Ashly TRA-4150 Manuel d'utilisation - Page 10

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Operating Manual - Powerflex Multi-Channel Power Amplifier

SELF-PROTECTION FEATURES

Powerflex amplifiers contain circuitry to self-pro-

tect during extreme fault conditions. These fault condi-

tions are:

1.) Power supply undervoltage

2.) Power supply overvoltage

3.) Output overcurrent

4.) Heat sink overtemperature

5.) Unacceptable DC or high frequency output content

6.) AC power interruption

Except for AC power interruption, the detection

of any fault will result in the activation of protection cir-

cuitry on a particular module, which consists of two chan-

nels. That is, a short circuit on the output of channel 1

will result in both channel 1 and channel 2 entering pro-

tect mode. This is because the signal processing module,

which processes both channels simultaneously, does not

distinguish between the two channels within a channel pair

when processing a fault.

An AC power interruption will result in all chan-

nels entering protect mode simultaneously, just as if the

amplifier is being turned off.

In all cases, the amplifier will restart the signal

processing module after a short delay and will reconnect

the speakers after several seconds if no further fault con-

ditions exist. This allows the servo circuitry to bring any

residual DC offsets to zero before speakers are connected.

Specific conditions resulting in a fault are as follows:

8.1 Power supply undervoltage - less than about

55 volts on the either supply rail. Possible causes would

be total load on the outputs exceeding recommendations

(remove some speakers - 4

low AC mains voltage (reduce extension cord length or

increase wire size, or switch to an AC mains circuit more

capable of supporting the amplifier's power requirements),

or improper AC inlet mains voltage setting (make sure

nominal AC mains voltage matches the number in the view-

ing window on the AC inlet).

8.2 Power supply overvoltage - more than about

92 volts on either supply rail. Possible causes would be

high AC mains voltage (change to an AC mains circuit with

voltage within the amplifier's stated requirements) or im-

proper AC inlet mains voltage setting (make sure nominal

AC mains voltage matches the number in the viewing win-

dow on the AC inlet).

load min, 8

min bridged),

8.3 Output overcurrent - more than 15 to 20 amps

being drawn from any output. Possible causes would be

total load on the affected output exceeding recommenda-

tions (disconnect some speakers), or a short circuit on one

of the outputs driven by the affected module (inspect

speaker wiring for proper connection).

The above conditions are checked by the signal

processing module on a switching cycle by switching cycle

basis and are therefore monitored as often as a million or

more times a second, allowing protection well before de-

structive conditions have time to cause part failure.

8.4 Heat sink overtemperature - a measured heat

sink extrusion temperature of more than 85 to 90 degrees

C. The three-speed fan will switch to medium speed at an

extrusion temperature of 45 to 50 degrees C, and to high

speed at a temperature of 70 to 75 degrees C. The

overtemperature fault will clear itself when the measured

temperature is below about 70 degrees C. The fan will

operate at low speed below about 50 degrees C.

8.5 Unacceptable DC or high frequency output

content - a DC offset in the output signal of more than a

few hundred millivolts indicates module failure, and will

trigger a DC protect fault.

100kHz) in the output at high amplitudes can cause speaker

damage and causes a fault condition more or less rapidly

as frequency and amplitude vary.

These two conditions (DC and HF) are tested by

the same circuit so the exact cause cannot be isolated. If

the fault condition persists after disconnecting all inputs

and outputs from the amplifier, there is probably a module

failure requiring service. Note: the self-testing circuit may

take as long as 30 seconds to recover from this fault, so be

sure to give the amplifier enough time to reset itself. If

after 30 seconds the module has recovered, begin plug-

ging in one input and output at a time in an effort to iso-

late a system high-frequency or oscillation problem.

8.6 AC power interruption - a dropout (or brown-

out of sufficient magnitude) of more than one half mains

line cycle and less than one whole cycle in duration.

High frequency (20kHz to