q6.
For
small
load
currents
Q5
is
turned
off
and
resistor
R2
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
СВ135
to
zero
causing
the
supply
voitage
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
voltages.
Breakdown
diodes
CR146
and
CR147
maintain
a
+15
reference
voltage
at
the
junction
of
R149
and
R150.
The
series
arrangement
of
diodes
CR120
and
СВ121
(forward
biased
diodes)
and
СВ122
and
CR123
(re-
verse
biased
diodes)
compensates
for
temperature
and
provides
a
constant
-15
reference
voltage
at
the
junction
of
В151
апа
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.
Table of contents
Other HP Amplifier manuals
