National Radio NCL 2000 User manual
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37
WASHINGTON
STREET •
MELROSE,
MASSACHUSETTS
NCL
2000
LINEAR
POWER
AMPLIFIER
NICL•2000
el
I
00
00
•
.L\
You
now
own
a
product
manufactured
by
one
of
the
world's
oldest
and
most
highly
respected
manufacturers
of
quality
communications
equipment.
National
has
manufactured
superb
communications
devices
for
nearly
half
a
century.
Our
experience
is
unequaled.
More
than
75
per
cent
of
our
highly
skilled
test
and
assembly
people
have
been
with us
for
more
than
25
years —
an
astonishing
record
in
the
relatively
young
electronics
industry.
Our
people
know
their
business . . .
take
pride
in
their
fine
workmanship —
workmanship
so
outstanding
that
many
National
receivers
purchased
over
30
years
ago
are
still
in
daily
use.
We
manufacture
most
of
the
components
used
in
our
equip-
ment . . .
and,
in
fact,
National
has
been
a
prime
supplier
of
electronic
components
to
other
impórtant
electronic
manufacturers
and
government
agencies
for
many
years.
As
a
result,
we
enjoy
unusual
control
of
component
part
quality.
We
strongly
recommend
that
you
carefully
study
the
in-
struction
manual
before
attempting
to
use your
new
equip-
ment.
We
are
sure
you
will
find
that
maximum
perfor-
mance
will
be
achieved
with
complete
understanding
of
its
controls
and
operating
features.
Your
new
National
equipment
has
undergone
an
intense
series
of
rigid
quality
control
tests.
However,
as with
any
complex
electronic
equipment,
it
is
possible
that
a
defect
may
appear
as
a
result
of
rough
handling
during
shipment
or
through
circumstances
beyond
our
immediate
control.
For
this
reason,
we
suggest
that
you
inspect
your
new
equipment
for
such
damage
as
soon
as
it
is
unpacked.
In
all
cases
of
in-
transit
damage
a
claim
must
be
filed
against
the
carrier.
The
component
parts
of
this
equipment (
exclusive
of va-
cuum
tubes
and
transistors)
are
guaranteed
to
be
free
from
defective
material
and
workmanship,
and
repair
or
replace-
ment
will
be
made
on
any
part
found
to
be
defective
upon
examination,
provided
that
the
unit
is
delivered
to
your
dealer,
authorized
service
agency
or
to
the
company,
pursuant
to
the
instructions
below,
within
one
year
from
the
date
of
sale
to
original
purchaser.
On
units
returned
during
the
initial
90
day
period,
National
Radio
Company,
Inc.
will
absorb
the
labor
cost
of
installation;
for
the
remainder
of
the
guarantee
period the
customer
will
be
charged
for
such
cost.
The
enclosed
guarantee
card
must
be
returned
to
National
Radio
Company,
Inc.,
within
ten
days
from
date
of
purchase
in
order
to
validate
the
guarantee.
Naturally,
this
guarantee
does
not
extend
to
any
product
L',\M
11
which
has
been
subjected
to
misuse,
neglect,
accident,
improper
installations,
or
use
in
violation
of
instructions
furnished
by
us.
Nor
does
it
extend
to
units
which
have
been
repaired
or
altered
outside
of
our
factory
or
its
authorized
agencies,
nor
to
units
where
the
serial
number
has
been
removed
or
defaced.
Should
your
new
National
equipment
require
servicing
please
do
one
of
the
following,
whichever
is
most
con-
venient:
1.
Return
it
to
the dealer
from
whom
you
purchased
it.
2.
Bring
it
to
one
of
our
authorized
service
agencies.
3.
Write
to
the
Service
Manager,
National
Radio
Company,
Inc.,
37
Washington
Street,
Melrose,
Mass.
and
describe
the
difficulty.
State
type
of
unit
and
serial
number.
De-
scribe
as
completely
as
possible
the
apparent
defect.
If
we
feel
that
the
unit
should be
returned
to
the
fac-
tory
we
will
give
you
written
authorization
to
ship
the
unit
to
us.
Notify
us
that
you
are returning
the
unit
and
ship
prepaid
and
fully
insured
in
the
original
specially
designed
shipping
carton.
Your
unit
will
receive
prompt
and
careful
attention.
If,
in
our
judgment
the
unit
is
indeed
defective,
repair
or
re-
placement
will
be
made
at
no
cost
to
you
if
the
unit
is
returned
within
90
days
after
date
of
original
purchase.
Should
the
unit
be
returned
to
us
after
90 days
from
date
of
purchase
but
before
365
days
have
elapsed,
again,
if
in
our
judgment
the
unit
is
indeed
defective,
National
Radio
Company
will
provide
a
replacement
of
any
such
defective
part (
except
vacuum
tubes
cr
transistors).
If
you
wish
us
to
install
the
part,
you
will
be
billed
only
for
labor
costs
involved.
At
the
end
of
one
year,
after
expiration
of
guarantee,
service
will
be
billed
to
you
at
cost
of
parts
and
labor
only.
This
extended
guarantee
super-
sedes
all
previous
warranties
of
National
Radio
Company,
Inc.
and
is
in
lieu
of
all
other
warranties
expressed
or
im-
plied.
Damages
arising
out
of
a
breach
of
this
guarantee
are
limited
to
repair
or
replace-
ment
of
the
defective
part
as
stated
above.
We
naturally
re-
serve
the
right
to
change
or
improve
our
products
without
imposing
any
obligation
upon
ourselves
to
so
modify
pro-
ducts
previously
manufactured.
Your
new
National
Radio
Com-
pany
equipment
is
the
finest
of
its
type.
It
was
skillfully
designed,
carefully
manufac-
tured
and
thoroughly
tested.
We
are
confident
that
your
choice
of
our
equipment
will
result
in
many
years
of
plea-
sure
NCL-2000
The
National
NCL-2000
is
a
tue
1000
watt '
D
C,'',
2000
watt
PEP
linear
amplifier
in
a
desk
top
cabinet
wit!-
1
self-contained
power
supply.
It
provides
every
feature
for
op-
erating
convenience
and
safety
that
an
amplifier
designed
to
commercial
specifications
should
have --
and
many
features
that
nc
other
amplifier
of
comparable
power,
at
any
pr;ce,
possesses.
The
NCL-2000
Ltil
zes
output
tubes
designed
for
high
power
SSB
service
with
800
watts
of
available
plate
dissipation
to
provide
rue
2000
watt
PEP
operation
at
high
effi-
ciency.
Output
at
2
KW
input,
key
down,
is
as
much
as
1400
watts
on 10
meters.
Out-
put
tubes
and
power
supply
components
allow
AM, CW,
or
RT
Ty
service
at
a
full
kilo—
watt
all
day
long.
The
NCL-2000
may
be
driven
by
any
exciter
providing
20
to
200
watts
cf
peak
output,
and
all
necessary
controls
and
relays
are
incorporated
for
use
with
transce:vers
such
as
the
NCX-3
or
separa'e
transmitter-
receiver
combinations.
The
antenna
is
automcHcally
switched
to
the
exciter
when
plate
voltage
is
removed,
providing
instant
choice
of
nigh
or
low
power
to
meet
band
conditions,
and
an
internal
50
ohm
dummy
load
allows
easy
exciter
tune-up (
with
amplifier
plate
voltage
off)
with
relative
exciter
powe-
indicated
on
the
NCL-2000
multi -
meter.
ALC
output
is
provided
fo-
use
with exciters
incorporating
such
provisions,
and
pro-
tective
features
for
the
safety
of
the
operator
and
the
equipment
are
conplete --
positive
cabinet
interlock
and
automatic
B+
shorting
bcr,
one-
minute
time
delay
and
separate
over-
load
relay.
The
National
NCL-2000
is
the
finest
amateur
amplifier
ii
is
possible
to
buy,
and
yet
costs
very
little
mare
than
run
of
the
If
1000.
watt
PEP
rigs.
Compare
its
features
with
any
equipment
on
the
market,
at
cny
price,
and
you'll
agree.
National
Radio
Company,
Inc. •
37
Wasnington
St,
Melrose,
Mass.
02176 •
Area
Code
617
665.4800 •
TWX-617-665-5032
A
Whohy
Owned
Subsidiary
of
National
Co.,
Inc.
SPECIFICATIONS
1.
Frequency
Range:
80,
40,
20,
15,
and
10
meter
bands
plus
overlap
at
band
edges.
2.
Power
Input (
SSB):
1000
watts
average,
2000
watts
PEP.
Power
Input (
AM,
CW,
RTTY):
1000
watts.
Power
Output (
SSB):
1300
watts
minimum
on
all
bands.
Power
Output (
CW,
RTTY):
600
watts
minimum
on
all
bands.
Power
Output (
AM):
300
watts
minimum
on
all
bands.
3.
Output
Impedance
Matching
Range:
40-60
ohms
minimum.
4.
Input
Impedance:
50
ohms
nominal,
unbalanced.
5.
Drive
Requirements:
20
to
200
watts
PEP,
adjustable.
6.
Component
Ratings:
All
components
specified
to
best
commercial
practice;
all
power
components
rated
at
1000
watt
average
input
i.c.a.s.
7.
Power
Supply:
Bias
voltage
electronically
regulated,
plate
supply
utilizes
solid state
rectifiers
in
full
wave
voltage
doubler
configuration
for
better
ripple &
regulation,
rated
to
deliver
2500
volts
at
800
ma.
key
down.
8.
Distortion
Products
at
Full
Rated
Output:
30-45
db
signal
to
distortion
ratio.
9.
Noise:
NLT
40
db
down.
10.
ALC:
Rear
panel
output
for
use
with
equipment
incorporating
such
provision.
11.
Ambient
Temperature
Range:
To
45
°
C.
12.
Ambient
Humidity
Range:
To
90%.
13.
Altitude:
To
8,000
ft.
14.
Tune-up
Provisions:
SSB-CW
switch
permits
tune-up
at
1000
watts
to
comply
with
F.C.C.,
built-in
dummy
load
for
exciter
permits
tune-up
of
exciter
into
amplifier
grid
circuit
with
amplifier
plate
voltage
removed
and
with
relative
exciter
power
indicated
on amplifier
multi-
meter.
15.
Safety
Provisions:
Primary
power
fuses,
one
minute
time
delay,
plate
current
overload (
one
ampere),
hinged
cover
utilizes
Dzus
fasteners
with
plate
power
interlock,
automatic
shorting
bar
connects
plate
power
to
ground (
when
cover
is
raised)
in
case
of
interlock
or
ble
eder
failure.
16.
Internal
Relays:
Plate
power
time
delay,
plate
current
overload,
plate
power,
antenna
relay.
17.
Metering:
Precision
plate
milliammeter,
rear
illuminated,
0-1000
ma.,
precision
multi-
meter,
rear
illuminated;
0-5000
plate
volts,
0-50
screen
milliamperes,
0-50
grid
milliamperes,
Exciter
Relative
Power
output.
18.
Front
Panel
Controls:
Power
On-
Off,
SSB,
CW,
plate
power
On-
Off,
power
pilot
light,
amplifier
Ready
light,
plate
power
light.
Bandswitch,
Multi-
meter
switch,
P.A.
Tune,
P.A.
Load.
19.
Rear
Panel:
Amplifier
Output,
Transceiver
Input,
Transmitter
Input,
Receiver
Input,
ALC
Output,
control
relay
terminals,
Grid
Bias
Adjust,
Grid
Bias
Test
Jack,
fuses,
primary
power
input.
20.
Tube
and
Semi-
Conductor
Complement:
Two
RCA
8122
output
tubes,
13
semi-
conductors
for
rectification
and
regulation.
21.
Size:
7
5/8"
H,
16
1/2"
W,
12
3/4"
D.
22.
Weight:
62
lbs.
23.
Primary
Power
Requirements:
115
V.
A.C.
60
cycle
single
phase,
or
230
V.
A. C.
60
cycle
single
phase,
3
wire
neutral
ground.
Current
15
amperes
maximum
at
230
V.
May
be
operated
with
50
cycle
source
at
reduced
input
or
with
60
cycle
source
for
fan.
24.
Warranty:
Tubes,
transistors
and
labor
warranted
for
three
months,
all
other
components
for
12
months
after
date
of
purchase.
ANT.
•_-
RCVR
XCVR
XMTR
ANT.
RELAY
CONTROL
SHORT
TO
TRANSMIT
230 VOLT
CONNECTION
117
VOLT
CONNECTION
A
LC
OUT
J2
P
J4
P
J5
P
C50
K 1
ANTENNA
a,
e,
RELAY
°=•-
▪ •
RI
180
7W
,
R8
180
7W
R2
180
7W
,
R9
;
180
7W
R3
180
7W
,
RIO
;
180
7W
R4
'180
7W
,
RhI
180
7W
:
R5
180
7W
,
R12
180
7W
:R6
'Ieco
7W
,
RI3
180
7W
R7
180
7W
OPTIONAL
GRID
CONNECTION
C2I
.01
RI4
180
7W
II
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C30
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50001
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R46
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I.
ALL
RESISTORS
IN
OHMS;
1/2
WATT,
10%
UNLESS
OTHERWISE
NOTED
2.
ALL
CAPACITORS
IN F;
500V,
10%
UNLESS
OTHERWISE
NOTED
3.
BAND
SWITCH
SHOWN
IN
CCW.( 80
METER)
POSITION
4.
MULTI
METER
SWITCH
SHOWN
IN
CCW
(PLATE
VOLTAGE )
POSITION
S44
FRONT
L 3
2.5mh
S4B
BACK
IC41
- .
01
0-1
VDC _
MULTI
METER
/
INDEX
SECTION
1
GENERAL
DESCRIPTION
3
SECTION
2
INSTALLATION
4
2.1
CAUTION
2.2
Unpacking
and
Tube
Installation
2.3
Power
Connection
2.4
Antenna
Connection
2.5
ALC
Connection
2.6
Exciter
Requirements
2.7
Exciter
Connections
2.8
RF
Exciter
Connection (
Transceiver)
2.9
RF
Exciter
Connection (
Separate
Transmitter
and
Receiver
With
External
Antenna
Transfer
Relay)
2.10
RF
Exciter
Connection (
Separate
Transmitter
and
Receiver
Without
External
Antenna
Transfer
Relay)
2.11
Relay
Connection
2.12
Ground
Connection
SECTION
3
OPERATION
8
3.1
Explanation
of
Controls
3.2
Preliminary
Adjustment
3.3
CW
Tune-
Up
Procedure
3.4
SSB
Tune-
Up
Procedure
3.5
AM
Tune-
Up
Procedure
SECTION
4
THEORY
OF
OPERATION
12
4.1
Class
ot
Operation
4.2
Grid
Bias
Supply
4.3
Input
Circuit
4.4
ALC
4.5
Output
Circuit
4.6
Metering
4.7
Primary
Power
Circuits
4.8
CW-SSB
Mode
Selection
4.9
Antenna
and
Transmit
-
Standby
Switching
4.10
Cut-
Off
Bias
SECTION
5
SERVICE
INSTRUCTIONS
15
5.1
Tube
Replacement
5.2
Filter
Capacitor
Board
Removal
5.3
Cabinet
Removal
5.4
Front
Panel
and
Side
Gusset
Removal
5.5
Regulator
Transistor
Change
5.6
Air
System
Cleaning
5.7
Grid
Resistor
Tap
Change
SECTION
6
TROUBLE
SHOOTING
17
SECTION
7
PARTS
LIST
19
SECTION
1
GENERAL
DESCRIPTION
The
NCL-2000
is
a
1000
watt
average,
2000
watt
PEP
linear
amplifier
for
the
80
through
10
meter
amateur
bands,
housed
in
a
desk-
top
cabinet
with
self-contained
power
supply.
It
utilizes
two
type
8122
miniature
ceramic
tetrodes (
in
parallel)
in
its
output
circuit,
which
provide
800
watts
of
available
plate
dissipation
to
allow
operation
at
the
maximum
legal
input
with
high
efficiency
and
ex-
cellent
linearity.
The
output
circuit
components,
power
supply,
and
other
components
in
the
NCL-
2000
are
rated
to
allow
operation
at
1000
watts
steady
carrier
input
for
AM,
CW,
FM
and
RTTY
service.
The
NCL-2000
utilizes
a -
passive
untuned
grid
circuit
which
allows
the
amplifier
to
be
driven
to
full
output
from
any
exciter
providing
from
20
watts
to
200
watts
of
power
output.
In
addition,
the use
of
a
100
watt
non-
inductive
swamping
re-
sistor
in
the
grid
circuit
provides
the
operator
with
the
ability
to
load
and match
his
exciter
into
the
amplifier
grid
circuit
without
placing
a
signal
from
either
the
exciter
or
the
amplifier
on
the
air.
The
grid
swamping
resistor
functions
as
a
dummy
load
in
this
instance,
and
relative
power
output
from
the
exciter
is
indicated
as
final
grid
current
on
the
NCL-2000
multimeter.
The
NCL-2000
incorporates
a
built-in
antenna
transfer
relay
with
all
contacts
and
coaxial
jacks
necessary
to
allow
inter-
connection
with
either
transceivers
such
as
the
NCX-3
or
the
NCX-5,
or
separate
transmitter-receiver
combinations,
without
the
necessity
for
additional
controlled
relays.
In-
stantaneous
selection
of
either
high
power (
using
the
amplifier)
or
low
power
straight-
through
op-
eration
of
the
exciter
is
possible
by
simply
turning
the
PLATE
switch
of
the
NCL-2000
ON
or
OFF.
Two
screwtype
connections
are
available
at
the
rear
of
the
amplifier
to
allow
control
of
its
internal
an-
tenna
transfer
relay
by
an
external
switch.
The
internal
antenna
transfer
relay
of
the
NCL-2000
utilizes
a
separate
pair
of
contacts
to
automatically
bias
off
the
output
tubes
when
the
amplifier
is
in
the
standby
mode
to
prevent
tube
noise
from
ap-
pearing
in
the
receiver
and
to
reduce
standby
dis-
sipation
in
the
amplifier.
ALC
circuitry
is
incorporated
in
the
NCL-2000,
with
an
output
jack
to
allow
ALC
control
of
an
exciter
incorporating
ALC
input.
The
ALC
voltage
from
the
amplifier
is
developed
when-
ever
grid
current
exceeds
the
point
at
which
limit-
ing
or "
flat-
topping"
of
the
amplifier
occurs.
The
NCL-2000
incorporates
two
D'Arsonval
precision
meters
—
a
plate
current
meter
with
a
0
to
1000
ma.
scale
and
a
multimeter
with
readings
selected
by
a
front
panel
MULTIMETER
switch.
Plate
voltage,
screen
current,
grid
current,
and
exciter
relative
output (
grid
current)
may
be
sel-
ected
by
the
MULTIMETER
switch.
Front
panel
switches
are
provided
for
primary
power,
plate
voltage,
and
choice
of
either
SSB
or
CW
mode.
Pilot
lamps
are
provided
to
indicate
primary
power
ON,
plate
power
ON,
and
operation
of
the
one-
minute
time
delay
relay.
In
addition
to
this
protective
relay,
a
1200
ma.
plate
overload
relay
is
incorporated
in
the
NCL-2000,
as
well
as
primary
fusing.
Two
separate
safety
interlocks
are
built
in
—
a
lid
interlock
which
breaks
power
to
the
plate
relay,
and
a
spring-
actuated
mechanical
shorting
bar
which
discharges
residual
plate
voltage
to
ground
when
the
lid
is
raised.
The
mechanical
shorting
bar
also
serves
as
added
protection
against
the
remote
possibility
of
plate
interlock
failure
or
an
open
bleeder
resistor.
Should
either
failure
oc-
cur,
no
damage
will
be
done
to
the
amplifier
by
the
action
of
the
mechanical
shorting
bar
since
the
overload
relay
will
immediately
open.
The
NCL-2000
may
be
operated
from
either
a
230-
volt,
3
wire
single-phase
supply
or
from
a
115-
volt,
2
wire
line.
All
power
supply
components
are
rated
for
50
cycle
operation,
but
in
such
in-
stances
the
cooling
fan
must
be
operated
from
a
separate
60
cycle
source
for
full
power
rating.
3
INSTALLATION
SECTION
2
2.1
CAUTION
2.1.1
THE
VOLTAGES
USED
IN
THE
NCL-
2000
ARE
LETHAL.
NEVER
DEFEAT
THE
ELECTRICAL
OR
MECHANICAL
SAFETY
INTERLOCKS.
NEVER
WORK
INSIDE
THE
EQUIPMENT
WITH
PRI-
MARY
POWER
CONNECTED.
2.1.2
THE
OUTPUT
TUBES
USED
IN
THE
NCL-2000
REQUIRE
A
CONSTANT
SUP-
PLY
OF
AIR
FROM
THE
COOLING
FAN
AT
ALL
TIMES.
TO
PREVENT
OVERHEATING
AND
SUBSEQUENT
DAMAGE,
DO
NOT
PLACE
OBJECTS
ON
TOP
OF
THE
NCL-2000
CABINET;
DO
NOT
ACCIDENTALLY
BLOCK
THE
AIR
INTAKE
UNDERNEATH
THE
CABINET.
2.1.3
BE
EXTREMELY
CAREFUL
WHEN
IN-
SERTING
OR
REMOVING
THE
8122
OUTPUT
TUBES;
CAREFULLY
NOTE
THE
WAY
THE
BASE
AND
THE
SOC-
KET
ARE
KEYED,
AND
INSERT
THE
TUBES
GENTLY
INTO
THE
SOCKETS
WITHOUT
USING
FORCE.
2.14
NEVER
OPERATE
THE
NCL -
2 0 0 0
WITHOUT
AN
ANTENNA
OR
ADE-
QUATE
DUMMY
LOAD
CONNECTED.
LIGHT
BULBS
WILL
NOT
PRESENT
THE
PROPER
LOAD
IMPEDANCE.
DAMAGE
TO
THE
OUTPUT
CIRCUIT
IS
CERTAIN
TO
OCCUR
IF
THE
NCL-
2000
IS
RUN
UNLOADED.
DO
NOT
OPERATE
THE
NCL-2000
INTO
AN
ANTENNA
SYSTEM
WITH
A
HIGH
VSWR.
2.1.5
PERSISTENTLY.
BLOWN
INPUT
FUSES
OR
CONSTANT
OVERLOAD
RELAY
TRIPPING
INDICATES
A
MALFUNC-
TION
OR
FAULTY
INSTALLATION.
CEASE
OPERATION
AND
DETERMINE
THE
DIFFICULTY
BEFORE
PERMA-
NENT
DAMAGE
OCCURS.
2.1.6
MAKE
CERTAIN
THAT
THE
PRI-
MARY
WIRING
TO
THE
STATION
IS
ADEQUATE
TO
HANDLE
THE
RE-
QUIREMENTS
OF
THE
NCL-2000.
30
AMPERE
115
V.A.C.
SERVICE
OR
THREE
WIRE
20
AMPERE
230
V.A.C.
SERVICE
IS
NECESSARY
TO
COMPLY
WITH
FIRE
LAWS
AND
INSURANCE
REQUIREMENTS
IN
MOST
PARTS
OF
THE
UNITED
STATES.
2.1.7
REFER
AGAIN
TO
2.1.1.
ABOVE.
2.2
UNPACKING
AND
TUBE
INSTALLATION:
Carefully
unpack
the
NCL-2000,
its
plugs,
tubes
and
chimneys,
setting
aside
all
packing
mat-
erial
for
possible
future
use.
Lift
the
lid
by
turn-
ing
the
fasteners
counter-
clockwise
one-
quarter
turn,
and
inspect
for
visible
shorts
or other
damage
which
may
have
occured
during
shipping.
If
dam-
age
is
evident,
immediately
notify
and
file .
claim
with
the
carrier.
Place
the
tube
chimneys,
narrow
end
up,
under
the
tube
clamps,
carefully
insert
the
tubes
to
prevent
damage
to their
pins,
and
tighten
the
tube
clamps.
Also,
check
to
see
that
the
time
delay
relay (
which
looks
like
a
miniature
tube)
located
just
behind
the
front
panel
is
seated
in
its
socket.
2.3
POWER
CONNECTION:
The
NCL-2000
is
designed
for
operation
from
either
115-
volt,
2-
wire,
or
230-
volt,
3-
wire
single
phase
service.
Under
peak
power
input
conditions,
the
NCL-2000
may
draw
in
excess
of 10
amperes
from
a
230-
volt
service
or
in excess
of
20
amperes
from
a
115-
volt
service.
This
latter
power
require-
ment
will
exceed
the
capabilities
of
most
home
115-
volt
circuits.
We
therefore
strongly
recommend
op-
eration
of the
NCL-2000
from
a
230-
volt,
20
ampere
supply
circuit.
Such
a
circuit
will,
in
addition,
generally
have
superior regulation
to
a
115-
volt
circuit.
In
the
event
that
a
230-
volt
circuit
cannot
be
supplied,
a
special
115-
volt.
circuit
rated
at
30
amperes
should
be
provided.
Operation
on
the
230-
volt,
2-
wire
service
available
in
many
countries
will
necessitate
the
use
of
a
2-
wire
to
3-
wire
1:1
conversion
transformer.
50
cycle
operatibn
is
per-
missible
provided
that
the
cooling
fan
is operated
from
.a
separate
60
cycle
supply.
If
such
a
supply
is
unavailable,
the
NCL-2000
may
be
operated
at
reduced
input.
4
The
NCL-2000
is
shipped with
the
primary
power
connections
wired
for
230-
volt
operation
and
a
power
cord
for
230-
volt
operation
is
supplied.
No
power
plug
is
supplied
because
the
enormous
variety
of
230-
volt
sockets
makes
it
impossible
to
supply
a
single
plug
to
meet
all
possibilities.
Pro-
cure
a
suitable
230-
volt
plug
and
wire
the
red
and
black
wires
of
the
cable
to
the
hot
sides
of
the
plug
and
the
white
wire
to
the
neutral.
If
115-
volt
operation
is
contemplated,
a
sepa-
rate
power
cord
and
plug
should
be
obtained.
Number
8/2
cable
is
recommended
to
minimize
line
drop
under
the
25
ampere
peak
load
of
the
NCL-2000.
To
install
the
115-
volt
cable,
remove
the
four
self-
tapping
screws
of
the
primary
power
junction
compartment
cover,
the
cover
itself,
and
the
230-
volt
cable.
Prepare
the
new
cable
by
con-
necting
the
plug,
stripping the
sheath
of
the
other
end
back
five
inches
and
stripping
and
tinning
the
conductors
approximately
one
inch.
Then,
insert
the
new
cable
far
enough
so
that
it
bottoms
in
the
compartment,
dressing
the
conductors
to
the
right
ana
below
the
barrier
strip.
Remove
the
existing
jumper
and
wire
new
jumpers
and
the
new
cable
as
shown
in
Figure
1
or
as
shown
in
the
diagram
on
the
compartment
cover.
115
VAC
T
230
VAC •
NEUTRAL
PRIMARY
2.4
ANTENNA
CONNECTION:
The
antenna
to
be
used
with
the
NCL-2000
should
present
a
50
ohm
impedance
and
a
VSWR
of
2:1
or
less.
It
should
be
fed
with
50
ohm
cable
(RG-8A/U
size
minimum),
and
provided
with
a
PL-
259
UHF
series
coaxial
plug.
Connect
it
to
the
coax
jack
marked "
ANT."
2.5
ALC
CONNECTION:
The
NCL-2000
contains
an
ALC
circuit
that
provides
a
negative
voltage
at
the
rear
panel
phono
jack
whenever
the
NCL-2000
is
overdriven
or "
flat-
topped."
This
may
be
used
with
exciters
incor-
porating
an
ALC
input.
Connect
the
ALC
out-
put
to
the
exciter
ALC
input,
using
a
shielded
cable
with
suitable
connectors.
See
paragraph
4.4
for
description
of
this
circuit.
Use
of the
ALC
connection
is
optional.
2.6
EXCITER
REQUIREMENTS:
The
NCL-2000
is
shipped with
the
output
tube
grids
tapped
down
on
the
grid
swamping
resistor
for
use
with
exciters
providing
80
to
200
watts
of
peak
output.
If
the
exciter
peak
output
is
less
than
80
watts,
see
paragraph
5.7
which
describes
the
alteration
of
the
tap
on
the
grid
swamping
resistor
for
use
with
low
power
driver
sources.
POWER
CONNECTIONS
RED
WHITE
I 2 3 4
o
UH
o
o
BLACK
FIGURE
1
5
JUNCTION
BOX
(COVER
REMOVED)
2.7
EXCITER
CONNECTIONS:
The
NCL-2000
incorporates
all
necessary
an-
tenna
change-
over
relay
terminals
to
allow
its
use
with
either
transceiver
or
transmitter-
receiver
com-
binations.
When
used
with
a
transceiver
or
with
a
transmitter-
receiver
combination
with
their
own
separate
antenna
change-
over
relay,
high-
power
or
low-
power "
straight
through"
operation
may
be
selected
by
simply
turning
the
amplifier
plate
volt-
age
ON
or
OFF.
The
NCL-2000
requires
no
sep-
arate
antenna
change-
over
relay
when
used
with
transmitter-
receiver
combinations,
but
in
this
case
the
NCL-2000
must
be
used
at
all
times,
since
no
straight-
through
connection
is
available.
2.8
RF
EXCITER
CONNECTION
(
Transceiver)
(See
figure
2)
The
NCL-2000
has
been
designed
to
provide
for
automatic
connection
of
the
antenna
directly
to
the
exciter
during
receiving
periods
or
when
the
NCL-2000
plate
supply
is
off.
This
eliminates
the
usual
necessity
for
a
separate "
extra"
antenna
change-
over
relay,
and
further
provides
straight-
through
operation
of
the
transceiver
without
the
linear
when
desired.
A
transceiver
such
as
the
NCX-3
or
the
NCX-5
should
have
its
antenna
in-
put/output
connected
directly
to
the
NCL-2000
coaxial
jack
marked "
XCVR"
with
a
50
ohm
cable
and
PL
259
connectors.
The
input
swamping
resistor
of
the
linear
presents
a
constant
50
ohm
resistive
load
to
the
exciter
so that
the
length
of
coaxial
cable
connecting
the
exciter
to
the
NCL-
2000
is
not
critical
and
no
special
matching
devices
or
cable
lengths
are
necessary.
2.9
RF
EXCITER
CONNECTION
(Separate
Transmitter
and
Receiver
with
External
Antenna
Transfer
Relay)
(See
Figure
3)
When
a
separate
transmitter
and
receiver
are
used
with
their
own
separate
antenna
transfer
re-
lay,
a
direct
connection
may
be
made
from
the
antenna
connection
of
the
separate
relay
to
the
NCL-2000
coaxial
jack
labeled "
XCVR"
and
oper-
ation
will
be
identical
to
that
described
in
para-
graph
2.8.
2.10
RF
EXCITER
CONNECTION
(Separate
Transmitter
and
Receiver
Without
External
Antenna
Transfer
Relay)
(See
figure
4)
The
NCL-2000
has
been
equipped
with
a
sep-
arate
receiver
output (
RCVR)
and
transmitter
in-
put (
XMTR) .
The
receiver
output
is
connected
through
the
antenna
switching
relay
of the
NCL-
2000
so
that
the
antenna
will
be
connected
to
the
receiver
during
receiving
periods
and
disconnected
from
the
receiver
during
transmitting
periods.
The
transmitter
input
is
directly
connected
to
the
input
circuit
of
the
NCL-2000
at
all
times.
When
this
connection
is
used,
the
linear
plate
power
must
always
be
ON
to
provide
proper
operation.
In
the
event
that
the
linear
plate
power
is
re-
moved,
the
receiver
will
perform
normally
but
the
transmitter
output
will
not
be
connected
to
the
antenna
line.
Therefore,
it is
not
possible
to
op-
erate
the
separate
transmitter
and
receiver
without
the
linear
under
these
conditions.
2.11
RELAY
CONNECTION:
Automatic
transmit-
receive
operation
of
the
NCL-2000
is
afforded
by
energizing
the
NCL-2000
antenna-
transfer
relay
during
transmitting
periods
by
connecting
together
the
relay
terminals
on
the
rear
apron
of
the
linear
chassis.
Most
transceivers,
transmitters
and
receivers
have
such
switching
con-
tacts
available.
The
NCL-2000
relay
terminals
should
be
connected
to
the
normally
open (
on
receive)
terminals
available
on
the
exciter.
Since
the
current
through
the
transfer
relay
is
small, "
zip
cord"
or
hook-up
wire
may
be
used
for
this
con-
nection.
2.12
GROUND
CONNECTION:
It
is
strongly
recommended
that
the
chassis
of
the
NCL-2000
be
grounded
to
a
cold
water
pipe
or
a
good
earth
ground,
as
well
as
to
other
equipment
in
the
station.
A
stud
is
provided
on
the
rear
apron
of
the
chassis
for
this
ground
connec-
tion.
If
the
ground
is
inadequate,
the
chassis
of
the
linear
may
be "
hot"
with
RF,
which
can
cause
operating
difficulties
and
danger
to
the
operator.
If
this
occurs,
check
the
ground
connections
and
change
the
ground
location
until
satisfactory
op-
eration
is
obtained.
6
NCL-2000
NCX-3
OR
NCX-5
ANTENNA
C
ANT
I>
TO ALC
INPUT
NCL-
2000
RC
yR
NCL-
2000
CONNECTIONS
FOR
USE
WITH
A
TRANSCEIVER
FIGURE
2
RELAY
TERMINALS
CLOSED
ON TRANSMIT
TRANSMITTER
RECEIVER
EXT
ANTENNA
RELAY
ACTUATED
BY
TRANSMITTER
CONNECTIONS
FOR
USE
WITH
A
SEPARATE
TRANSMITTER
AND
RECEIVER
USING
AN
EXTERNAL
ANTENNA
RELAY
e '
ANTENNA
)
ycyR
mift
rm.
GNOALCQ
0 0
L.
-)
FIGURE
3
TRANSMITTER
RECEIVER
ALC
OLA
AN
RELAY
TERMINALS
CLOSED
ON
TRANSMIT
CONNECTIONS
FOR
USE
WITH
A
SEPARATE
TRANSMITTER
AND
RECEIVER
FIGURE
4
7
SECTION
3
OPERATION
3.1
EXPLANATION
OF
CONTROLS:
The
main
power
switch,
labeled
ON -
OFF,
energizes
filaments,
the
grid
bias
supply,
the
blower
and
the
60-
second
time
delay
that
prevents
applic-
ation
of
grid drive
and
plate
and
screen
voltage
until
the
tubes
are
fully
warmed
up.
When
the
main
switch
is
pushed,
the
green
ON
lamp
will
light,
and
approximately
one minute
later,
the
ivory
READY
lamp
will
light
indicating
the
tubes
are
warmed
up
and
plate
power
may
be
applied.
The
plate
power
switch
is
a
center
neutral,
momentary -
each -
side -
of -
center,
switch,
labeled
PLATE-
OFF,
which
operates
the
latching
type
plate
relay.
After
the
READY
lamp
is
on,
plate
power
may
be
applied
by
pushing
the
switch
up
and
releasing
it.
The
red
PLATE
light
indicates
that
the
plate
and
screen
supplies
are operating.
The
CW-SSB
switch
changes
the
plate
voltage
under
load
from
about
1800
volts
in
the
CW
posi-
tion
to
2500
volts
in
the
SSB
position.
The
screen
voltage
also
changes
from
290
to
400
volts.
This
allows
selection
of
1000
watt
operation
for
tune-up,
CW
and
RTTY
or
2000
watt
PEP
operation
for
SSB.
The
MULTIMETER
switch
allows
measure-
ment
Of the
following
parameters
as
read
on
the
multimeter:
Plate
voltage
0-5000
volts,
screen
cur-
rent
0-50
ma., grid
current
0-50
ma.,
and
exciter
tune (
relative
output)
0-50
ma.
When
the
MUL-
TIMETER
switch
is
in
the
EXCITER
TUNE
position,
and
the
amplifier
plate
voltage
is
off,
power
from
the
exciter
is
applied
to
the 100
watt
input
swamping
resistor
in
the
NCL-2000
which
then
acts
as
a
dummy
load
for
optimum
tune-up
of
the
exciter.
Relative
exciter
output
power
is
in-
dicated
as
final
grid
current
on
the
multimeter
and
the
exciter
is
adjusted
for
maximum
multi-
meter
indication.
This
unusual
feature
of
the
NCL-
2000
allows
optimum
independent
adjustment
of
the
exciter
without
the
usual
necessity
for
a
sep-
arate
dummy
load
or
the
alternative
procedure
of
attempting
to
simultaneously
adjust
both
the
amp-
lifier
and
the
exciter.
3.2
PRELIMINARY
ADJUSTMENT:
-
CAUTION -
DO
NOT
ATTEMPT
TO
TURN
ON THE
NCL-2000
OR
TO
OPERATE
ITS
SWITCHES
OR
CONTROLS
UNTIL
YOU
READ
AND
COMPLETELY
UNDERSTAND
THE
FOL-
LOWING
PARAGRAPHS.
EXPENSIVE
DAM-
AGE
MAY
RESULT
IF
THE
NCL-2000
IS
IM-
PROPERLY
CONNECTED
TO
OTHER
STA-
TION
EQUIPMENT
OR
IMPROPERLY
OP-
ERATED.
Carefully
double-check
to
make
certain
that
the
power
cable
is
wired
correctly
for
your
power
source,
that
the
proper
coaxial
cable
connections
are
made
between
the
NCL-2000
and
your
antenna
and
exciter
and
that
the
proper
connections
are
made
between
the
NCL-2000
relay
terminals
and
the controlling
terminals
on
the
exciter.
If
a
high
power
dummy
load
is
available,
it
is
strongly
sug-
gested
that
initial
adjustment
and
tune
up
be
made
with
the
dummy
load
instead of
the
antenna.
Tune-up
of the
NCL-2000
quickly
becomes
second
nature
and
may
be
totally
accomplished
when
changing
bands
within
15
or
30 seconds
after
a
little
practice,
but
until
complete
familiarity
is
achieved
it is
wise
to
go
only
one
step
at
a
time,
removing
drive
and/or
amplifier
plate
voltage
after
each
step
so
that
you
have
time
to
relax
and
review
previous
steps
without
worry.
3.2.1
PRELIMINARY
CONTROL
SETTINGS.
CHECKS
AND
ADJUSTMENTS:
1.
Turn
on
exciter
and
allow
it
to
warm
up
in
standby
or
receive
mode.
2.
Set
NCL-2000
controls
as
follows:
a.
POWER:
OFF
b.
PLATE:
OFF
c.
CW-SSB
Switch:
CW
d.
BAND:
to
desired
band
e.
PA
TUNE
and
LOAD:
to
approx-
imate
setting
in
Figure #
5
f.
MULTIMETER:
PLATE
VOLTAGE
3.
Insert
NCL-2000
power
plug
into
power
source
and
press
power
switch
to
ON.
The
green
ON
lamp
will
light,
as
well
as
the
two
rear-
illuminated
meters.
Check
to
see
whether
the
blower
is
operating.
Note:
The
blower
operates
at
all
times,
not
just
when
plate
power
is
applied.
8
4.
After
approximately
one
minute,
the
ivory
READY
lamp
will
light,
indicating
that
the
time
delay
relay
is
operating
and
plate
voltage
may
now
be
applied.
The
READY
lamp
remains
lit
once
the
time
delay
relay
has
closed.
5.
Press
the
PLATE-
OFF
switch
to
PLATE.
The
red
PLATE
lamp
will
light
and
the
multimeter
should
read
2000
volts.
6.
Press
the
CW-SSB
switch
to
SSB.
The
multimeter
should
now
read
3000
volts.
No
plate
current
will
be
indicated
on
the
plate
meter
since
the
output
tubes
are
cut
off
when
the
exciter
is
in
the
receive
mode.
7.
Press
the
PLATE-
OFF
switch
to
OFF,
and
put
exciter
in
transmit
mode.
Adjust
ex-
citer
for
zero
output
in
transmit
mode,
preferably
by
depressing
push-
to-
talk
switch
with
microphone
gain
backed
down,
or
with
the
NCX-3,
by
placing
the
function
switch
in
the
CW
position
and
depressing
the
key
with
the
carrier
com-
pletely
balanced
out.
8.
Return
exciter
to
receive
mode,
and
press
the
NCL-2000
PLATE-
OFF
switch
to
PLATE
with
the
CW-SSB
switch
still
in
the
SSB
position.
Put
exciter
in
transmit
mode
with
zero
output
as
above.
You
should
hear
the
NCL-2000
antenna
trans-
fer
relay
click,
and
idling
plate
current
should
now
be
indicated
on
the
plate
meter.
9.
Adjust
the
rear
panel
BIAS
ADJUST
control
for
225-250
ma.
idling
plate
cur-
rent.
10.
Return
exciter
to
receive
mode,
press
CW-
SSB
switch
to
CW,
and
press
PLATE-
OFF
switch
to
OFF.
Check
for
proper
straight
through
operation
of
the
driver
trans-
ceiver
or
transmitter-
receiver.
This
com-
pletes
the
preliminary
checks
and
adjust-
ment
of
the
NCL-2000.
-
CAUTION -
DO
NOT
OPERATE
THE
NCL-2000
WITH
BADLY
MISMATCHED
ANTENNAS
OR
WITH
NO
ANTENNA
CONNECTED,
SINCE
EXPEN-
SIVE
DAMAGE
TO
THE
NCL-2000
TANK
CIR-
CUIT
WILL
OCCUR.
IT
IS
NOT
ADVISABLE
TO
SWITCH
THE
MULTIMETER
TO
EXCITER
TUNE
WHILE
THE
UNIT
HAS
BOTH
PLATE
VOLTAGE
AND
FULL
DRIVE
APPLIED
SINCE
A
MO-
MENTARY
NO-LOAD
CONDITION
OCCURS
WHEN
THE
ANTENNA
RELAY
THROWS,
WHICH
MAY
CAUSE
A
MOMENTARY
ARC
-
OVER
IN
THE
PLATE
CIRCUIT
3.3
CW
TUNE-UP
PROCEDLRE:
1.
Set
Controls
as
in
paragraph
10
above.
2.
The
exciter,
whether
transceiver
or
trans-
mitter-
receiver
combination,
should
now
operate
conventionally
as
a
low
power
station
when
either
the
NCL-2000
pri-
mary
power
or
plate
power
switch
is
off,
except
when
the
MULTIMETER
switch
is
in
the
EXCITER
TUNE
position
or
when
no
separate
antenna
transfer
relay
is
used
with
a
transmitter-
receiver
com-
bination
as
noted
in
paragraph
2.10.
3.
Place
MULTIMETER
switch
in
EXCI-
TER
TUNE
position (
PLATE-
OFF
switch
still
OFF).
Place
the
exciter
in
the
transmit
mode.
You
should
hear
the
NCL--2000
antenna
transfer
relay
click,
indicating
that
the
ex-
citer
output
has
been
switched
from
the
antenna
to
the
100
watt
input
resistor
in
the
NCL-2000
which
will
now
act
as
a
dummy
load
providing
optimum
exciter
adjustment.
4.
Place
the
exciter
in
the
transmit
mode
and
adjust
it
for
normal
CW
loading
and
out-
put
as
indicated
on
the
NCL-2000
multi
-
meter,
which
is
reading
0-50
ma.
grid
cur-
rent
in
the
EXCITER
TUNE
position.
At
least
15
ma.
should
be
indicated.
If
not,
check
for
proper
exciter
operation
or,
if
necessary,
adjust the
tap
on
the
NCL-
2000
input
resistor
per
paragraph
5.7.
5.
Adjust
the
exciter
so
that
CW
output
may
be
varied
continuously
from
zero
to
full
output by
insertion
of
more
or
less
carrier
in
the
CW
mode
in
equipment
such
as
the
NCX-3
and
the
NCX-5,
or
by
what-
ever
means
is
available.
It
may
be
found
easiest
in
some
equipment
to
detune
an
early
transmitter
stage.
6.
Note
carefully
that
the
NCL-2000
screen
current
will
be
your
most
valuable
tuning
and
loading
indication
during
the
follow-
ing
steps.
The
object
of
the
tune-up
pro-
cedure,
as
you
will
see,
will
be
to
strike
the
proper
balance
between
plate
current,
drive,
and
screen
current
for
maximum
output.
Excessive
screen
current (
above
25
ma.)
indicates
insufficient
loading,
and
in
addition,
the
screen
current
will
act
as
an
extremely
accurate
indication
of
plate
circuit
tuning
by
reading
maximum
at
resonance.
The
NCL-2000
is
so
designed
that
maximum
efficient
output
may
be
accurately
determined
by
proper
adjust-
ment
of
plate
and
screen
current.
In
the
following
CW
tune-up
procedure,
the ob-
jective
is
to
achieve
a
plate
current
at
resonance
of
550
to
650
ma.
with
10-25
ma.
9
of
screen
current.
Remember,
screen
cur-
rent
will
increase
with
light
loading,
and
will
decrease
as
the
NCL-2000
is
loaded
more
heavily.
Screen
current
will
be
max-
imum
at
resonance.
CAUTION
AT
NO
TIME
SHOULD
SCREEN
CUR-
RENT
BE
ALLOWED
TO
EXCEED
40
MA.
BECAUSE
OF
THE
DANGER
OF
EXCESSIVE
SCREEN
DISSIPATION.
7.
Adjust
the
exciter
for
minimum
output
in
the
transmit
mode,
and
then
place
the
exciter
in
the
receive
mode.
Move
the
MULTIMETER
switch
to
SCREEN
CURRENT
and
adjust
PA
TUNE
and
PA
LOAD
to
approximate
settings
shown
in
figure
5.
8.
Press
the
plate
switch
of
the
NCL-2000
to
ON
and
then
place
the
exciter
in
the
transmit
mode.
Increase
drive
from
the
exciter
until
the
NCL-2000
plate
meter
reads
approximately
200
ma.
Quickly
ad-
just
the
PA
TUNE
control
for
a
plate
current
dip
while
observing
the screen
current.
9.
If
there
is
a
screen
current
indication,
you
will
note
that
it is
maximum
when
the
amplifier
is
in
resonance
and
there
is
a
plate
current
dip.
If
there
is
no
screen
current
indication,
increase
drive
from
the
exciter
until
screen
current
is
10
to
25
ma.
at
amplifier
resonance.
Note
that
as
the
PA
LOAD
control
is
increased
so
that
the
amplifier
is
loaded
more
heavily,
plate
current
increases
at
resonance,
or
plate
current
clip,
and
screen
current
decreases.
10.
At
this
point
you
should
note
plate
cur-
rent of
approximately
500
to
650
ma.
and
screen
current
of 10
to
25
ma.
CAUTION
AT
NO
TIME
DURING
TUNE-UP
OF
THE
NCL-2000
SHOULD
THE
AMPLIFIER
BE
AL-
LOWED
TO
REMAIN
OUT
OF
RESONANCE
FOR
MORE THAN
A
FEW
SECONDS.
11
Return
the
exciter
to
the
receive
mode
and
review
the
following
before
proceeding
further:
Plate
and
screen
current
in
the
NCL-2000
depend
upon
the
amount
of
drive
supplied
from
the
exciter,
as
well
as
upon
the
adjustment
of
the
PA
TUNE
and
PA
LOAD
controls.
To
adjust
drive
correctly,
and
thus
eliminate
this
variable
from
the
tune-up
procedure,
the
amount
of drive
will
be
increased
from
the
exciter
while
monitoring
plate
and
screen
current
until
an
increase
in
drive
does
not
result
in
an
increase
in
plate
current.
This
amount
of
drive
from
the
exciter
is
the
correct
amount
for
proper
final
tune-up
of
the
amplifier.
12.
Return
the
exciter
to
the
transmit
mode
and
increase
drive
while
monitoring
screen
current
to
the
point
where
further
drive
from
the
exciter
does
not
result
in
an
in-
crease
in
plate
current.
Adjust
PA
TUNE
and
PA
LOAD
controls
of
the
NCL-2000
during
this
process
to
keep
screen
current
(at
resonance)
between
10
to
25
ma.
13.
Slightly
decrease
drive
from
the
exciter
to
the
point
where
NCL-2000
plate
current
begins
to
decrease.
14.
Adjust
PA
TUNE
and
PA
LOAD
for
screen
current
at
resonance
of
approxi-
mately
10
ma.
At
this
point
the
proper
amount
of
drive
is
being
supplied
to
the
NCL-2000
and
it
is
properly
tuned
and
loaded.
Plate
current
should
be
550
ma.
for
one
kilowatt
CW
operation (
550
ma.
x
1800
volts -=
990
watts) .
If
plate
cur-
rent
should
be
under
550
ma.,
the
amp-
lifier
should
be
loaded
more
heavily
(slightly
less
screen
current,
greater
plate
current) .
If
plate
current
should
be
over
the
legal
maximum
of
550
ma.,
the
am-
ount
of
drive
should
be
reduced
slightly.
15.
This
completes
the
tune-up
of
the
NCL-
2000
for
one
kilowatt
CW
operation.
Re-
turn
exciter
to
receive
mode.
It
may
be noted
that
the
8122
tubes
in
some
NCL-2000
amplifiers
are
driven
so
easily
that
with
a
resonant
plate
current
of
550
ma.,
the
amplifier
is
still
not
fully
loaded.
This
condition
will
be
ap-
parent
in
that
the
grid
current
will
be
much
less
than
15
ma.,
with
loading
and
drive
adjusted
for
550
ma.
plate
current,
and
it
will
be
possible to
drive
hard
enough
to
exceed
the
nominal
25
ma.
maximum
screen
current.
In
such
instances,
the
NCL-2000
should
be
loaded
more
heavily,
so
that
screen
and
grid
currents
are
both
about
15
ma.,
with
the
screen
current
peaked
and
the
plate read-
ing
slightly
higher
than
550
ma.
This
will,
assure
peak
plate
efficiency
and
proper
ALC
action,
when
the
amplifier
is
placed
in
the
SSB
mode.
3.4
SSB
TUNE-UP
PROCEDURE:
1.
Follow
CW
tune-up
steps
1
through
15
above.
2.
Press
PLATE
switch
to
OFF
and
place
CW-SSB
switch
in
SSB
position.
3.
Press
PLATE
switch
to
PLATE,
which
increases
plate
and
screen
voltages
to
al-
low
2000
watt
PEP
operation.
If
a
dummy
load
is
available (
to
prevent
putting
illegal
2000
watt
DC
signal
on
the
air),
it
is
advisable
to
briefly
recheck
the screen
current
for
proper
loading
as
follows:
4.
Place
the
exciter
in
transmit
mode,
still
adjusted
for
proper
output
as
per
para-
graph
3.3.13.
An
increase
in
screen
cur-
rent
should
be
noted,
and
the
PA
TUNE
10
and
PA
LOAD
controls
should
be
ad-
justed
to
bring
the
screen
current
at
re-
sonance
to
between
25
to
35
ma.
5.
If
a
power
output
meter
is
available,
slight
adjustment
of
PA
TUNE
and
PA
LOAD
controls
may
be
made
for
optimum
out-
put.
Under
no
circumstances
may
the
screen
current
be
allowed
to
exceed
40
ma.
6.
Press
the
PLATE
switch
to
OFF
and
adjust
the
exciter
for
SSB
operation.
If
exciter
drive
adjustment
was
performed
in
earlier
steps
by
detuning
the
EXCITER
TUNE
control
as
in
the
NCX-3
and
the
NCX-5,
place
the
NCL-2000
MULTIMETER
switch
in
the
EXCITER
TUNE
position
and
adjust
the
exciter
for
normal
maxi-
mum
CW
output
and
for
SSB
operation.
7.
Place
the
MULTIMETER
switch
in
GRID
CURRENT
position,
and
press
PLATE
switch
to
PLATE.
8.
While
speaking
into
the
microphone,
ad-
vance
exciter
audio
gain
until
the
NCL-
2000
grid
current
just
flicks
off
zero
oc-
casionally
or
until
plate
current
kicks
up
to
400
ma.
on
speech
peaks.
Plate
voltage
is
2500
volts
under
full
instantaneous
peak
current
of
800
ma.,
or
2000
watts
peak
input.
Remember
that
the
mechanical
inertia
of
the
MULTIMETER
in
the
GRID
CUR-
RENT
position
requires
strict
adherence
to
the
instructions
concerning
grid
current
indication
during
SSB
operation.
When
the
GRID
CURRENT
meter
just
oc-
casionally
flickers
off
zero
on
voice
peaks,
the
NCL-2000
is
being
properly
operated.
Should
the
NCL-2000
be
driven
so
hard
that
there
is
a
constant
grid
current
in-
dication,
no
matter
how
small,
actual
peak
grid
current
will
be
excessive
and "
flat
-
topping"
and
consequent
splatter
will
oc-
cur.
CAUTION
YOUR
NCL-2000
IS
A
MAXIMUM
KILO-
WATT
IN
EVERY
SENSE
OF
THE
WORD.
UNDER
THE
ABOVE
CONDITIONS
YOUR
POWER
IS
A "
DC"
KILOWATT,
2000
WATTS
PEAK.
INCREASE
IN
MICROPHONE
GAIN
SO
THAT
SPEECH
PEAKS
EXCEED
400
MA.
MAY
RESULT
IN
FLAT-
TOPPING
AND
SPLATTER
AS
WELL
AS
ILLEGAL
EXCES-
SIVE
POWER
INPUT.
9.
If
your
exciter
contains
an
ALC
input
and
it
has
been
connected
to
the
NCL-2000,
microphone
gain
should
be
advanced
until:
a.
the
exciter
ALC
indication
is
correct,
or
b.
speech
peaks
reach
400
ma.
on
the
NCL-2000
plate
current
meter.
3.5
AM
TUNE-UP
PROCEDURE:
For
AM
operation,
adjust
the
NCL-2000
for
SSB
operation
as in
steps
1
through
7
above,
and
increase
exciter
carrier
output
until
400
ma.
of
plate
current
is
indicated
by
the
NCL-2000
plate
milliameter.
Increase
the
exciter
audio
gain
until
the
NCL-2000
plate
current
flickers
slightly
upward
on
voice
peaks,
and
then
reduce
exciter
audio
gain
to
just
below
this
point.
TABLE
OF
NCL-2000
CONTROL
SETTINGS
FOR
50
OHM
LOAD
FREQUENCY
P.
A.
TUNE
P.
A.
LOAD
Approximate
Actual
Approximate
Actual
3.50
MC.
25
30
3.75
MC.
45
50
4.00
MC.
60
65
7.00
MC.
20
35
7.30
MC.
40
50
14.00
MC.
40 40
14.35
MC.
45 45
21.00
MC.
65 50
21.45
MC.
70 55
28.00
MC.
80 55
29.70
MC.
90
60
The
above
tables
are
based
on
average
NCL-2000
control
settings
when
operated
into
a
purely
resistive
50-
ohm
load.
They
will,
of
course,
vary
with
many
installations
and
it
is
suggested
that
you
note
in
the
appropriate
column
the
final
control
settings
required
for
use
with
your
own
antenna
to
facilitate
faster
initial
adjustment
when
changing
bands.
FIGURE
5
11
SECTION
4
THEORY
OF
OPERATION
4.1
CLASS
OF
OPERATION:
Modern
linear
amplifiers
are
typically
op-
erated
in
Class
B, Class
AB
',
or
Class
AB
2
service.
The
Class
B
amplifier
has
the
distinct
advant-
age
of
drawing
negligible
current
and
dissipating
no
power
when
no
drive
is
present.
It
also
has
the
ad-
vantage
of
relatively
high
efficiency,
particularly
when
operated
with
grid
current
flow
and
with
grids
driven
well
into
the
positive
region.
The
Class
B
amplifier
does, -
however,
have
the
disad-
vantage
of
being
relatively
non-linear
because
of
non-
linearity
of
the
amplifier
tube
characteristics
in
the
cut-off
region.
This
will,
of
course,
vary
with
the
type
of
tube
selected
for
the
amplifier.
A
second (
less
well-known)
disadvantage
of
the Class
B
amplifier
appears
when
excessive
drive
is
avail-
able
and
the
linear
is
heavily loaded.
Under
these
conditions,
increasing
input
will
drive
the
grid,
screen,
and
plate
currents
to
higher
and
higher
levels
and
the
amplifier
stage
can
be
easily
dam-
aged.
Class
AB
I
operation
overcomes
these
disad-
vantages.
By
allowing
idling
current,
the
effects
of
non-
linearity
near
cut-off
are
avoided,
thus
causing
a
reduction
in
amplifier
distortion.
By
definition,
the
Class
AB
i
amplifier
does
not
draw
grid
current
and
the
grid
bias
supply
can
have
rela-
tively
poor
regulation (
or
high
internal
impe-
dance).
In
the
event
of
over-
drive,
the
amplifier
tubes
will
draw
grid
current
and
make
the
bias
voltage
more
negative.
The
result
is
effective
limit-
ing
of
plate
and
screen
currnts
to
safe
operating
levels
even
under
conditions
of
severe
over-
drive.
Unfortunately,
these
advantages
of
ABI
operation
are
only
gained
with
a
loss
of
amplifier
efficiency.
The
Class
AB
amplifier
operates
with
the
saine
idling
current
as
the
AB
I
amplifier,
and
therefore
offers
the
same
low
distortion
and
excel-
lent
linearity,
providing
a
well-
regulated
bias
supply
and
sufficient
driver
power
are
available.
The
well-
regulated
bias
supply
is
necessary
to
pre-
vent
change
in
bias
voltage
as
the
grids
are
driven
positive.
The
ability
to
drive
the
grids
positive
offers
the
important
advantage
of
higher
efficiency
than
the
Class
AB
1
amplifier.
However,
the
pre-
sence
of
the
necessary
well-
regulated
bias
supply
presents
the
same
disadvantage
apparent
in
the
Class
B
amplifier —
increasing
input
may
result
in
dangerously
high
grid,
screen
and
plate
currents.
The
NCL-2000
operates
in
grid-
current-
limited
Class
AB
2
—
a
National
development (
patent
pend-
ing)
which
combines
the
advantages
of
Class
AB
2
operation
in
terms
of
high
efficiency
and
linearity
with
the
effective
limiting
of
plate
and
screen
cur-
rents
typical
of
the
Class
ABI
amplifier.
This
is
accomplished
by
the use
of
an
electronically
series-
regulated
grid
bias
supply
designed
to
hold
con-
stant
grid
bias
with
normal
driving
levels,
but
which
allows
grid
bias to
abruptly
increase
when
grid
current
exceeds
the
pre-
determined
value
of
15
ma.
The
NCL-2000
bias
supply
has
a
constant
15
ma.
bleed.
When
grid
current
flows,
it
causes
the
regulator
output
current
to
decrease
toward
zero;
and
when
the
grid
current
reaches
15
ma.,
the
amount
of
the
bleed,
there
is
no
longer
any
current
flow
in
the
series
regulator
and
the
circuit
loses
regulation.
As
more
drive
is
applied
beyond
this
point,
grid
voltage
will
become
more
negative
and
plate
current
is
limited
just
as
in
Class
AB
i
opera-
tion.
4.2
GRID
BIAS
SUPPLY:
The
grid
bias
supply
is
a
conventional
lull
-
wave
center-
tapped
circuit
using
rectifiers
CR1
and
CR2
and
filtering
network
R36
and
C6.
Output
of
this
supply
is
fed
to
the
collector
of
the
series
regulator
transistor
Ql.
Operating
bias,
in
turn,
is
obtained
from
the
emitter
of
the
regulating
transistor.
The
15
ma.
bleed
is
obtained
through
R40,
R41
and
R42.
A
sample
of
the
output
volt-
age
is
obtained
from
the
bleed
network
and
applied
to
the
base
of the
control
transistor
Q2.
The
collector
of
the
control
transistor
is
fed
through
resistor
R38
from
the —
80
volt
supply
and
the
emitter
of
the
control
transistor
is
returned
to
ground
through
zener
diode
CR9.
This
zener
diode
is
kept
in
its
regulating
range
by
current
through
resistor
R39
from
the
negative
supply.
When
the
grids
of the
final
amplifier
draw
current,
the
bias
voltage
will
tend
to
go
more
negative.
This
will
result
in
a
negative
change
at
the
base
of
the
control
transistor
and
will
result
in
more
collector
12
current
flow
through
Q2.
This
will
make
the
base
of
the
regulator
transistor
go
more
positive,
which
results
in
less
current
flow
through
the regulator
in
such
a
manner
as
to
cancel
any
change
of
bias
to
the
final
until
grid
current
exceed
15
ma.
and
the
regulator
can
no
longer
function.
Adjustment
of
R41,
the
bias
potentiometer,
will
result
in
a
variation
of
bias
from —
25
to —
45
volts
to
set
pro-
per
idling
current.
4.3
INPUT
CIRCUIT:
Input
power
from
the
exciter
is
applied
di-
rectly
to
a
50-
ohm
non-
inductive
metal
film
swamp-
ing
resistor (
R1
through
R14) .
This
swamping
re-
sistor
is
capable
of
absorbing
more
than
100
watts
continuously
for
short
periods
of
exciter
tune-up.
Nearly
all
modern
exciters
develop
in excess
of
80
watts
PEP
output
which
will
develop
excessive
driving
voltage
across
the
resistor.
Therefore,
the
NCL-2000
has
been
designed
so
that
only
one-half
of
the
voltage
across
the
resistor
is
applied
to
the
final
amplifier
grids.
When
a
low
power
20 watt
to
80
watt
peak
output
exciter
is
used
to
drive
the
NCL-2000,
an
internal
re-
connection
may
be
made
to
provide
the
full
driving
voltage
of the
exciter
to
the
final
grids (
See
paragraph
5.7
under
Service
Instructions) .
The
low
resistive
impedance
of
the
NCL-2000
input
circuit
presents
a
constant
load
to
the
exciter
even
under
peak
signal
conditions,
so
that
operation
in
Class
AB2
service
does
not
re-
sult
in
non-
linearity
due
to
poor
exciter
regula-
tion.
Also,
this
low
resistive
grid-
to-
ground
impe-
dance
eliminates
the
need
for
neutralization
and
results
in
an
amplifier
that
is
extremely
stable
under
all
operating
conditions.
The
use
of
this
grounded-
cathode
tetrode
circuit
with
a
swamped
grid
input,
instead
of
the
more
common
grounded-
grid
circuit,
prevents
tuning
of
the
final
from
af-
fecting
tuning
of
the
exciter,
allows
lower
driving
power,
and
provides
maximum
useful
power,
since
the
exciter
power
does
not
have
to
be
added
to
the
amplifier
power
when
input
power
measurements
are
made
to
assure
legal
operation.
4.4
ALC:
The
RF
input
signal
is
coupled
to
the
8122
grids
through
capacitors
C21
and
C30.
Bias
is
supplied
to
the
grids
through
L5
and
metering
re-
sistor
R15.
Excessive
drive
applied
to
the
final
tubes (
modulation
peaks
producing
more
than
15
ma.
of
grid
current)
will
cause
an
audio
voltage
to
appear
on
the
bias
circuit.
This
voltage
is
coupled
through
C19
to
voltage
doubler
rectifiers
CRIO
and
CR11
to
develop
negative
DC
voltage
for
use
as
ALC
information.'This
may
be
fed
back
by
means
of
output
jack
J5
to
exciters
provided
with
ALC
input
circuits
capable
of
accepting
neg-
ative
ALC
voltage.
4.5
OUTPUT
CIRCUIT:
The
plate
circuit
of
the
8122
final
tubes
is
a
conventional
pi-
network.
High
voltage
is
supplied
through
plate
choke
L2
and
the
output
circuit
is
isolated
from
this
plate
voltage
by
blocking
cap-
acitor
C48.
The
PA
tune
capacitor
C42
is
a
double
section
unit.
The
smaller
section
of
this
capacitor
is
in
the
pi-
network
at
all
times
and
the
remaining
section
is
used only
on
the
80
meter
band
to
provide
full
coverage.
In
addition,
a
100
pf.
capacitor
C45
is
switched
into
the
input
to
provide
additional
tuning
capacity
on
80
and
40
meters.
The
pi-
network
coil
is
tapped
by
means
of
the
bandswitch
for
operation
on
80
through
10 meters.
The
PA
load
capacitor
C43
is
used
on
all
bands,
and
the
additional
load
capacitor
C47
is
used
on
80 meters
together
with
C46
which
is
also
used
on
40
meters
to
allow
matching
loads
from
40
to
60
ohms.
Plate
voltage
is
developed
by
a
full
wave
volt-
age
doubler
using
rectifiers
CR7
and
CR8.
Filter-
ing
is
accomplished
by
a
bank
of
electrolytic
cap-
acitors
C32
through
C39.
Screen
voltage
is
de-
veloped
by
a
full
wave
bridge
circuit
operating
from
another
winding
on
the
plate
transformer,
and
screen
filtering
is
accomplished
by
choke
L2
and
capacitor
C31.
Resistors
R18, R19,
R24
and
R43
provide
for
short
circuit
surge
limiting
in
the
plate
and
screen
circuits
of
the
final
amplifier.
4.6
METERING:
The
negative
return
of the
high
voltage
supply
is
connected
through
a 1
ampere
overload
relay
and
a 1
ohm
metering
resistor
to
ground.
A 0
to
1
volt
DC
meter
connected
in
parallel
with
the
1
ohm
metering
resistor
provides
continuous
plate
current
measurement.
A
separate
1
volt
Multimeter
is
connected
through
the
MULTIMETER
switch
to
the
multiplier
resistors
R20
through
R23
for
0
to
5
KV
plate
voltage
measurement,
to
resistor
R16
for
screen
current_
measurement
or
to
resistor
R15
for
grid
current
measurement
and
exciter
tuning
indication.
4.7
PRIMARY
POWER
CIRCUITS:
Primary
power
may
be
provided
from
either
a
115-
volt,
2-
wire,
or
230-
volt,
3-
wire
line.
In
either
connection,
115
volts
is
supplied
through
the
main
power
switch
Si to the
blower
and
the
primary
of the
bias
transformer
which
also
pro-
vides
low
voltage
A.C.
for
the
final
amplifier
fila-
ments,
the
ON
lamp,
and
to
the
one
minute
time
delay
relay
and
the
control
circuits.
After
the
time
delay
relay
has
closed (
lighting
the
READY
lamp),
and
if
the
cabinet
interlock
in
the
plate
relay
ground
return
is
closed,
the
plate
power
relay
may
13
be
energized
by
pushing
plate
power
switch
S2.
The
plate
relay
in
turn
will
apply
A.C.
to
the
plate/screen
transformer
and
to
the
plate
lamp.
One
contact
of
this
plate
relay
acts
as
a
holding
contact
and
will
keep
the
plate
relay
closed
until
the
coil
circuit
is
interrupted
by
pushing
the
plate
power
switch
off.
It
may
also
be
interrupted
by
a
momentary
trip
of
the
plate
overload
relay,
by an
interruption
of
the
cabinet
interlock,
or
by
in-
terruption
of
the
primary
power
switch.
An
im-
portant
additional
interlock,
provided
in
the
high
voltage
circuit,
is
a
spring-
actuated
mechanical
shorting
bar
which
grounds
the
high
voltage
as
soon
as
the
cabinet
lid
is
opened.
4.8
CW-SSB
MODE
SELECTION:
In
single
sideband
operation,
peak
plate
cur-
rent
is
the
controlling
parameter
with
a
given
plate
voltage.
The
amplifier
must
be
capable
of
accept-
ing
proper
peak
input
at
high
efficiency
if
maxi-
mum
output
is
to
be
obtained
without
flat
top-
ping.
The
NCL-2000
is
designed
so
that
at
the
peak
input
of
2000
watts (
2500
v.
at
800
ma.),
output
efficiency
is
60%
minimum
and
peak
output
is
as
high
as
1400
watts.
In
CW
operation
it is
neces-
sary
to
operate
the
NCL-2000
at
only
1000
watts
input.
If
this
is
clone
by
operation
at
2500
v.
at
400
ma.,
the
efficiency
will
drop
and
the
power
output
will
be
less
than
optimum.
It
is
possible
to
provide
optimum
efficiency
for
1000
watt
CW
operation
by
matching
the
load
impedance
of
the
tubes
to
the
load
impedance
of
the
amplifier.
This
may
be
done
by
altering
the
plate
voltage
and
plate
current
of the
final
amplifier
tubes.
The
NCL-2000
includes
a
front
panel
switch
marked
CW-SSB.
When
thrown
to
the
CW
position,
the
plate
and
screen
voltage
on
the
8122
output
tubes
is
reduced
from
2500
v.
and
400
v.
to
1800
v.
and
290
v.
respectively.
The
amplifier
can
now
be
loaded
to
1000
watts (
550
ma.
at
1800
v.)
and
the
load
impedance
will
be
properly
matched
because
of
the
lower
plate
voltage
and
current.
The
ef-
ficiency
will
now
be
back
to
60%
minimum
and
output
will
be
in
excess
of
600
watts.
There
is
an
added
advantage
in
this
switching
arrangement.
The
NCL-2000
is
so
designed
that
if
it is
properly
loaded
to
1000
watts
in
the
CW
position,
it is
only
necessary
to
switch
to
SSB
and
the
amplifier
is
cor-
rectly
loaded
and
tuned
for
2000
watt
PEP
SSB
operation
without
the
necessity
of
tuning
up
at
an
illegal
key-
down
2000
watts.
4.9
ANTENNA AND
TRANSMIT —
STANDBY
SWITCHING:
An
internal
antenna
transfer
relay
is
incorp-
orated
in
the
NCL-2000
to
switch
the
antenna
from
the
linear
output
to
the
transceiver
or
sepa-
rate
receiver
during
receiving
periods.
When
the
plate
relay
is
energized,
power
may
be
supplied
to
this
antenna
relay
by
shorting
the "
relay"
ter-
minals
at
the
rear of
the
chassis
with
switching
con-
tacts
on
the
exciter.
During
transmitting
periods,
the "
relay"
terminals
are
shorted,
the
antenna
re-
lay
will
be
energized,
the
exciter
input
will
be
transferred
to
the
linear
input,
and
the
antenna
to
the
linear
output.
If
the
plate
power
relay
is
open,
whether
as
a
result
of
intentional
switching
or
if
primary
power
is
not
applied
to
the
amplifier,
the
antenna
relay
is
de-
energized
and
the
exciter
is
automatically
connected
directly
to
the
antenna.
4.10
STAND-BY
CUTOFF:
Idling
current
in
the
final
amplifier
tubes
is
approximately
250
ma.
for
the
pair,
which
results
in
over
600
watts
of
plate
dissipation.
It
is
undesir-
able
to
draw
this
power
during
receiving
periods.
In
addition,
current
flow
in
the
final
amplifier
tubes
will
result
in
noise
generation
which
may
be
heard
in
the
receiver.
During
transmission,
the
screen
supply
return
is
connected
to
ground
by
a
contact
on
the
antenna
relay.
While
receiving,
the
8122
screen
supply
return
is
open
and
the
screen
voltage
is
approximattely
zero.
This
disables
the
final
amplifier
tubes
and
eliminates
the
idling
cur-
rent.
14
SECTION
5
5.1
TUBE
REPLACEMENT:
The
NCL-2000 (
like
all
linears
with
paral-
leled
output
tubes)
requires
matched
tubes
for
ef-
ficient
operation.
Should
one
of
the
output
tubes
fail,
it
is
neces-
sary
to
match
its
replacement
to
the
remaining
good
tube.
This
may
be
done
by
measuring
the
grid
bias
voltage
of
the
good
tube
at
rated
idling
current.
Remove
the
bad
tube
and
connect
the
neg-
ative
lead
of
a
high
impedance
voltmeter
with
a
50-volt
scale
to
the
tip
jack
on
the
rear
apron
of
the
chassis.
The
other
lead
should
be
grounded.
With
the
NCL-2000
adjusted
for
no-
signal
idling
and
with
the
CW-SSB
switch
on
SSB,
adjust
the
bias
control
for
125
ma.
idling
current
as
indicated
by
the
plate
milliameter.
Read
the
voltage
at
the
tip
jack.
This
test
should
be
performed
as
quickly
as
possible
since
the
air
supply
of
the
tube
is
re-
duced
drastically
with
the
other
tube
removed.
The
National
Radio
Company
Service
Department
must
be
advised
of
this
voltage
measurement,
together
with
the
Multimeter
plate
voltage
reading
taken
at
the
same
time,
in
order
to
supply
a
properly
matched
replacement
tube.
Should
both
tubes
fail,
the
replacement
pair
will
be
automatically
matched
correctly
by
National.
Many
amplifiers
contain
tubes
on
which
a
matching
number
has
been
written,
in
which
case
it is
only
necessary
to
provide
National
with
this
number
instead
of
R-33
R-34
T-
I
L-
I
T-2
M-
I
PL-
4
LID
INTERLOCK
FIGURE
6
SERVICE
INSTRUCTIONS
making
the
above
measurement.
To
change
the
tubes,
loosen
the
wing
nuts
on
the
tube
clamps
and
the screws
holding
the
clamps
to
the
stand-off
insulator.
Carefully
remove
the
tubes
and
replace
with
the
new
ones,
then
tighten
the
wing
nuts
securely.
The
8122
output
tubes
used
in
the
NCL-2000
are
guaranteed
against
failure
for
a
period
of
90
days
from
date
of
purchase.
Tubes
will
be
replaced
under
the
terms
of
the
warranty
provided
they
are
returned
to
National
for
examination
and
such
examination
indicates
that
they
are
indeed
defec-
tive
from
causes
other
than
abuse,
mechanical
damage,
or
from
failure
resulting
from
excessive
temperature
due
to
mistuning
or
operation
out
of
rating.
5.2
FILTER
CAPACITOR
BOARD
REMOVAL:
The
filter
capacitor
board
is
held
in
place
by
the
four
sheet
metal
screws
near
the
corner
of
the
board.
It
is
not
necessary
to
disconnect
wires
to
the
board
in
order
to
remove
it
—
simply
remove
the
four
sheet
metal
screws
and
swing
the
board
free
for
examination.
5.3
CABINET
REMOVAL:
The
cabinet
is
held
in
place
by
self-
tapping
R-
4I
BIAS
ADJ
BL
-I
GND/
J-7
RCVR
BIAS
CHECK
XMTR
/
*
a
XCVR
ANTENNA
_
C-44
C-46
S-5
L-4
C-45
Q-
I
V-
I,
V-2
8122
HV
INTERLOCK
K-
I
R-43
L-3
15
screws
around
the
opening
in
the
rear of
the
cabi-
net
and
by
four
screws
in
the
bottom
of the
cabinet.
To
remove
the
cabinet,
open
the
lid
and
remove
the
high
voltage
interlock
rod.
Remove
all
of the
retaining
screws
and
pull
the
chassis
and
front
panel
forward
out
of the
cabinet.
It
may
be
convenient
to
simultaneously
exert
pressure
on
the
chassis
through
the
opening
at
the
rear
of the
cabinet.
5.4
FRONT
PANEL
AND
SIDE
GUSSET
REMOVAL:
The
side
gussets
are
held
in
place
by
the
four
screws
at
the
top
and
bottom
of the
front
panel
and
by
the
sheet
metal
screws
holding
the
gussets
to
the
side
of the
chassis.
To
remove
the
front
panel,
remove
the
cabinet,
the
side
gussets,
the
in-
terlock
socket
on
the
top
lip
of
the
front
panel,
the
knobs,
the
palnuts
on
the
MULTIMETER
switch,
BAND
switch
and
PA
LOAD
shafts,
and
the
three
screws
near
the
PA
TUNE
shaft.
Pull
the
front
panel
forward
and
remove
the
meter
mount-
ing
plate
and
the
three
pilot
light
sockets,
noting
their
relative
positions
so that
they
may
be
re-
placed
correctly.
5.5
REGULATOR
TRANSISTOR
CHANGE:
The
regulator
transistor
cases
are
insulated
from ground
by
a
very thin
mica
washer.
CAU-
TION! —
Care
must
be
exercised
to
avoid
destroy-
ing
this
insulation.
To
change
a
regulator
transis
-
R-
4I
R-
I
THROUGH
R
14
OPTIONAL
GRID
CONNECTION
L-5
C-43
CR
-
I,
CR
-2
CR
9
C-6
BL-
1
tor,
remove
the
cabinet
and
the
right
side
gusset,
unsolder
the
wires
to
the
base
and
emitter
pins
and
remove
the
screws
that
hold
the
transistor
to
the
chassis.
This
will
also
free
the
collector (
case)
connection.
Pull
the
transistor
out
of
the
chassis
and
replace
with
a
new
one
by
reversing
the
above
procedure.
Before
replacing
transistor
connections,
check
the
collector-
to-
chassis
resistance
to
see
that
the
insulation
is
intact.
5.6
AIR
SYSTEM
CLEANING:
It
is
recommended
that
the
air
system
be
cleaned
every
three
months and
more
frequently
in
dusty
locations.
Remove
the
cabinet
and
the
cover
of
the
pressurized
compartment
beneath
the
tubes.
Clean
all
areas
of
dust
accumulation
with
a
small
brush
or
with
a
household
vacuum
cleaner;
also
clean
the
inside
of
the
blower
squirrel
cage
and
the
tube
plate
radiators.
An
air
jet,
if
avail-
able,
will
speed
air
system
cleaning.
5.7
GRID
RESISTOR
TAP
CHANGE:
If
less
than
80
watts
PEP
of
exciter
power
is
available,
it
is
necessary
to
change
the
tap
on
the
grid
resistor.
Remove
the
cabinet
and
locate
the
tinned
wire
running
from
a
feed-
through bushing
on
the
pressurized
compartment
to
the
swamping
resistor
bracket
nearest
the
side
of
the
chassis.
Move
this
wire
to
the
bracket
nearer
the
center
of
the
chassis.
This
bracket
also
has
the
wire
from
the
coaxial
jack
marked "
XMTR"
connected
to
it.
S-4
C-
3I
PL
-3
PL
-2
PL
-I
CR
-3
THROUGH
CR
-6
FIGURE
7
CR
-7
CR
-8
ON
REVERSE
SIDE
S-3
S-2
C t
THROUGH
C-5
C-36
THROUGH
C-39
(C-32
THROUGH
C-35
ON
REVERSE
SIDE)
R-20,
R-
2I,
R-22
K-
3
K-2
S -
I
16
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