Heathkit DX-40 User Manual

NOTE:
Due
tothe
action
ofthe
polarized
electrolytic
capacitors
the
ohmmeter
test
leads
should
be
interchanged
to
favor
the
higher
resistance
readings.
Again,
beforeapplying
power,
check
all
solder
connections,
making
sure
none
have
been
missed
and
that
all
are
good
electrical
connections.
Check
the
coax
antenna
connector
from
the
center
terminal
to
the
outside
of
the
coax
for
a
short.
It
should
check
"open".
Check
the
microphone
connector
in
the
same
manner.
It
should
also
check
"open".
TUNING INSTRUCTIONS
If
any
of
the
following
tests
cannot
be
performed
or
show
abnormal
indications,
turn
to
the
sec-
tion
of
the
manual
entitled
Service
and
Maintenance
Hints.
Set the
transmitter
up
as
follows:
crystal
switch
in
any
position
(no
crystals
or
VFO
plugged
in);
operation
switch
OFF;
drive
control
in
any
position;
bandswitch
10-11
meter
position;
antenna
tuning
"O"
position;
grid-
plate
switch
in
PLATE
position;
final
tuning
"O"
position.
Plug
the
line
cord
into
a
117-volt
AC
receptacle.
Nothing
should
happen,
if
anything
does,
pull
the
line
cord
immediately.
There
is
trouble
in
the
AC
power
circuits
which
must
be
corrected
before
proceeding.
If
operation
is
normal
so
far,
switch
the
operation
switch
to
the
STANDBY
position.
The
pilot light
and
all
tubes
should
light
but
there
should
be
no
meter
reading
or
other
indication
yet.
Switch
to
PHONE
position.
With
the
key
plugged
in
there
will
now
be
voltage
across
the
key
terminals
so
use
caution.
Depress
the
key
momentarily.
The
meter
(switched
to
PLATE
position)
should
read
between
1/2
and
full
scale.
Release
the
key.
For
the
following
adjustments
an
80-meter
crystal
in
the
range
of
3500
to
3600
or
a
40-meter
crystal
in
the
range
of
7000
to
7200
should
be
used.
A
VFO
tuned
within
these
limits
would
also
suffice.
Install
the
crystal
in
any
of
the
three
sockets
and
set
the
crystal
switch
for
this
soc-
ket
or
the
VFO
position.
Set
the
bandswitch
to
10
meters
and
connect
a
dummy
load
such
as
a
40-watt
light
bulb
from
the
ground
bolt
to
the
center
of
the
coax
connector.
Switch
the
meter
to
read
grid
current.
Set
the
operation
switch
to
STANDBY
and
plug
the
line
cord
into
a
power
source.
Set
the
loading
(antenna
tuning)
control
to
"O"
(capacitor
fully
meshed).
After
about
two
minutes
time
for
tube
warmup,
switch
to
TUNE
position,
with
the
meter
switched
to
read
grid
current,
depress
the
key
and
adjust
the
drive
control
for
maximum
grid
current
reading.
Release
the
key.
Locate
the
40-meter
oscillator
coil
adjustment
on
top
of
the
chassis
and
lubricate
it
with
one
drop
of
light
oil.
With
a
radio-TV
type
alignment
tool
or
a
small
screwdriver,
turn
the
slug
(counter-clockwise)
to
the
end
of
its
travel.
Do
not
try
to
force
it
past
this
point
to
avoid
frac-
turing
the
powdered
iron
core
slug.
Close
the
key
and
turn
the
slug
(clockwise)
until
maximum
grid
current
is
indicated.
Release
the
key.
NOTE:
This
indication
does
not
mean
that
the
oscillator
plate
coil
is
tuned
exactly
to
the
fre-
quency,
the
fact
being
that
in
some
cases
the
oscillator
provides
more
than
sufficient
drive
for
the
buffer
stage,
in
which
case
a
slight
off-tuning
of
the
oscillator
coil
results
in
an
increased
grid
current
reading
to
the
6146
final
tube.
In
general,
this
tuned
coil
should
be
adjusted
for
the
highest
reading
of
grid
current
near
the
range
of
frequencies
in
which
operations
are
planned.
Once
adjusted,
it
can
be
left
alone
as
long
as
sufficient
grid
drive
is
obtained.
On
10
meters
with
a
40-meter
crystal,
a
higher
reading
is
obtained
with
the
slug
screwed
out
farther
than
when
an
80-meter
crystal
is
used.
In
effect,
the
oscillator
is
overdriving
the
buffer
with
the
40-meter
crystal
and
detuning
the
oscillator
plate
circuit
reduces
the
excess
drive
to
the
buffer
stage.
Page 31

Heathkit DX-40 Specifications

General

Brand	Heathkit
Model	DX-40
Category	Transmitter
Language	English