THE
MODEL
231
SIGNAL
TRACER
The Model
23
I
is
an
all
solid-state
tuned
signal tracer
of
advanced design.
It
features an active
probe
with an
input
impedance greater than 10 megohms. Band switch selection
of
fixed ceramic filters tunes the
instrument
to
any one
of
the
three common i-f frequencies. In
addition.
an
untuned
rf
input
and
an
audio
input
enable
you
to
trace a signal from the
antenna to the loudspeaker in
almost
any AM, FM, or AM/FM
receiver you might be called
upon
to
service.
If you purchased
your
signal
tracer
wired ,
turn
to page 32
and read the operating
instructions.
If
your
instrument
is
the
kit version,
you
are probably anxious
to
begin
construction,
so
let's get started.
ASSEMBLY HINTS
There
is
no satisfaction like
that
of
building a kit and having
it work perfectly the first time
you
try
it. Here are some
suggestions
that
will help
you
reach this goal.
It's a good idea
to
read over
the
entire
assembly section
before beginning actual
construction.
This way
you
get an
overall picture
of
what
is
to
be done
and
how
each stage
of
the
assembly relates
to
the others. When
you
are ready
to
begin
construction, read each step
through
and make sure you
understand what must be done.
After
you
perform
each step,
check it
off
in
the
space provided and proceed
to
the next
step.
Follow the Instructions.
Perform
each step in the exact
order given.
Don't
try
shortcuts
such
as
omitting
steps or
assembling the kit from the
schematic
diagram.
Our
experience
has shown
that
even veteran
kit
builders make wiring errors
when they fail
to
follow directions. Tracking down and
correcting wiring errors in
completed
kits can be a tedious and
time-consuming process. By far,
the
quickest
shortcut
is
to
follow the assembly
instructions
to
the
letter.
Do a
Good
Soldering
Job.
Poor
soldering
is
the greatest
single cause
of
problems in
completed
units. Most
of
the
soldering in this kit will be done
on
a
printed
circuit board.
This makes it easy
to
do a professional-looking
construction
job
without
being a professional.
You
will need a small pencil
soldering iron.
To
mount
components
on the
circuit
board,
first bend the
leads
to
fit the holes in the
board
using
your
longnose pliers.
Next, pass the leads
through
the
holes and press the
component
down until it rests squarely
on
the surface
of
the
board. You may
bend
the leads
on
the
other
side
of
the
board
slightly
outward
so
that
the
component
stays
put
when you
turn the board over for soldering.
To
solder the
component
leads
to
the foil pads, apply the
tip
of
the iron so .that it
touches
both
the lead and the foil. At
the same time, feed
the
end
of
the solder
to
the lead and the
foil until a small
mound
of
molten
solder surrounds the lead
and covers the pad. When this happens, withdraw the solder
and then the iron.
After the solder has solidified, clip
off
the lead close
to
the
solder
mound
with
your
diagonal cutters. When soldering
components
on the circuit
board,
watch
out
for solder bridges
that
cause short circuits. Each time
you
solder a connection,
make sure
that
the solder
mound
covers only
that
connection
and does
not
run over
to
a
nearby
pad or foil path.
When
you
connect
wires and
components
to
controls and
switches
on
the
front
panel, be sure the mechanical connection
of
the wire
or
lead
to
the terminal lug
is
secure before you
solder. Do this by
hooking
the wire or lead through the
terminal lug, then crimping
it
with
your
longnose pliers before
soldering.
Each chassis wiring step will include a notation such
as
(NS),
(SI),
(S2), or
(S3).
These
notations
tell
you
whether
to
solder the
connection
made
in
that
step and,
if
so
, the total
number
of
wires
to
be
connected
at
that
point. Each time
you
make a solder
connection,
check
to
see
that
you
have the
correct
number
of
wires
connected
to
the terminal lug. The
notation
(NS) indicates
that
a
connection
should
not
yet be
soldered because
other
wires will be added. When
you
install
the last wire,
you
solder
the
terminal, and this will be
indicated
by
the
letter
S followed by a number. The
number
tells
you
how
many
leads are supposed
to
be
connected
to
the
terminal before it
is
soldered.
For
example,
if
a step says,
"Connect
a wire
to
lug 6
(S3),"
there should be three leads
connected
to
this
terminal
before it
is
soldered. In cases where
a wire
or
component
lead passes through a terminal or lug and
connects
to
another
terminal
or
lug, it
counts
as
two
leads, one
entering and one leaving
the
terminal
or
lug.
As
stated
earlier,
poor
soldering
is
the greatest single cause
of
problems in
equipment
returned
to
us
for repair. You can
greatly reduce the possibility
of
poorly soldered connections
in your signal tracer
if
you
clean the leads on the resistors and
capacitors before installing
them.
Do this by scraping the leads
lightly with a knife,
or
twisting
them
between two pieces
of
fine sandpaper. You
can
further
guard against poor soldering
by using a clean,
hot
iron at all times.
Be
sure
that
enough heat
is
applied
to
avoid rosin
joints
. This
is
of
the
utm
ost
importance.
Another
important
point
to
remember
is
to avoid using
too
much solder. Use
only
enough
to
lightly cover the leads and
terminal
you
are soldering. Let any excess solder flow
onto
the
