Specifications
mechanical installation _
a)
HEAT
DISSIPATION (VENTILATION): In common with
other
electronic
equipment,
the
HF-12 produces
consider-
ableheatin
normal
operation.
Unless continuous and
ade-
quate
air
flow is
obtained
around
the
heat
producing
ele-
ments, these
elements
will
over-heat
and
their
useful
life
will be
greatly
curtailed.
It Is useful to understand
the
process of
convection
where-
by
heat
is removed In judging
the
suitabilltyofa
location.
Air
heated
by
the
heat-producing
elements expands
and
rises; cool
air
is drawn from
beneath
to
take
the
place
of
the
heated
air.
In this
manner,
a stream of
air
Is
set
in
motion which
continually
removes
heat
from
the
ampli-
fier. (In
particular,
we
are
mainly
concerned
with
the
mcler
heat-producing
elements;
the
two EL84
output
tubes
and the EZ81
rectifier
tube.)
If
there
Is
any
impediment
to or constriction
of
the
air
flow,
the essential process
of
heat
removal wi II be
adversely
affected.
Adequate
venti
lotion
will
be provided if the
amplifier
is
installed in
an
open-bock
console
provided
that
the
top
of the
amplifier
is
spaced
at
least
two Inches below
any
shelf mounted
above
It . If
the
cabinet
is
enclosed
at
the
rear,
provide several
large
holes or slots as low down
and
as high up in
the
cabinet
bock as
possible.
As an
alter-
nate,
holes may be provided In
the
sides,
bottom,
or top
of the
cabinet.
The
important
thing to remember Is
that
effective
ventilation
requires provision for cool
air
to
en-
ter
at
the
bottom and hot
air
to
leave
at
the
top .
If the
amplifier
Is not
installed
in a
console,
it
may be
situated on an
open
surface
or on a
shelf
of a
bookcase.
Four rubber
feet
arealso
provided so
that
the
ampliflerwil
I
not mar
the
surface
of
furniture
on
which
It
is
placed.
b) EASYACCESS TO
CONTROLS:
Mount
the
amplifier
ata
height
which
will
permit
easy
manipulation
of
the
con-
trols. Tuner
controls
should be
located
nearby
.
c) ACCESSABllITY TO
PARTS:
Tubes
are
the
most
fre-
quently
replaced
Items In
electronic
equipment.
If the
amplifier is
Installed
ina
console,
sufficient
spoce
should
bealloted
to
reach
and remove
any
tube
in
the
amplifier.
Furthermore,
input
and
output
terminals of
the
amplifier
should be
accessible
to
permit
easy
interchanging
of sys-
tem components for comparison, and
connection
or
dis-
connection of a portabl e
tape
recorder
which
is stored
a-
way when
not
In
use.
If
antennas
are
strung around the
back of the
console
In
which
the
amplifier
is
installed,
arrange them so
they
will
not
interfere
with
access
to
the
amplifier.
d) ACOUSTICAL ISOLATION: If
amplifier
and
speaker
are Installed In
the
same
cabinet
(not recommended),
pro-
vide
sufficlent
seporatlon
to
minimize
mechanical
speaker
vibration
reaching
the
ampllfi
er.
The minimum
seporatlon
Is
about
one
foot.
3
CONSOLE
MOUNTING
a)
Operations
on
console
front
panel
preliminary
to
am-
plifier
mounting: (1) Tape the
panel
template
provided
to
the
face
of
the
console
so
that
the top of the mounting
surface
line
on the
template
is level
with
the
top of the
amplifier
mounting
shelf.
(2) Use an awl or a nail to
pierce
the
centers
of
the
four
5/8"
diameter
holes for the
controls,
the
3/8"
hole
for
the
vi ewing of
the
pilot
lamp,
and
the
two smaII hoIes for mounting
the
contro
I pia
te,
to
transfer
their
locations
to
the
console
panel
beneath.
(3)
Remove
the
panel
template.
(4) Dri II
the
holes for
the
ponel
controls
and
the
pilot
vi ewing hoIe
(the
two smaII
holes
which
have
been
marked
are
for wood screws).
b) Amplifier mounting in
console:
(1) Pull off
the
con-
trol knobs. (2) Remove the
control
plate,
which
is
at-
tached
to the
bezel
by two
screws.
(These may be
dis-
carded
since
they
are
unsuitable
for
attaching
the
control
plate
to the
console
panel
and
two
'4X3/8
wood screws
have
been
supplied for this
purpose.)
(3) Fasten
the
con-
trol
plate
to
the
console
panel
with
the
2
'4
X
3/8
wood
screws . (4) If the rubber
feet
have
been
inserted
in the
bottom
plate,
remove
them.
(They may be
pried
out
with
a
thin
screwdriver.
) (5) Remove
the
four screws
that
fasten
the
bezel
to
the
side
pieces
and
remove
the
bezel,
which
is not used in
console
mounting.
(6)
Place
the
unit
on
the
mounting
shelf
and
slide
it
as for forward as
possible,
so
that
the
controls
penetrate
the
panel
holes as for as
pos-
sible.
(7)
Place
a knob on
each
control,
pressing
each
knob toward
the
chassis firmly so
that
each
control
shaft
enters
fully
into its knob. (8) Draw
the
chassis bock
evenly
and
carefully
unti I the
back
rims of
all
the
knobs
are
equally
spaced
from the control
plate
about
1/8".
(9) Wi th a
sharp
pencil,
draw the outline of the
side
and
rear
bottom
edges on the chassis
shelf.
As
the
bottom
plate
falls short
of
the
full
width
by 3
/16"
on
each
side,
draw new
side
edge
lines
3/16"
inside the
original
side
edge
lines.
(10)
Now remove
the
knobs
and
take
the chassis
off
the
shelf.
(11) Remove
the6
screws
which
fasten
the
bottom
plate
to
the
chassis. (12)
Place
the bottom
plate
exactly
in the
outline
drawn on
the
shelf
and
mark the
position
of the
center
hole
on
the
left
side
and
the
center
hole
on
the
right
side.
(13) Remove the bottom
plate
and
drill
each
of the marked holes on the
shelf
to a
diameter
of
1/4".
(14) Refasten the bottom
plate
to
the
chassis,
with
the
four
of
the
six 18 X
3/8
screws previously
removed,
using
the
two holes
at
the
rear
and
the
two holes
at
the
front of
the chassis. (15)
Replace
the chassis on the
shelf,
position-
ing it
exactly
in the outl
ine
previously
drawn,
and
restore
the
knobs. This time make sure
that
the
indicator
dot on
each
knob
agrees
with
the
control
position.
(16) From the
bottom
side
of
the
shelf,
insert
a 18
XI"
screw,
with
01/2"
flat
washer
against
the
head,
through both
the
left
and
right
side
center
holes.
These screws
engage
the
stamped
nut
over
each
hole
on
the
chassis
flange
and
when
tightened
secure
the
chassis to
the
shelf
.