Northern Airborne Technology AA23 - Manual (Page 14)

AA23 Speaker Amplifier Manual SM23 Rev. 4.00
2.3.3 Notes
The 600 Ω line input is a low level audio line, and connects to a sensitive point in the
AA23. This line must be shielded, and routed to avoid pick-up of stray fields in the
aircraft. The same holds true for the Headset and Mic inputs. Failure to do this will
result in noisy operation, and will easily pick up interference if poorly installed and
routed.
2.3.4
Cable and Wiring
All unshielded wire should be MIL-W-22759 or equivalent. 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 2.5 as required.
Allow 3 inches from the end of the wire to the shield termination to allow the hood to be
easily installed. Note that the hood is a “clamshell” hood, and is installed after the
wiring is complete.
All wiring should be 22 AWG, except power, output and ground connections, which
must be at least 20 AWG. Ensure that the ground connection is clean and well secured.
A 1 A fuse or breaker is recommended (28 VDC Source).
2.3.5 External
Components
When used as a multiple headset driver, some type of external series resistor is useful
to prevent shorted headsets or cables from shutting down the system.
2.3.6 Post-Installation
Checks
With the AA23 disconnected from its mating connector, carry out the following checks:
a) Check
pin <1> for +28 Vdc relative to ground, and pin <9> for continuity to
ground (below 0.5 Ω).
b)
Check for the correct load resistance on pin <7> or < 8>, to a return on pin <15>.
Do not power up unit if load resistance shows a short.
Do not attach the AA23 until these conditions are met, or damage may result to the unit
which is not covered under warranty.
Page 2-2 Nov 21,2003
ENG-FORM: 805-0105.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.