8.0 E4 System Troubleshooting

8.3.4 Amplifier alarms

Each amplifier section monitors its own operation and perfor- mance. If a fault condition occurs, it is reported in the Amplifier Alarm section of the Error Log. Upper amplifier alarms affect channels 1 and 2, and Lower amplifier alarms affect channels 3 and 4.

The amplifier section of the alarm log indicates 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 approx- imately 125V. In the 100V mode, a normal rail voltage is approximately 165V.

Temperature: The internal operating temperature of the amplifier. Normally, this will be between 0 and 160 degrees Fahrenheit.

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.

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

Low Voltage

 

(>20V)

(<20V)

 

 

 

High Current

Driving an impedance <12

(>2A)

• Reduce total speaker load

 

• Check for partial short of speaker line

 

 

 

High Current

Loudspeaker trans-

Short on speaker line

(<1A)

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 impedance which is too low (<12). 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 should be replaced.

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.

Amplifier alarms – input and output status

The Input and Output Status sections display the fault condition which caused the alarm and the current status of the amplifier output.

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Bose E4 manual Amplifier alarms using output voltage and current

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