Northern Airborne Technology AA20-431 - Manual (Page 11)

AA20-431 Cabin PA System Manual SM22 Rev. 4.10
2.3.2 Warnings
Do not bundle any lines from this unit with transmitter coax lines. Do not bundle any
logic, audio, or DC power lines from this unit with 400 Hz synchro wiring or AC power
lines. Do not position this unit next to any device with a strong alternating magnetic field
such as an inverter, motor or blower, or significant audio interference will result.
2.3.3
Cautions
In all installations, use shielded cable exactly as shown, and ground as indicated.
Significant problems may result from not following these guidelines. All audio installations
can be seriously degraded by incorrect wiring and shielding, which may result in
abnormal cross-talk, hum and ground-loop noise. Particular care should be taken with all
microphone wiring, as these lines carry the lowest-level signals in the aircraft.
CAUTION:
Connecting speaker terminals to chassis ground
could cause damage to the unit.
2.3.4
Notes
a)
If the speaker load drops to less than 5 Ω the speaker output will toggle between
‘full’ and ‘no’ power. Returning the load to 8 Ω will return the AA20-431 to full power.
b) If the unit exceeds the high operating temperature limit, the output power will be
reduced by 50%.
2.3.5
Cable and Wiring
All unshielded wire shall be selected in accordance with AC43.13-1B Change 1,
Paragraphs 11-76 through 11-78. Wire types should be to MIL-W-22759 as specified in
AC43.13-1B Change 1, Paragraphs 11-85, 11-86, and listed in Table 11-11. For
shielded wire applications, use Tefzel MIL-C-27500 shielded wire with solder sleeves
(for shield terminations) to make the most compact and easily terminated interconnect.
Follow the wiring diagrams in Section 2.6 as required.
Allow 3 inches from the end of the wire to the shield termination to allow the connector
hood to be easily installed. Note that the hood is a ‘clamshell’ hood, and is installed
after the wiring is complete. Aircraft harnessing should permit the unit to be removed
from the panel for easy access to all adjustments. DO NOT mount the unit until all
adjustments have been carried out.
All wiring should be at least 22 AWG, except power, ground and speaker wires, which
should be at least 20 AWG. Ensure that the ground connection is clean and well
secured, and that it shares no path with any electrically noisy aircraft accessories such
as blowers, turn and bank instruments or similar loads.
Page 2-2 Apr 21, 2004
ENG-FORM: 805-0106.DOT
Amendment #2 Feb 17, 2009
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.