Information subject to change
97-7796264_09-04-2020
7548/7794/7796/7796HC OPERATOR’S MANUAL – SECTION 7
34
7.7
Amplifier Overheats (Over Temp
Fault Condition)
There are two possible reasons why the amplifier
is overheating:
1.
Excessive Power Requirements
2.
Inadequate Airflow
7.7.1 Excessive Power Requirements
An amplifier will overheat if the required power ex
-
ceeds the amplifier’s capabilities. High duty cycles
and low-impedance loads are especially prone to
cause overheating. To see if excess power require
-
ments are causing overheating, check the follow
-
ing:
1.
The application’s power requirements fall
within the specifications of the amplifier. See
the
Specifications
section.
2. Faulty output connections and load.
3.
Undesired DC offset at the Output and Input
signal.
7.7.2 Monitoring Heat Sink Temperature
When running the amplifier in very difficult condi
-
tions, monitoring the amplifier’s heat sink tempera
-
tures can be very instructive. The amplifier has
convenient points for monitoring heat sink tem
-
peratures located on the main circuit board. See
Figure 7.5.
Connect TEMP and GND to monitor the
heat sinks responsible for positive voltages; con
-
nect across –TEMP and GND to monitor the heat
sinks responsible for negative voltages.
When running typical sine-type wave forms, read
-
ings at both monitor points should be similar. A
deviation can be an indication of a DC offset that
is causing one side of the amplifier to work harder
than the other.
To convert the monitor point voltage readings to
degrees Celsius:
Temperature in degrees Celsius = (V x 100) – 273
Where:
V = Voltage at Pin (ex. 3.73)
V x 100 = Degrees Kelvin (ex. 373.0)
–273 = Degrees Celsius (ex. 100°C)
It is recommended for most applications that long-
term amplifier heat sink temperatures be limited to
100-120°C.
7.7.3
Check for Inadequate Airflow
If the amplifier chronically overheats with suitable
power/load conditions, then the amplifier may not
be receiving adequate airflow. To check for ad
-
equate airflow, proceed with the following steps:
1.
Check air filters. Over time they can become
dirty and worn out. It is a good idea to clean
the air filters periodically with a mild detergent
and water.
2. Visually inspect fans to assure correct opera-
tion while amplifier is On.
Any inoperative, visibly slow, or reverse-spinning
fan should be replaced. Please see the Factory
Service information at the end of this section.
An OverTemp condition places the amplifier in
Standby mode. If the OverTemp pulse is ex
-
tremely short, as in the case of defective wiring or
switches, the OverTemp pulse may be too brief to
observe.
Figure 7.5 – +TEMP and -TEMP test point locations
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