Northern Airborne Technology PA700 - Manual (Page 29)

PA700 Series High Power Voice Amplifier
SM44 Installation and Operation Manual
Section 3 Rev: 1.00 Issue 4 Page 3-3
ENG-FORM: 806-0112.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
3.3.4 Resetting the Protective Circuit
The PA700 Series amplifier is designed with self protecting circuitry to interrupt the operation whenever
unusual conditions exist which might damage the amplifier components.
Unusual conditions might be excessive voltage, voltage spike, speaker short or temperature rise. Once
the protective circuit is activated, the flow of power is stopped in the affected channel and no further
operation is possible without corrective action. If the trouble was due to a temporary or transitory cause,
operation may be resumed by simply selecting the power switch to OFF and back to ON. If the protective
circuit again shuts the amplifier off, continued operation on that channel is probably impossible without
correcting the problem.
During a mission, should one channel fail, the amplifier can be operated by using the unaffected channel.
The available audio power will be approximately half the normal power. It is advisable to remove the
power cable from the affected channel.
CAUTION:
The transistors of this system are subject to damage when exposed to excessive heat, voltage,
or current for even short periods of time.
The PA700 Series incorporates a protective circuit, which disables the amplifier when safe
operating currents or voltages are exceeded. The protective circuit is adequate in most
instances however, it is also subject to damage when the unit is exposed to extreme or
sustained stresses. Careful monitoring is therefore necessary when operating under unusual
environmental extremes. Precautions should be taken to maintain temperature within
recommended limits. Other damaging conditions are excessive battery charging voltages, short
circuits within the system and transmission of compressed high level music resulting in
continuous high-level power generation.
Operation at high temperature should be limited to short periods. Even at normal temperatures,
operation at continuous full power should be interrupted for 5–10 seconds at 15 second
intervals.
Loudspeakers will overheat with a continuous signal at full power. Voice operation will generate
less heat, and pauses between words will result in a low duty cycle.
Section 3 ends