Bose FreeSpace Business E4 II Series Service Manual page 85

Amplifier alarms
Each amplifier section monitors its own
operation and performance. If a fault condi-
tion occurs, it is reported in the Amplifier
Alarm section of the Error Log. Upper ampli-
fier alarms affect channels 1 and 2, and
Lower amplifier alarms affect channels 3
and 4.
The amplifier section of the alarm log indi-
cates the following:
• Alarm type – The generated alarm type is
the first item.
• Amplifier status – When an alarm is
generated, the amplifier reports its current
operating status for diagnostic purposes.
The following items are reported in the
status:
Date & Time: Date and time when alarm
condition occurred.
Rail Voltage: The amplifier positive and
negative rail voltages. Normally, the amplifier
rail voltage should be between 100V and
190V. Voltages outside this range will cause
the amplifier to shut down. In the 70V mode,
a normal rail voltage is approximately 125V.
In the 100V mode, a normal rail voltage is
approximately 165V.
Temperature: The internal operating tem-
perature of the amplifier. Normally, this will
be between 0° and 160° Fahrenheit (-18° to
71° Celsius).
Output Voltage: The actual output voltage of
the amplifier at the time of the alarm.
Output Current: The actual output current of
the amplifier at the time of the alarm.
Input Status: The status of the input signal to
the amplifier. Possible status messages are
DC sense fault, amplifier module fault, AC
power fault, sleep mode, high-frequency
sense fault, and retry fault.
Output Status: The status of the amplifier
output at the time of the alarm. Possible
status messages are "amplifier module
muted," and "speaker relay off."
Fan Speed: The fan speed at the time of the
alarm.
TROUBLESHOOTING
High Current
(>2A)
High Current
(<1A)
85
Operating Mode: The current setting of the
output voltage select switch, 70V or 100V.
Amplifier alarms – using output voltage and
current
Reviewing the output voltage and current
can help to diagnose a problem. Compare
the output voltage and current for each of
the two amplifier outputs to determine the
nature of the problem.
High Voltage
(>20V)
Driving an impedance <12 Ohms
• Reduce total loudspeaker load
• Check for partial short of loudspeaker line
Loudspeaker trans -
former saturation at
low frequency
• Check for proper
Speaker EQ setting
• Set Speaker EQ to
high-pass filter
Amplifier alarms – using rail voltage
Normally, the amplifier rail voltage should be
between 100V and 190V. In the 70V mode a
normal rail voltage is approximately 125V. In
the 100V mode a normal rail voltage is
approximately 165V.
By comparing the + and – rail voltages, you
can determine if you are driving an imped-
ance which is too low (<12 Ohms). In this
case the difference between the two rails will
probably be greater than 20%. If one of the
rails shows a voltage, and the other does
not, the amplifier module should be re-
placed.
As you review all alarm records you can
compare the plus rail voltage in each of the
status sections. For example, a drop of 50%
in one status could indicate a brownout
condition occurred.
Low Voltage
(<20V)
Short on loud -
speaker line