mechanical installation
a) HEAT DISSIPATION (VENTILATION): In common with
other electronic equipment, the HF~12 produces consider-
able heat in 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 suitability of alocation.
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, astream of air Is set in
motion which continually removes heat from the ampli-
fier. (In particular, we are mainly concerned with the
major 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 will be adversely affected.
Adequate ventilation will be provided if the amplifier is
installed in an open-back 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 back 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 aconsole, it may be
situated on an open surface or on ashelf of abookcase.
Four rubber feet are also provided so that the amplifier wi 1
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not mar the surface of furniture on which It is placed.
b) EASY ACCESS TO CONTROLS: Mount the amplifier
at aheight which will permit easy manipulation of the con-
trols. Tuner controls should be located nearby.
c) ACCESSABILITY TO PARTS: Tubes are the most fre-
quently replaced Items In electronic equipment. If the
amplifier is installed in aconsole, sufficient space should
be alloted 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 aportable 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 sufficient separation to minimize mechanical speaker
vibration reaching the amplifier. The minimum separation
Is about one foot.
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 anail to
pierce the centers of the four 5/8" diameter holes for the
controls, the 3/8" hole for the viewing of the pilot lamp,
and the two small holes for mounting the control plate, to
transfer their locations to the console panel beneath. (3)
Remove the panel template. (4) Drill the holes for the
panel controls and the pilot viewing hole (the two small
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 X3/8 wood
screws. (4) If the rubber feet have been inserted in the
bottom plate, remove them. (They may be pried out with
athin 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 far forward as possible, so
that the controls penetrate the panel holes as for as pos-
sible. (7) Place aknob on each control, pressing each
knob toward the chassis firmly so that each control shaft
enters fully into its knob. (8) Draw the chassis back evenly
and carefully until the back rims of all the knobs are equally
spaced from the control plate about 1/8". (9) With 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 the 6screws 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 adiameter of 1/4".
(14) Refasten the bottom plate to the chassis, with the
four of the six *8 X3/8 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 outline 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^8X 1" screw, with a1/2"
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.
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