Apogee APL-220, Руководство пользователя

Страница: 17 / 44

(2) Ambient Temperature
The APL-220, -500
,
and -800 are designed to be used in ambient tempera-
tures ranging from 32°F - 11 3°F (0°C - 45°C). Higher or lower temperatures
could cause system shutdown or result in early component failure. When
used outdoors on a hot day, take precautions to avoid direct sunlight on the
rear heat sink. Direct, intense sunlight can raise the temperature of the heat
sink to a point where the amplifiers may automatically shutdown to avoid
permanent damage.
(3) Convection Cooling and use in Horizontal Position
The APL-220, -500
,
and -800 are convection-cooled. The heat generated by the
internal amplifiers and power supplies is conducted to the rear heat sink and
transferred to the air by means of
natural convection . Convection occurs from the
change in density of air molecules as they are heated, creating a natural airflow
from the relatively cool bottom of the heat sink to the warmer top area. Air flows
through the cooling fins, increasing in temperature as it rises.
If the APL-220, -500
,
or -800 are used in a horizontal position, air will not
flow as readily through the fins. When placed horizontally, the fins act as
obstacles to the airflow, and cooling efficiency is reduced. In moderate ambi-
ent temperatures, this will not usually cause a problem. However, it is prudent
to test the system under maximum power conditions at the highest ambient
temperature that will be encountered, in order to verify if cooling is adequate
to prevent system shutdown. Since the temperature of the heat sink will
increase over time as the system is used, this test should be conducted for a
time period equivalent to the actual intended duration of use.
(4) More About Heating and Cooling
The APL-220, -500 , and -800 have a relatively complex thermal dynamic sys-
tem. They contain several heat sources (amplifiers, power supplies, and driv-
ers) that generate significant heat but only when program material is being
reproduced. They are cooled primarily through convection; and secondarily,
by a small degree of air movement generated by the cone drivers.
Because the heat output of the system is directly proportional to the dura-
tion and nature of the program material, the system may not reach thermal
stability for several hours after it is activated. For this reason, it is important
to test the system under actual conditions of use if questionable conditions
are present. Questionable conditions include:
(a) ambient temperature at or above the maximum rating
(b) intense sunlight or artificial light shining on the heat sink
(c) program material that runs for many hours without pause
(d) combinations of the above
1 7