Agilent Technologies 300A User manual
Errata
Title & Document Type: 300A Harmonic Wave Analyzer
Manual Part Number: N/A
Revision Date: 11/30/1955
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Hewlett-Packard's former test and measurement, semiconductor products and chemical
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For example, model number HP8648A is now model number Agilent 8648A.
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t
OPERATING
MANUAL
PLUS
SERVICE
MANUAL
MODEL
300A
HARMONIC
WAVE
ANALYZER
This
is
a
combined
Operation,
Instruction,
and
Service
Manual
for
all
~
Mode1300A
Harmonic
Wave
Analyzers.
This
manual
contains
complete
operation
and
servicing
instructions
for
the
300A
and
may
be
used
in
place
of
thl~
Instruction
and
Operating
Manual
originally
supplied
with
each
ins
trument.
Copyright
1956
by
Hewlett-Packard
Company
The
information
contained
in
this
booklet
is
intended
for
the
operation
and
main-
tenance
of
Hewlett-Packard
equipment
and
is
not
to
be
used
otherwise
or
reproduced
without
the
written
consent
of
the
Hewlett-
Packard
Company.
HEWLETT-PACKARD
COMPANY
PAGE
MILL
ROAD,
PALO
ALTO,
CALIFORNIA,
U.S.A.
II
MODEL
300A
HARMONIC
WAVE
ANALYZER
INSTRUCTION
&
OPERATING
MANUAL
TABLE
OF
CONTENTS
SECTION
I
GENERAL
Page
1-1
1-2
GENERAL
DESCRIPTION
SPECIFICATIONS
• • • · . . . · . · .
· .
III
III
SECTION
II
OPERATING
INSTRUCTIONS
2
-1
23D
VOLT
OPERATION.
·· · ····· · · · •
III
2
-2
CONTROLS
&
TERMINALS
· · · ··· · · · · •
IV
2
-3
OPERATION.
. . . .· · ·· · · · · · · • • · · · · ·
IV
2-4
CALIBRATION
ADJUSTMENT
PROCEDURE.
···• •
IV
2
-5
MEASUREMENT
PROCEDURE.
· · · · · •···
IV
2
-6
MEASUREMENT
PRECAUTIONS.
·· · · · · · · · •V
2-7
SELECTIVITY.
. . .· · · · · · · · · · •V
SECTION
III
CIRCUIT
DESCRIPTION
3-1
GENERAL
••••
·.. . . . .. . . .... . .
SECTION
IV
MAINTENANCE
VI
4-1
CABINET
REMOVAL.
· · · · · ·· · · •· · •··
VII
4-2
TUBE
REPLACEMENT.
··········•·•·•·
VII
4-3
LOCAL
OSCILLATOR
AMPLITUDE
ADJUSTMENT.
•·
VII
4-4
VOLTAGE
REGULATOR
ADJUSTMENT.
· · • • • ·•·•
VII
4-5
HUM
BALANCE
ADJUSTMENT.
· · •·••••••••·
VII
4-6
BALANCED
MODULATOR
ADJUSTMENT.
•· · • • ·
VII
4-7
SELECTIVE
AMPLIFIER
ADJUSTMENT
· · •· · •·
VII
SECTION
V
TABLE
OF
REPLACEABLE
PARTS
5-1
GENERAL.
..... . . . . ... . . . . . .. . . .
VII
THE
ATTACHED
300A-2
SERVICE
MANUAL
HAS
A
SEPA-
RATE
INDEX
APPEARING
ON
PAGE
1.
..
III
INSTRUCTION
&
OPERATING
MANUAL
SECTION
I
GENERAL
1-1
GENERAL
DESCRIPTION
The
Model
300A
Harmonic
Wave
Analyzer
is
a
selective
voltmeter
designed
to
measure
the
individual
components
of
complex
waves.
The
selectivity
can
be
varied
by
means
of
selective
amplifiers
to
measure
either
closely
or
widely
spaced
harmonics.
The
instrument
cover
s
the
audio
spectrum
from
30
to
16,000
cps.
It
has
a
wide
voltage
range
so
that
full
scale
readings
may
be
ob-
tained
from
1
millivolt
to
500
volts
0
The
Model
300A
is
well
adapted
to
the
measurement
of
the
harmonic
distortion
in
audio
frequency
equipment
of
all
kinds,
broadcast
receivers,
transmitters;
to
determine
the
harmonic
components
in
ac
machinery
and
power
systems;
to
the
study
of
induced
voltages
on
telephone
lines;
and
to
measurement
of
hum
components
in
rectifier
circuits.
Other
uses
include
the
study
of
noise
by
integrating
portions
of
the
spectrum
with
the
selectivity
control
adjusted
for
a
wide
pass
band
and
the
checking
of
wave
filter
characteristics
with
maximum
selectivity.
The
Model
300A
is
also
useful
as
a
device
to
measure
the
amount
of
cross
or
intermodulation
products
generated
by
the
simultaneous
transmis
sion
of
two
frequencies
by
an
audio
system
or
to
measure
demodulation
of
a
modulated
wave
applied
through
an
audio
system.
1
-2
SPECIFICATIONS
Complete
specifications
for
the
cEiJ
Model
300A
Harmonic
Wave
Analyzer
will
be
found
on
page
3
of
the
cEiJ
No.
300A-2
Service
Manual.
SECTION
II
OPERATING
INSTRUCTIONS
2-1
230
VOLT
OPERATION
This
instrument
is
shipped
from
the
factory
with
the
power
transformer
pri-
maries
connected
in
parallel
for
operation
from
115
volts.
If
operation
from
a
power
line
of
230
volts
is
desired,
the
power
transformer
primaries
must
be
connected
in
series
as
shown
by
the
"Transformer
Detail"
on
the
schematic
diagram
in
Fig.
3
on
page
39
of
the
No.
300A-2
Service
Manual.
Some
older
instruments
have
a
power
transformer
with
a
single
primary
wind-
ing
for
operation
from
115
volts
only.
The
1.
25
ampere
slo-blo
fuse
required
for
115
volt
operation
must
be
replaced
by
a
0.6
ampere
slo-blo
fuse
after
changing
primary
connections
from
parallel
to
series
for
operation
from
230
vo.lts.
IV
2-2
CONTROLS
AND
TERMINALS
All
controls
and
terminals
are
fully
des
cribed
on
pages
4
and
5
of
the
r5j:;
No.
300A-2
Service
ManuaL
CAUTION
THIS
INSTRUMENT
IS
ACCURATE
AT
AMBIENT
TEMPERATURES
OF
APPROXIMATELY
55
TO
95
DEGREES
FAHRENHEIT.
OTHER
AMBI-
ENT
TEMPERATURES
MAY
NECESSITATE
REALIGNMENT
OF
THE
SELECTIVE
AMPLIFIER
SYSTEM.
2-3
OPERATION
The
operation
of
the
Model
300A
is
divided
into
two
parts.
the
calibration
adjustment
procedure
and
the
measurement
procedure.
2-4
CALIBRATION
ADJUSTMENT
PROCEDURE
This
procedure
will
be
found
under
the
heading
of
CALIBRATION
PROCE-
DURE
starting
on
page
11
of
the
r5j:;
No.
300A-2
Service
Manual.
See
the
important
operating
precautions
given
in
step
26
of
CALIBRA
TION
PROCEDURE
in
the
No.
300A-2
manual.
2-5
MEASUREMENT
PROCEDURE
The
instrument
must
be
calibrated
before
attempting
a
measurement.
In
the
following
procedure,
the
voltage
being
analyzed
has
a
fundamental
frequency
of
80
cps
and
an
amplitude
of
20
volts.
The
frequency
and
amplitude
of
this
hypothetical
voltage
have
been
as
sumed
to
simplify
the
instructions.
Any
voltage
between
1
millivolt
and
500
volts
at
any
frequency
between
30
to
16,
000
cps
could
be
similarly
measured.
A
harmonic
frequency
must
not
be
higher
'than
16.
000
cps
if
the
particular
harmonic
voltage
is
to
be
measured.
a.
Calibrate
the
300A
as
previously
described.
b.
Set
the
METER
MULTIPLIER
control
to
50
(XIOO)
and
the
SET
TO
100
FOR
VOLT
AGE
MEASUREMENT
control
to
100.
c.
Set
the
HALF
BAND
WIDTH
control
to
30.
See
step
26B
on
page
12
of
No.
300A-2
Service
Manual
regarding
the
degree
of
selectivity
neces-
sary
for
measuring
voltages
of
various
frequencies.
d.
Set
the
frequency
dial
to
80
cps
and
peak
the
meter
indication
by
adjust-
ing
the
FINE
TUNING
control.
The
METER
SENSITIVITY
control
should
be
adjusted
to
give
a
readable
indication
on
the
millivoltmeter.
The
in-
strument
is
now
tuned
to
measure
the
amplitude
of
the
fundamental
fre-
quency
(80
cps)
with
the
harmonics
excluded.
e.
The
actual
value
of
the
funda'mental
voltage
is
found
by
multiplying
the
millivoltmeter
indication
by
the
multiplying
factor
shown
by
the
position
of
the
METER
MULTIPLIER
control.
J
Example:
METER
SE.
SITIVITY
at
500
(5.
a
on
meter
scale)
full
scale
millivolts.
Meter
pointer
at
2.
a
therefor
e
meter
actually
indicates
200
millivolts.
200
millivolts
x
100
(meter
multiplier
factor)
is
equal
to
20,
000
millivolts
or
20
volts.
2-5
MEASUREMENT
PROCEDURE
(Contld.)
v
..
£.
Turn
the
frequency
dial
to
160
cps
(second
harmonic
of
80
cps)
and
set
the
METER
SEl
SITIVITY
and
METER
MULTIPLIER
controls
to
obtain
a
read-
able
meter
indication.
Use
the
FINE
TUNING
control
to
peak
the
meter
indication.
The
meter
indication
times
the
meter
multiplying
factor
will
give
the
amplitude
of
the
second
harmonic.
g.
Repeat
step
f.
at
as
many
higher
harmonics
as
desired
until
the
harmonic
voltages
become
too
small
to
measure.
In
some
cases,
the
harmonic
fre-
quency
will
be
higher
than
16,
000
cps
which
will
be
outside
the
range
of
the
300A.
2-6
MEASUREMENT
PRECAUTIONS
The
results
obtained
with
the
300A
will
depend
upon
how
clos~ly
the
operator
follows
afew"
simple
but
very
important
operating
precautions.
These
pre-
cautions
are
given
in
step
26
of
PROCEDURE
FOR
CALIBRATION
on
page
12
of
1$
o.
300.1\-2
Service
Manual.
In
addition,
a
20
KC
filter
should
be
used
between
the
voltage
to
be
measured
and
the
input
terminals
of
the
Model
300A
when
voltages
at
frequencies
of
5
KC
or
10
KC
are
being
measured.
This
filter
will
prevent
the
fourth
harmonic
of
the
5
KC
volt3.ge
or
the
second
harmonic
of
the
10
KC
voltage
from
entering
the
20
KC
seJ.ective
amplifier
and
causing
erroneous
measur~ments.
2-7
SELEC
TIVITY
When
operati.ng
the
Model
300A,
it
should
be
borne
in
mind
that
the
instrument
is
a
frequency
selective,
wide
range
voltmeter
whose
selectivity
is
variable.
It
is
necessary
during
operation
to
determine
the
degree
of
selectivity
desired
and
to
adjust
the
instrument
correctly
to
obtain
that
degree
of
selectivity.
Determination
of
the
proper
selectivity
to
use
in
a
particular
measurement
should
primarily
be
based
on
the
fact
that
unwanted
voltages
must
be
attenu-
ated
by
the
selectivity
of
the
instrument
to
less
than
one
third
of
the
voltage
under
measurement.
This
attenuation
is,
in
turn,
dependent
upon
the
order
of
separation
of
unwanted
voltages
from
the
desired
voltage,
and
the
relative
magnitudes
of
the
various
voltages
involved.
Instrument
selectivity
is
controlled
by
the
HALF
BAND
WIDTH
control
which
is
calibrated
from
"30"
to
"145".
These
calibrations
indicate
the
frequency
separation
fr~m
the
center
frequency
at
which
the
selectivity
characteristics
of
the
instrument
attenuates
by
40
db
(99%).
Another
way
of
saying
the
same
thing
is
that
the
HALF
BAND
WIDTH
calibra-
tions
indicate
the
minimum
frequency
separation
from
a
100%
voltage
which
will
permit
accurate
measurement
of
a
3%
voltage.
It
will
often
be
found
convenient
to
use
only
two
degrees
of
selectivity
as
ob-
tained
by
setting
the
HALF
BAND
WIDTH
control
at
"145"
for
minimum
VI
2-7
SELECTIVITY
(Contld.)
selectivity
or
at
"30"
for
maximum
selectivity.
Us
e
mlmmum
selectivity
for
voltages
with
a
fundamental
frequency
higher
than
100
to
300
cps.
Use
maximum
selectivity
for
voltages
with
a
fundamental
frequency
lower
than
100
to
300
cps.
This
system
eliminates
the
necessity
of
determining
whether
an
intermediate
degree
of
selectivity
offers
sufficient
attenuation
for
the
case
at
hand.
Occasionally,
however,
it
is
desirable
to
use
degrees
of
selectivity
which
are
intermediate
between
minimum
and
maximum.
An
example
follows
to
illus-
trate
a
typical
case
of
selectivity
determination.
Refer
to
Fig.
2
on
page
38
of
the
No.
300A-2
Service
Manual
which
shows
the
selectivity
characteristics
of
the
300A
for
the
two
extremes
of
the
HALF
BAND
WIDTH
control.
A
convenient
graph
for
converting
attenuation
in
terms
of
decibels
to
percentage
is
given
in
Fig.
9
on
page
45
of
the
No.
300A-2
Service
ManuaL
The
graphs
of
Figs.
2
and
9
are
used
to
determine
the
setting
of
the
HALF
BAND
WIDTH
control
as
illustrated
in
the
following:
As
sume
that
it
is
desired
to
measure
the
harmonics
of
an
80
cps
funda-
mental
and
that
harmonics
which
are
0.50/0
or
higher
are,of
interest.
Unwanted
voltages
must
be
attenuated
to
less
than
1/3
of
the
voltage
under
measurement
and
for
this
particular
case
it
would
be
1/3
of
1/20/0
or
1/6
of
10/0.
In
other
words,
when
measuring
the
second
harmonic,
the
funda-
mental
must
be
reduced
to
1/6
of
10/0
of
its
value
by
the
300A
selectivity
characteristics.
Referring
to
Fig.
9,
we
see
that
1/6
of
1%
is
equivalent
to
approximately
56
decibels.
Therefore,
the
HALF
BAND
WIDTH
con-
trol
must
be
adjusted
so
that
the
instrument
will
attenuate
by
56
decibels
for
a
frequency
separation
of
80
cps.
Refer
to
Fig.
2
and
sketch
in
a
curve
similar
to
the
two
curves
shown.
The
new
curve
should
pass
through
the
56
db
point
at
80
cps
off
resonance.
Note
the
point
where
the
new
curve
passes
the
40
db
line.
This
point
has
an
abscissa
of
about
50
cycles
off
resonance.
Therefore,
the
HALF
BAND
WIDTH
control
should
be
set
at
"50"
to
obtain
56
db
attenuation
at
80
cps
off
resonance.
The
instrument
must
then
be
calibrated
using
a
HALF
BAND
WIDTH
setting
of
"50"
instead
of
"30"
in
steps
20
through
23
of
PROCEDURE
FOR
CALIBRATION
on
page
12
of
No.
300A-2
Service
Manual.
See
step
26B
on
the
same
page
for
additional
information.
SECTION
III
CIRCUIT
DESCRIPTION
3-
1
GENERAL
The
circuitry
of
the
rFeJ
Model
300A
Harmonic
Wave
Analyzer
is
discussed
on
pages
8,
9,
10,
and
11
of
the
(/!j)
No.
300A-2
Service
Manual.
•
VII
SECTION
IV
MAINTENANCE
4-1
CABINET
REMOVAL
To
remove
the
instrument
from
the
cabinet
it
is
necessary
to
unscrew
the
eight
large
Phillips
head
screws
on
~he
control
panel
and
slide
the
instrument
forward
out
of
the
cabinet.
In
some
older
instruments,
it
may
be
necessary
to
remove
the
wire
connect-
ing
the
bottom
chassis
to
the
metal
plate
in
the
bottom
of
the
cabinet.
This
wire
will
be
found
on
the
rear
of
the
instrument.
4-2
TUBE
REPLACEMENT
Refer
to
page
7
of
Service
Manual
No.
300A-2
for
complete
instructions
on
tube
replacements.
4-3
LOCAL
OSCILLATOR
AMPLITUDE
ADJUSTMENT
This
adjustment
can
be
made
at
any
time
as
directed
in
step
2
of
PRELIMI-
NAR
Y
TESTS
&
ADJUSTMENTS
on
page
13
of
No.
300A-2
Service
Manual.
4-4
VOLTAGE
REGULATOR
ADJUSTMENT
The
output
of
the
regulated
power
supply
section
in
the
300A
should
be
checked
from
time
to
time
as
directed
in
step
1
of
PRELIMINARY
TESTS
&
ADJUST-
MENTS
on
page
13
of
No.
300A-2
Service
Manual.
4-5
HUM
BALANCE
ADJUSTMENT
The
hum
balance
control
R159
is
located
on
the
bottom
deck
of
the
instrument
next
to
the
heater
transformer.
The
procedure
for
adjusting
this
control
is
given
in
FINAL
TEST
step
8
on
page
17
of
No.
300A-2
Service
Manual.
•
4-6
4-7
BALANCED
MODULATOR
ADJUSTMENT
The
procedure
for
adjusting
the
balanced
modulator
to
minimize
harmonic
distortion
is
given
on
page
18
of
No.
300A-2
Service
Manual
in
step
10
under
FINAL
TEST.
SELECTIVE
AMPLIFIER
ADJUSTMENT
The
detailed
procedure
for
adjusting
the
selective
amplifier
system
in
the
300A
is
given
on
pages
14
and
15
of
the
No.
300A-2
Service
Manual.
SECTION
V
TABLE
OF
REPLACEABLE
PARTS
5-1
GENERAL
A
table
of
replaceable
parts
which
is
suitable
for
use
with
all
300A
instruments
is
given
in
the
~
No.
300A-2
Service
Manual.
This
table
begins
on
page
51
of
the
manual.
I
•
OPERATION
AND
SERVICE
MANUAL
FOR
MODEL
300A
HARMONIC
WAVE
ANALYZER
300A-2A
This
is
a
combined
Operation
and
Service
Manual
for
all
c5j;
Model
300A
Harmonic
Wave
Analyzers.
This
manual
contains
complete
operation
and
servicing
in-
structions
for
the
300A
and
may
be
used
in
place
of
the
Instruction
and
Operating
Manual
originally
sup-
plied
with
each
instrument
•
Copyright
1955
by
Hewlett-Packard
Company
The
information
contained
in
this
booklet
is
intended
for
the
operation
and
main-
tenance
of
Hewlett-Packard
equipment
and
is
not
to
be
used
otherwise
or
reproduced
without
the
written
consent
of
the
Hewlett-
Packard
Company.
HEWLETT-PACKARD
COMPANY
275
PAGE
MILL
ROAD,
PALO
ALTO,
CALIFORNIA,
U.S.
A.
300A002
,
..
Typical
Front
View
of
-hp-
Model
300A
Harmonic
Wave
Analyzer
'.
..
TABLE
OF
CONTENTS
&
INDEX
SPECIFICATIONS.
ACCESSOR'IES
AV
AILAB
LE
CONTROLS
&
TERMINALS.
TUBE
COMPLEMENT
&
TUBE
REPLACEMENTS
1.
PAGE
3
3
4
7
CIRCUIT
DESCRIPTION
General
Input
&
Phase
Inverter
Circuits.
Modulator
Cir
cuit
&
Voltage
AInplifier.
Local
Oscillator.
Power
Supply
•
Selective
Amplifier
System.
Voltmeter
Circuit.
CALIBRATION
PROCEDURE
General
Procedure
for
Calibration
.
-'
8
8
9
9
10
10
11
11
11
TEST
PROCEDURE
Instruments
Required
for
Test
Procedure
Preliminary
Tests
&
Adjustments.
1.
Adjustment
of
B+
•
2.
Adjustment
ot:
Local
Oscillator
Injection
Voltage.
3.
Centering
Tuning
Range
of
"F"
Control
•
4.
Check
Os
cillator
Stability
•
S
ele
cti
ve
Amplifier
Alignment
Heat
Run
Check.
Final
Test
1.
Check
&
Adjust
Regulated
B+
Voltage.
2.
Check
&
Adjust
Oscillator
Injection
Voltage
3.
Oscillator
Response
to
Line
Voltage
Change.
4.
Final
Alignment
of
Selective
Amplifier
5.
Adjust
Millivolts
Meter
to
Zero
6.
Centering
Range
of
Control
"C"
7.
Check
for
Carrier
Leakage
•
8.
Check
for
Hum
(Balance
Hum
Control
R
159)
•
9.
Check
Resonance
Curves
•
10.
C
heck
Harmonic
Distortion
(Adjust
Control
R
117)
11.
Checking
Variable
Selectivity
Contol
12.
Checking
Millivolts
Meter
Tracking.
.13.
Checking
Instrument
Sensitivity
14.
Frequency
Calibration
-
Check
&
Adjustment
15.
Frequency
Response
Check
16.
Check
Voltage
Calibration.
17.
Checking
Meter
Sensitivity
Control
18.
Checking
Meter
Multiplier
Control
•
19.
Correcting
Unsteady
Millivolts
Meter
Readings
20.
Adding
"CALIBRATION
PROCEDURE"
Labels
21.
Mechanical
Inspection.
22.
Instrument
Bottom
Plate
Replacement.
23.
Completion
of
Final
Test
CIRCUIT
MODIFICATIONS
General
Top
Deck
Modernizing
Procedure.
Parts
Required
for
Complete
Top
Deck
Modernization.
Bottom
Deck
Modification
Procedure
Modification
to
Reduce
Carrier
Leakage.
Power
Supply
Modification
•
Other
Lower
Deck
Modifications
TROUBLE
SHOOTING
General
Trouble
Chart.
13
13
13
13
14
14
14
16
16
16
16
16
16
16
16
16
17
17
18
18
18
18
19
19
20
20
21
21
21
21
21
21
23
23
24
25
25
26
27
29
29
2.
TABLE
OF
REPLACEABLE
PARTS
General
..•••.••
Replaceable
Parts
Table
•
List
of
Manufacturers
Code
Letters
for
Replaceable
Parts
Table
;
PAGE
37
38
39
40
41
42
43
44
45
46
47
48
49
51
51
50
..
TABLE
OF
CONTENTS
&
INDEX
(Cont'd.)
Fig.
1•
Fig.
2.
Fig.
3.
Fig.
4.
Fig.
5.
Fig.
6.
Fig.
7.
Fig.
8.
Fig.
9.
Fig.
10.
Fig.
11.
Fig.
12.
Fig.
13.
FIGURES
&
ILLUSTRATIONS
Block
Diagram
of
-hp-
Model
300A
Analyzer.
•
Characteristics
of
Selective
Amplifier
System.
Schematic
Diagram
Serial
No.
1330
&
Above
-
Selective
Amplifier
(Top
Deck)
•••••
Schematic
Diagram
Serial
No.
1610
&
Above
-
Modulator,
Oscillator,
Power
Supply
(Lower
Deck).
Typical
Schematic
Diagram,
Serial
No.
1329
&
Below
-
Selective
Amplifier
(Top
Deck)
••••••••••
Typical
Schematic
Diagram,
Serial
No.
1609
&
Below
-
Modulator,
Oscillator,
Power
Supply
(Lower
Deck).
Partial
Schematic
Diagrams
Showing
Early
Circuitry.
Chart
for
Plotting
Selectivity
Curves
• • .
Decibel
to
Voltage
Ratio
Conversion
Graph
Top
View
of
Typical
Bottom
Deck
• • • •
Bottom
View
of
Typical
Bottom
Deck
• • • •
Top
View
of
Typical
Top
Deck
-
Less
Panel.
Bottom
View
of
Typical
Top
Deck
-
Less
Bottom
Plate
.\
\
•
3.
SPECIFICA
TIONS
FREQUENCY
RANGE
-
30
to
16,000
cycles
per
second.
FREQUENCY
CALIBRATION
-
Within
±3%
or
better.
VOL
T
AGE
RANGES
-
Covers
range
between
0.1
millivolt
and
500
volts
with
full
scale
readings
of:
500,
250,
100,
50,
25,
10,
5,
2.5,
l.O,
0.5,
0.25,
and
0.1
volts
plus
full
scale
millivolt
ranges
of
50,
25,
10,
5,
2.5,
and
1.
OVERALL
VOLTAGE
ACCURACY
-
Voltage
readings
are
accurate
to
within
±5%
of
full
scale
value
provided
harmonics
are
spaced
so
as
to
be
suppressed
by
the
selectivity
of
the
instrument.
RESIDUAL
MODULATION
PRODUCTS
-
Suppressed
at
least
65
db.
EUM
VOLTAGE
-
l\t
least
73
db
below
0.5,
:>,
50,
or
500
volts,
depending
upon
input
range
selected.
SELECTIVITY
-
Variable
selectivity
permits
adjusting
frequencies
30
to
145
cps
away
from
the
resonant
fre-
quency
so
they
are
40
db
below
th:~
resonant
frequency
while
maintaining
constant
gain.
-\PPROX.
db
BELOW
MAXIMUM
RESPONSE
3
db
10
db
40
db
60
db
INPUT
IMPEDA
TCE -
'DEVIATIO
FROM
CENTER
FREQUENCY
'.'1ITE
MAXIMUM
SELECTIVITY
3.5
cps
8.0
cps
30.0
cps
53.0
cps
DEVIATION
FROM
CENTER
FREQUENCY
WITH
MINIMUM
SELECTIVITY
14
cps
37
cps
145
cps
280
cps
•
Input
impedance
is
200,000
ohms.
POWER
-
115
or
2.30
volts,
±10%
50
to
60
cps
105
watts
DIMENSIONS
-
Cabinet
Medel:
Rack
Model:
23"
wide,
24"
high,
14"
deep.
19"
wide,
2.2.-3/1"
high,
12"
deep.
l.1)
l.1)
---
o
<'"'l
---
......
.....
"/EIGHT
-
80
pounds
for
either
model.
Shipping
weight
of
cabinet
model
is
150
pounds.
ACC
ESSOR
IES
,1\
V
IIlLAB
LE
-
The
following
accessories
are
available
for
use
with
the
300A.
For
additional
information
see
our
local
sales
representative
or
contact
the
factory
directly.
l"'J
o
o
«:
o
o
DESCRIPTION
Cable
Assembly;
dual
banana
plugs
wlth
374"
spacmg
on
each
end
of
a
4
foot
length
of
RG-58/U
cable.
••••••••
••
•
•••
Cable
Assembly;
dual
banana
plug
with
3/4"
spacing
on
one
end
of
a 4
foot
length
of
RG-58/U
cilble
and
a
UG-88
/U
type
BNC
male
connector
on
the
other
end.
•••• •••••••••••
Transformer,
Bridging;
for
connecting
300A
input
to
a
balanced
line
-hp-
MODEL
NO.
AC-16A
AC-16B
AC-60B
4.
CONTROLS
&
TERMINALS
INPUT
TERMINALS
-
The
two
binding
posts
located
in
the
lower
left
corner
of
the
control
panel
are
the
instrument
input
terminals.
The
lower
binding
post
is
connected
to
the
chassis.
METER
MULTIPLIER
MAX.
INPUT
VOLTAGE
-
This
four
position
rotary
switch
determines
the
maximum
voltages
that
may
be
applied
to
the
in-
strument
without
cir
cuit
overloading.
This
control,
in
conjunction
with
the
METER
SENSITIVITY
control,
indicates
the
multiplication
factor
for
the
MILLIVOLTS
meter
reading.
The
figures
near-
est
the
knob
are
the
maximum
voltages
while
the
outer
figures
are
the
multiplication
factors.
SET
TO
100
FOR
VOLTAGE
MEASUREMENT
-
This
potentiometer
provides
a
control
for
reduCing
the
input
voltage
as
required
for
relative
volt-
age
measurements.
This
control
is
calibrated
from
0
to
100
in
arbitrary
units.
OPERATING
PRECAUTION
VOL
TAGE
MEASUREMENTS
ARE
CORRECT
ONLY
WHEN
THE
SET
TO
100
FOR
VOLTAGE
MEAS-
UREMENT
CONTROL
IS
SET
TO
"100"
AND
THE
HALF
BANDWIDTH
CONTROL
IS
SET
TO
THE
SAME
POSITIONS
SELECTED
FOR
CALIBRATION.
NEGATIVE
FEEDBACK
-
This
control
is
used
to
maintain
constant
amplifier
gain
with
different
settings
of
the
HALF
BAND
WIDTH
control
and
is
calibrated
50-0-50.in
arbitrary
units.
Instructions
for
setting
this
control
are
given
in
the
PROCEDURE
FOR
CALIBRATION.
Some
older
instruments
in
the
field
are
not
provided
with
this
control.
In
these
instruments,
it
will
be
necessary
to
recalibrate
each
time
the
setting
of
the
HALF
BAND
WIDTH
control
is
changed.
HALF
BAND
WIDTH
-
Instrument
selectivity
is
determined
by
the
setting
of
this
control.
The
calibrations
of
30
to
145
on
the
scale
around
this
control
knob
indicate
the
number
of
cycles
off
resonance
the
input
signal
must
be
in
order
to
be
attenuated
40
db.
Instructions
for
setting
this
control
are
given
in
the
PROCEDURE
FOR
CALIBRATION.
FREQUENCY
DIAL
-
..
;
v;
C
C
>
C
C
r-;
The
frequency
dial
and
internal
tuning
capacitor
are
driven
by
the
vernier
knob
in
the
center
of
the
dial.
The
dial
scale
is
calibrated
from
0
to
16
KC
in
terms
of
the
input
signal
frequency.
METER
SENSITIVITY
-
This
tapped
voltage
divider
controls
the
amplitude
of
the
voltage
supplied
to
the
selective
amplifier
and
the
position
of
the
knob
indicates
the
full
scale
value,
in
millivolts,
of
the
meter
scale
in
use.
MILLIVOLTS
METER-
This
meter
indicates
the
voltage
measured
by
the
instrument.
The
meter
has
three
scale
calibra-
tions.
The
scale
in
use
and
the
scale
multiplication
factor
are
indicated
by
the
position
of
the
METER
SENSITIVITY
FULL
SCALE
MILLIVOLTS
and
the
METER
MULTIPLIER
MAX.
INPUT
VOL
T
AGE
controls.
FINE
TUNING
-
This
variable
capacitor
provides
an
incremental
adjustment
for
the
frequency
dial.
The
instru-
ment
is
calibrated
with
this
control
rotated
so
that
the
mark
on
the
knob
skirt
is
straight
up
over
the
center
of
the
control.
ON
-
OFF
SWITCH
-
This
toggle
switch
controls
the
power
supplied
to
the
instrument
from
the
power
line.
When
the
instrument
is
turned
on,
the
indicator
lamp
below
the
toggle
switch
wfll
light.
•
U')
U')
-
o
("1"\
-
-
-
N
o
o
~
o
o
("1"\
5.
CONTROLS
&
TERMINALS
(Contld.)
POWER
CABLE
-
There
are
three
wires
in
the
power
cable.
Two
of
these
wires
(usually
black
and
white)
carry
power
to
the
instrument.
The
remaining
wire
(usually
green)
is
connected
internally
to
the
instru-
ment
chassis
and
protrudes
from
the
power
cable
at
the
plug
end
for
grounding
the
instrument.
FUSE
-
The
fuseholder,
located
on
the
back
of
the
lower
chas
sis
or
deck,
contains
a
1.25
ampere
slo-blo
cartridge
fuse.
The
fuse
may
be
replaced
by
unscrewing
the
fuseholder
cap
and
inserting
a
new
fuse.
Fast
blow
2
ampere
fuses
were
originally
used
in
these
instruments.
The
1.25
ampere
slo-
blo
fuses
are
recommended
for
replacement
since
they
offer
increased
instrument
protection.
Those
instruments
that
have
been
changed
for
230
volt
operation
require
a
0.6
ampere
slo-blo
fuse
for
replacement.
SUB-PANEL
CONTROLS
-
Controls
C,
F,
G.
R,
S,
and
V
are
located
behind
the
door
at
the
bottom
of
the
control
panel.
These
are
non-operating
controls
used
for
instrument
calibration.
CONTROL
C -
This
control
is
used
to
balance
the
capacity
across
the
two
modulation
transformer
primaries
•
CONTROL
F -
This
control
provides
an
adjustment
for
setting
the
local
oscillator
fre-
quency
to
20
KC
when
the
frequency
dial
is
set
to
zero.
CONTROL
G -
Overall
instrument
gain
is
determined
by
the
setting
of
this
control.
CONTROL
R -
This
control
provides
a
resistance
balance
between
the
two
modulation
transformer
primaries.
CONTROL
S -
This
lever
switch
selects
the
input
signal
for
phase
inverter
stage
VIOl.
When
this
switch
is
to
the
right,
the
internal
calibrating
voltage
is
connected
to
VIOl.
With
this
switch
in
the
remaining
position,
the
input
voltage
is
connected
to
the
grid
of
VIOl.
CONTROL
V -
This
control
permits
setting
the
internal
calibrating
voltage
to
5
volts.
A
ten
to
one
voltage
divider
following
this
control
delivers
0.5
volts
for
instrument
calibration.
VOLTS
METER
-
This
meter
measures
the
internal
calibrating
voltage
as
adjusted
by
control
V.
•
..
U1
U1
-
o
C"'\
-
-
-
N
o
o
<
o
o
C"
7.
TUBE
COMPLEMENT
&:
TUBE
REPLACEMENTS
GENERAL
-
Any
tubes
with
RETMA
standard
characteristics
may
be
used
for
replacement
purposes.
However,
as
noted
in
the
instructions
that
follow,
use
of
a
selected
tube
will
improve
instrument
performance
in
some
cases.
The
300A
is
a
high
gain
instrument.
Tubes
that
are
microphonic
or
have
relatively
high
heater
to
cathode
leakage
are
not
desirable.
The
tube type
used
for
some
of
the
stages
in
the
300A
have
varied
with
time.
In
some
cases
use
of
a
later
tube
type
is
recommended
but
not
neces
sary.
If
in
doubt,
replace
tubes
with
the
same
type
found
in
the
instrument.
The
number
of
adjustments
required
will
depend
upon
the
tube
replaced.
The
specific
tests
and/or
adjustments
are
given
in
the
chart
that
follows.
This
chart
also
shows
where
the
procedures
for
these
tests
and
adjustments
can
be
found
in
the
TEST
PROCEDURE
section
of
this
manual.
CIRCUIT
ORIGINAL
RECOMMENDED
TESTS,
ADJUSTMENTS,
AND/OR
REFERENCE
TUBE
TYPE
REP
LACEMENT
SPECIAL
NOTES
VI
thru
V8
6SJ7
6SJ7
FINAL
TEST
procedure
steps
8
and
9.
Low
microphonic
tubes
are
best.
V9
6F8
or
6F8
or
6SN7
Replace
with
same
type
as
in
instrument.
6SN7
FINAL
TEST
step
3.
VIO
6H6
Aged
6H6
Select
tube
giving
minimum
change
in
zero
setting
between
instrument
on
and
off
with
no
input
signal.
Complete
FINAL
TEST
step
3.
F101 2
amp
fast
1.
25
amp
Slo-blo
fuse
gives
better
instrument
pro-
blow
or
1.25
slo-blo
tection.
Use
different
fuse
for
230
volt
amp
slo
-blo
operation
as
noted
under
FUSE
in
the
for
115
V.
CONTROLS
&:
TERMINALS
section.
operation.
R140
lamp
3
watts,
115
10
watts
FINAL
TEST
step
2.
See
step
1
of
OTHER
volts
or
230
volts
LOWER
DECK
MODIFICATIONS
under
10
watts,
BOTTOM
DECK
MODIFICATION
PRO-
230
volts
CEDURE
in
CIRCUIT
MODIFICATIONS
section.
VIOl
6SJ7
6SJ7
FINAL
TEST
procedure
steps
3,
6,
8,
&:
10.
Use
a
tube
with
low
microphonics
and
check
for
a
"hump"
in
the
resonance
V
102
&:
6SJ7
6SJ7
selected
curves
as
directed
in
FINAL
TEST
pro-
V103
as
a
matched
cedure
step
9.
pair.
Vl04
6SJ7
6SJ7
FINAL
TEST
step
3.
Check
for
low
microphonics,
hum,
and
60
cps
"hump".
FINAL
TES
T
step
9a.
V
105
6J7
6J7
Changing
either
tube
will
not
cause
appre-
ciable
change
in
frequency
or
os
cillator
inj
ection
voltage.
Check
by
repeating
steps
2,
3,
8,
10,
and
14
of
FINAL
TEST.
VI06
6F6
6F6
Os
cillator
output
should
be
stable.
Tubes
should
be
non-rnicrophonic.
8.
TUBE
COMPLEMENT
lit
TUBE
REPLACEMENTS
(Cont'd.)
GENERAL
(Cont'd.)
CIRCUIT
ORIGINAL
RECOMMENDED
TESTS,
ADJUSTMENTS,
AND/OR
REFERENCE
TUBE
TYPE
REPLACEMENT
SPECIAL
NOTES
NE16
Neon
Tube
NE16
The
two
tube
types
given
are
not
inter-
V
107
or
or
changeable.
Replace
with
same
type
as
OA2
OA2
found
in
instrument.
Set
B+
according
to
instructions
in
step
1
of
FINAL
TEST.
V
108
6SQ7
or
6SF5
6SQ7
or
6SF5
6L6G,
FINAL
TEST
step
1.
All
of
these
tube
V
109
6L6GA,
6L6GB
types
have
the
same
pin
connections.
Re-
6L6GB,
or
sistor
R164
must
be
in
screen
circuit
if
6Y6
6Y6
is
used.
FINAL
TEST
step
1.
Best
power
supply
5Y3GT,
regulation
will
be
obtained
in
some
cases
VUO
5Z4,
5U4G,
5U4GB
by
replacing
with
the
same
tube
type
as
5U4GA,
or
in
instrument.
All
of
these
rectifiers
5U4GB
are
interchange;;ible
in
the
300A
with
no
change
in
pin
connections.
Voltage
rating
of
output
electrolytic
capacitors
must
not
be
exceeded.
CIRCUIT
DESCRIPTION
GENERAL
-
.
.
The
-hp-
Mode1300A
Harmonic
Wave
Analyzer
is
a
frequency
selective
heterodyne
type
voltmeter
signed
to
measure
individual
components
of
complex
waveforms.
Full
scale
meter
readings
can
be
obtained
from
input
voltages
varying
between
1
millivolt
and
500
volts.
Instrument
selectivity
can
be
varied
to
measure
either
closely
or
widely
spaced
harmonics
over
the
audio
spectrum
from
30
to
16,
000
cps.
Basically,
the
circuit
consists
of
a
phase
inverter,
a
local
oscillator,
a
balanced
mixer,
a
four
section
selective
amplifier,
and
a
vacuum
tube
voltmeter.
In
addition
to
these
basic
circuits,
the
Model
300A
includes
input
and
range
multipliers
as
well
as
an
internal
calibrating
system
for
use
in
standardizing
overall
instrument
gain.
The
block
diagram
given
in
Fig.
1
shows
the
function
of
the
individual
circuits
and
controls.
The
instrument
is
divided
into
two
chassis
with
a
common
front
panel.
The
upper
chassis
con-
tains
the
selective
amplifier
and
vacuum
tube
voltmeter
sections.
The
remalnlng
circuits
are
located
in
the
lower
chassis.
The
schematic
diagram
is
similarly
divided.
INPUT
lit
PHASE
INVERTER
CIRCUITS
-
The
input
terminals
in
the
lower
left
corner
of
the
instrument
panel
are
connected
to
METER
MULTIPLIER
switch
SlOl
which
provides
ranges
of
Xl,
XlO,
XlOO,
and
XlOOO.
In
addition,
each
position
of
this
switch
is
calibrated
in
the
maximum
input
voltage
that
may
be
applied
without
overloading
the
circuits
of
the
instrument.
Erroneous
readings
will
result
from
circuit
clipping
when
the
input
signal
is
higher
than
these
panel
markings.
The
METER
MULTIPLIER
switch
is
followed
by
the
SET
TO
100
control
which
must
be
set
to
the
100
position
in
order
to
obtain
a
corr
ect
voltmeter
reading
when
measuring
the
actual
value
of
the
input
voltage.
Switch
5102
("S")
permits
connecting
the
input
of
the
6SJ7
phase
inverter
tube
VIOl
to
the
input
signal
or
to
the
internal
calibration
circuit.
de-
l.U
0
0
~
0
0
N
-
:-
~
l.U
0
-
U1
C11
..
lI)
lI)
-
o
l""'I
-
.....
.....
N
o
o
<
o
o
l""'I
9.
CIRCUIT
DESCRIPTION
(Cont'd.)
INPUT
&
PHASE
INVERTER
CIRCUITS
-
(Cont'd.)
The
internal
calibration
circuit
obtains
6.3
volts
from
a
heater
winding
on
the
power
transformer.
Control
"V"
permits
setting
the
voltage
to
obtain
a
reading
of
5
volts
on
the
internal
calibrating
voltmeter.
The
values
of
Rl06
and
Rl07
are
chosen
to
obtain
a10
to
1
voltage
division
ratio
and
are
factory
adjusted
to
obtain
a
0.5
volt
calibration
voltage
when
the
calibration
voltmeter
reads
5
volts.
Phase
inverter
VIOl
is
a
triode
connected
type
6SJ7
pentode
tube.
The
load
resistor
(other
than
cathode
resistor
RIll)
for
this
tube
is
effectively
44,000
ohms
and
consists
of
Rl12
and
Rl14
in
serie-s.
With
Rl12
in
the
cathode
circuit
and
Rll4
in
the
plate-circuit,
the
signal
voltage
delivered
to
the
modulator
tubes
through
coupling
capacitors
CI03
and
Cl05
are
equal
in
amplitude
and
180
degrees
out
of
phase
with
each
other.
MODULATOR
CIRCUIT
&
VOLTAGE
AMPLIFIER
-
The
modulator
circuit
consists
of
two
type
6SJ7
tubes
(Vl02
and
Vl03)
in
a
balanced
push-pull
cir-
cuit.
Potentiometer
R117
provide
s
an
adjustment
for
balancing
the
modulator
input
circuits.
This
control
is
set
during
FINAL
TEST
and
is
not
an
operating
control.
Variable
capacitor
CI07
(con-
trol
"C")
and
potentiometer
R123
(control
"R")
provide
balancing
adjustments
for
the
modulator
output
circuits.
The
local
oscillator
voltage
is
injected
into
the
cathode
circuit
of
Vl02
and
Vl03
at
the
top
of
their
common
cathode
resistor
(R120).
The
local
oscillator
operates
at
a
frequency
20
KC
higher
than
the
input
signal.
The
push-pull
modulato1l'
tubes
will
have
the
input
and
local
oscillator
frequencies
present
in
their
output
as
well
as
the
sum
and
difference
frequencies.
Transformer
TlOl
is
designed
for
operation
at
20
KC
and
readily
accepts
the
20
KC
lower
side-
band
and
passes
it
on
to
the
selective
amplifier.
These
amplifiers
are
peaked
to
amplify
a
20
KC
signal.
Any
portion
of
the
original
signal
arriving
at
the
input
to
this
amplifier
system
will
be
rejected
by
the
amplifier.
The
local
oscillator
signal
is
applied
to
Vl02
and
Vl03
from
a
common
source
and
hence
appears
in
both
plate
circuits
in
the
same
phase
and
will
be
cancelled
out
across
the
balanced
primary
of
TlOl.
Balance
is
obtained
by
adjusting
controls
"C"
and
"R".
This
balance
becomes
increasingly
important
at
the
lower
frequency
limit
of
the
300A.
When
the
frequency
dial
is
set
to
zero
the
local
oscillator
frequency
is
20
KC.
If
the
modulator
tubes
are
not
balanced,
the
20
KC
signal
from
the
local
oscillator
will
feed
through
the
selective
amplifier
and
give
an
erroneous
reading
on
the
300A.
Potentiometer
R125
(control
"G")
across
the
secondary
of
TlOl
provides
an
adjustment
for
standard-
izing
overall
amplifier
gain.
METER
SENSITIVITY
switch
Sl03
permits
changing
the
amplifier
input
by
anyone
of
nine
fixed
ratios.
This
effectively
acts
as
a
control
of
meter
sensitivity
and
when
used
in
conjunction
with
the
METER
MULTIPLIER,
switch
SlOl,
provides
18
full
scale
voltmeter
ranges
from
500
volts
to
1
millivolt.
Tube
Vl04
is
a
triode'
connected
type
6SJ7
tube
functioning
as
a
voltage
amplifier.
The
output
from
this
tube
is
connected
to
a
shielded
cable
terminated
by
a
two
prong
plug.
The
shielded
cable
carries
the
20
KC
signal
from
the
lower
chassis
to
the
upper
chassis.
A
two
prong
socket
is
mounted
in
the
upper
chassis
•
LOCAL
OSCILLATOR
-
The
local
oscillator
is
the
resistance-capacity
tuned
circuit
commonly
found
in
-hp-
instruments.
Tubes
Vl05
and
Vl06
function
basically
as
a
two
stage
voltage
amplifier
with
the
output
of
Vl06
coupled
to
the
grid
and
cathode
circuits
of
Vl05.
The
grid
cir
cuit
coupling
produces
regenerative
feedback
to
maintain
oscillation
while
the
cathode
circuit
coupling
produces
degenerative
feedback
to
stabilize
the
oscillator
output.
The
oscillator
tunes
over
a
relatively
narrow
range
from
20
KC
to
36
KC
and
has
constant
output
over
this
range.
Consequently,
the
amplitude
of
the
20
KC
signal
fed
to
the
selective
amplifier
system
is
dependent
upon
the
amplitude
of
the
input
signal.
10.
CIHCUIT
DESCrnPTlON
(Cont'd.)
LOCAL
OSCILLATOR
-
(Cont'd.)
The
frequency
dial
is
calibrakd
to
indicate
the
frequency
of
the
input
signal
and
not
the
local
oscil-
lator
frequL'ncy
which
is
lO
KC
high,"r
than
the
dial
indication.
The
6
to
65
L,,.,f
trimmer
(C
ll-l
control
"F")
provides
an
ac
i
justment
for
setting
the
local
oscillator
frequency
...
ith
the
frequency
dial
set
to
"0".
control
"F"
is
adjusted
for
a
maximum
indication
on
the
300A
voltmeter.
This
adjustmr~'1t
tunes
the
local
oscillator
to
the
20
KC
peak
of
the
selec-
tive
amplifiers.
An
accurately
known
external
source
connected
to
the
300A
input
terminals
can
illso
be
used
for
adjusting
the
local
oscillator.
The
300A
frequency
dial
is
set
to
the
same
fre-
quency
as
the
external
source
and
control
"F"
is
adjusted
for
a
ma.<:imum
indication
on
the
300A
111eter.
Lo
cal
os
cilla
tor
output
is
obtained
fr
om
VIa
6
cathod
e
circuit
and
inj
ected
into
the
cathod
e
cir
cuit
of
VI02
and
VI03.
Injection
voltage
is
set
with
the
frequency
control
dial
at
"a"
by
adjusting
poten-
tiometer
R143
which
controls
negative
feedback
from
VI06
to
the
cathode
of
VI05.
The
20
KC
in-
jection
voltage
measured
at
the
top
of
cathode
resistor
Rl20
for
VI02-
and
VI03
should
be
2
volts.
PO,,'ER
SUPPLY
-
High
voltage
is
obtained
from
a
5U4G/AB
full
wave
rectifier
followed
by
a
two
section
capacity
in-
put
L-C
filter.
This
filtered
dc
output
furnishes
B+
for
all
selective
amplifier
circuits
as
..veIl
as
the
voltmeter
circuit
in
the
upper
chassis.
The
filtered
dc
is
also
passed
through
a
voltage
regu-
lator,
the
output
of
which
supplies
VIOl
through
VI06
in
the
lower
chassis.
An
OA2
voltage
regulator
tube
VI07
supplies
the
necessary
reference
voltage
for
the
6SQ7
regulator
control
tube
VI08
which
in
turn
controls
the
6L6GB
series
regulator
tube
VI09.
Tube
types
for
VI07, VI08.
and
VI09
may
vary
between
instruments.
Potentiometer
R152
is
an
adjustment
for
setting
the
output
of
the
regulated
portion
of
the
power
supply
to
+240
volts.
SELECTIVE
AMPLIFIER
SYSTEM
-
The
selective
amplifier
system
consists
of
a
total
of
eight
type
65J7
tubes.
to
give
effectively
four
amplification
stages.
All
four
stages
function
in
the
sequently,
only
the
first
stage
involving
VI
and
V2
will
be
discussed.
These
tubes
are
paired
same
manner.
Con-
The
signal
from
voltage
amplifier
Vl04
in
the
lower
chassis
is
fed
through
a
shielded
cable
to
the
grid
circuit
of
VI
in
the
upper
chassis.
Coil
LI
in
the
grid
circuit
is
tuned
to
20
KC
by
CI
and
C2.
The
resistor
of
830,
000
ohms
in
the
grid
circuit
prevents
the
preceding
stage
from
loading
the
resonant
circuit.
The
amplified
20
KC
signal
is
developed
across
one
section
of
the
HALF
BAND
WIDTH
control.
With
this
control
rotated
full
counterclockwise,
the
control
arm
is
at
ground
potential
and
there
is
no
feedback
from
V2
to
VI
through
R5, R8,
R
9,
or
RIO
resistors.
Amplifier
gain
is
determined
by
the
fixed
degenerative
coupling
through
R
11
and
C37
between
V2
output
and
VI
cathode
circuit.
Amplifier
selectivity
is
at
minimum
and
is
primarily
determined
by
the
resonant
circuit
in
the
grid
circuit
of
VI.
Resistor
R
74
will
control
the
IIQII
of
the
tuned
circuit
and
hence
also
control
amplifier
selectivity
under
these
conditions.
As
the
HALF
BAND
WIDTH
control
is
rotated
clockwise,
more
and
more
of
the
plate
signal
from
V2
is
fed
back
to
the
grid
circuit
of
VI.
This
signal
is
in
phase
with
the
input
signal
and
the
cir-
cuit
becomes
regenerative.
The
selectivity
of
the
two
stages
becomes
progressively
sharper
as
regeneration
increases.
The
positive
feedback
would
also
cause
an
increase
in
gain
if
it
were
not
for
negative
feedback
through
R5,
R8,
and
RIO
to
the
cathode
of
VI
from
the
same
point
as
the
positive
feedback.
By
design,
circuit
constants
have
been
chosen
to
permit
adjustment
of
the
amount
of
negative
feedback.
By
properly
setting
the
NEGATIVE
FEEDBACK
control,
as
described
in
the
Operating
Instructions,
it
is
possible
to
vary
the
selectivity
of
stages
VI
and
V2
while
maintaining
constant
amplifier
gain.
The
remaining
three
sections
of
the
selective
amplifier
operate
in
an
identical
manner.
Tubes
V3
and
V4
comprise
the
second
section,
tubes
V5
and
V6
the
third
section,
and
tubes
V7
and
V8
the
fourth
s
ectlon.
l1"\
l1"\
-
a
r')
-
.....
.....
N
a
a
~
a
a
r')
11.
CIRCUIT
DESCRIPTION
(Cont'd.)
SELECTIVE
AMPLIFIER
SYSTEM
-
(Cont'd.)
The
HALF
BAND
WIDTH
control
consists
of
four
ganged
potentiometers
which
control
feedback
in
all
four
amplifier
sections
simultaneously.
This
control
is
calibrated
145
to
30.
The
divisions
on
this
scale
indicate
the
number
of
cycles
away
from
the
resonant
frequency
at
which
the
ampli-
fier
response
will
be
down
40
db
(99%).
The
NEGATIVE
FEEDBACK
control
also
consists
of
four
ganged
potentiometers
which
provide
simultaneous
negative
feedback
control
in
all
four
amplifier
sections.
This
control
is
calibrated
50-0-50
in
arbitrary
units.
The
20
KC
toroid
coils
used
in
the
selective
amplifier
sections
are
manufactured
using
the
most
up
to
date
techniques
known
with
the
most
recent
engineering
data
in
order
to
insure
instrument
accuracy
over
an
ambient
temperature
range
of
approximately
55
to
95
degrees
Fahrenheit.
Am-
bient
temperatures
outside
of
this
range
may
necessitate
realignment
of
the
selective
amplifier.
VOLTMETER
CIRCUIT
-
The
vacuum
tube
voltmeter
voltage
amplifier,
V9,
consists
of
two
triode
sections
of
a
type
6SN7GT
tube
connected
in
a
conventional
resistance
coupled
amplifier
circuit.
The
output
of
this
amplifier
is
fed
to
a
6H6
tube
in
a
full
wave
rectifier
circuit.
The
ground
return
for
the
rectifier
circuit
is
made
through
the
cathode
resistor
for
the
first
triode
section.
This
introduces
inverse
or
nega-
tive
feedback
which
stabilizes
the
vacuum
tube
voltmeter
circuit.
The
indicating
meter
has
a
basic
0-1
milliampere
movement
with
the
scale
calibrated
in
three
ranges
of
0-1,
0-2.5,
and
0-5
millivolts.
CALIBRA
nON
PROCEDURE
GENERAL
-
The
instrument
should
be
given
at
least
30
minutes
for
warm
up
before
starting
the
calibration
procedure.
This
warm
up
will
allow
the
circuits
to
reach
a
stable
operating
condition.
It
is
also
advisable
to
check
the
calibration
after
the
instrument
has
been
operating
for
more
than
one
hour.
PROCEDURE
FOR
CALIBRATION
-
1.
Set
the
main
tuning
dial
to
"0".
2.
Set
the
FINE
TUNING
so
that
the
line
is
vertical.
3.
Set
METER
SENSITIVITY
to
"SaO".
4.
Set
HALF
BAND
WIDTH
to
"30".
5.
Set
NEGATIVE
FEEDBACK
to
"0".
6.
Set
METER
MULTIPLIER
to
"XIOOO".
7.
Set
input
gain
control
potentiometer
(SET
TO
100
FOR
VOLTAGE
MEASUREMENT)
full
counterclockwise
to
"a".
This
control
and
the
METER
MULTIPLIER
have
no
effect
on
the
calibration
procedure
except
to
isolate
the
input
terminals
from
the
balance
of
the
circuits.
8.
Set
switch
"S"
to
the
left
(position
vertical
to
panel).
9.
Set
control
"G"
to
the
center
of
its
range.
10.
-Adjust
control
"F"
for
a
maximum
MILLIVOLTS
meter
indication.
If
MILLIVOLTS
meter
reads
off
scale,
rotate
control
"G"
to
bring
pointer
on
scale.
11.
Adjust
controls
"C"
and
"R"
for
a
minimum
MILLIVOLTS
meter
reading.
Rotate
con-
trol
"G"
to
increase
meter
readings
and
also
switch
METER
SENSITIVITY
to
lower
scales
in
order
to
increase
meter
readings.
12.
Set
HALF
BAND
WIDTH
to
"145".
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