Eico HF-20 - Construction Procedure; General Construction Instructions

GENERAL
INSTRUCTIONS
Core
token tn
the
construction
of
this
Instrument
will
reword
the
constructor
wlthmony
years
of
satisfactory
service
and
greater
confidence
In his
Instrument,
Weurge
you
to
not
rush
the
construction,
but
to
takeal)
the
time
necessary for
proper,
assembly
and
wiring.
Furthermore,
we
urge
strongly
that
you
follow the
wire and
parts
layout
shown
in
the
pictorial
diagrams
as
closely
as possible.
This
Is essential,
because
the
position of
wires
and
parts
is quite
critical
in
this
instrument;
changes
may
seriously
affect
the
characteristics
of
the
circuit.
UNPACKING
THE
KIT:
Unpack
the
kttcarefullyand
check
each
part against
the
parts
list
Including
those
parts
that
are mounted
to the
chassis.
If you
have
trouble
identifying
any
parts,
refer
to the
pictorial
diagrams
or
the
color
code
chart.
You may
find
that
the
value of
a
component
will vary
within
the
allowable
circuit
tolerance.
As
an
©Sample,
a
470K ohm
resistor
may have
substituted
for
it a
510K ohm
resistor
if
the
circuit
is such
as to
allow
this
substitution.
In
general,
resistors
and
controls
have a
tolerance
of ±20%
unless
otherwise
specified.
Therefore
a
100K
resistor
may
measure
anywhere
between
80K and
120K
ohms.
Tolerances
on
capacitors
are
even
greater,
unless
specified.
Limits of
+100%
and
"50%
are
usual
for
electrolytic
capacitors.
CONSTRUCTION
HINTS:
USE
THE
BEST
GRADE
OF
ROSIN
CORE
SOLDER
ONLY,
preferably
one
containing
the
new
activated
flexes
such
as
Kester
"Resin-Five",
Ersin
"Multicore"
or
similar
types.
UNDER
NO
CIRCUMSTAN-
CES
USE
ACID
CORE
SOLDER
OR
ACID
FLUX
since
acid
flux
can
cause
se—
rious
corrosion.
Before
soldering
make
certain of
a
good
mechanical
connec-
tion.
Use
a
clean,
freshly
tinned
soldering
iron,
no
smaller
than
100
watts,
and
place
the
solder
on
the
joint
(not
on the
iron)
so
that
the
solder
is melted
by
the
heat
from
the
joint
itself.
Do
not
remove
the
soldering
Iron
until
the
solder
flows
and
check
to
see
that
the
resulting
joint
is
smooth
and
shiny
when
the
solder
has
cooled.
There
are
two
extremes
to
be avoided;
too little
heat
and
too
much
heat.
If
too
little
heat
is
applied,
the
joint
will
appear
pitted
and
grey.
Indicating
a
rosin
joint
which
is unsatisfactory.
On
the
other
hand,
if
too
much
heat
is
applied
to
a joint,
the
parts
connected
to
it
may
either
change
value,
lose
their
protective
coating,
or
break
down.
If
you
are
soldering
close
to
a part,
hold
the
lead
between
the
pprt
and
the
joint
being
soldered
with
the tip
of
a
pair
of
longnose
pliers.
The
pliers
will
conduct
the
heat
away
and
prevent
the
component
from
being
unduly
overheated.
If
for
any
reason
it
is necessary
to
resolder
a
joint,
be
sure
to
use
new
solder.
It should
also
be
noted
that
the leads
on
transformers,
capacitors,
and
resistors
are
very
often
longer
than
necessary.
These
leads
should
be
trimmed
to
the
proper
length when
wiring.
CONSTRUCTION
PROCEDURE
:
The
complete
step-by-step
mounting
and
wiring
procedure
follows.
To keep
the
drawings
uncrowded,
unnecessary
rep-
etition of
mounting
or
wiring
details
may
be omitted.
Note:
The
abbreviation
(C)
means
connect
but
do
not solder
(until
other
leads
have
been
connected).
The
abbreviation
(S) means
connect
and
solder.
The
drawings
below
show
the method of
mounting
certain
specific
components
properly.
Solder lugs
are
shown
In
the
socket
mounting drawings
simply
to
Indicate
the
correct
position
of
such
a
lug
when
it
Is
specified
for
a
particular
socket.
The
mounting
drawing
for
the
hum-balancing
pot
R33,
which
must
be
Insulated
from
the
chassis,
shows
the
proper
position of
the
Insulating
shoulder
washer.
Refer
to
the
relevant
drawing
as required
during
the
mounting
pro-
cedure.
INSERT
DRAWINGS
-
FOR
FIG.
1