Northern Airborne Technology PA110 - Manual (Page 7)

PA110/220 High Power Audio Amplifiers
SM35 Installation and Operation Manual
Section 2 Rev: 1.00 Issue 4 Page 2-2
ENG-FORM: 805-0117.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
2.4.2 Cautions
CAUTION:
Use shielded cable exactly as shown and ground as indicated. All audio
installations can be severely degraded by incorrect wiring and shielding.
Unusual buzzes, hums or other background audio are symptomatic of multiple
grounds, or noisy external systems such as blowers or pumps sharing wiring
with the audio system. Never operate any of the PA amps below their rated
impedance of 10
Ω, except as indicated for the PA110.
2.4.3 Cabling and Wiring
All wire shall be selected in accordance with the original aircraft manufacturer's Maintenance Instructions
or AC43.13-1B Change 1, Paragraphs 11-76 through 11-78. Unshielded wire types shall qualify 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 connector map in
Section 2.6 as required.
Allow 3" from the end of the shielded wiring to the shield termination to allow the connector hood to be
easily installed. Reference the interconnect drawing in Section 2.6 for shield termination details. Note that
the hood is a "clamshell" hood, and is installed after the wiring is complete. Aircraft harnessing shall
permit the unit to be removed from the panel for easy access.
Maintain wire segregation and route wiring in accordance with the original aircraft manufacturers
Maintenance Instructions.
Unless otherwise noted, all wiring shall be a minimum of 22 AWG, except power and ground lines, which
shall be a minimum of 16 AWG, and speaker wires which should be at least 18 AWG. Reference the
Interconnect drawing for additional specifications. Check 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. Power to this unit must be supplied from a separate circuit breaker
or fuse (fast blow), and not attached to any other circuit breaker without additional protection. Verify that
the selected circuit breaker size and wire gauge are adequate for the installation using the techniques
specified in AC43.13-1B Change 1, Paragraphs 11-47 through 11-51 and 11-66 through 11-69.
2.4.4 External Switches
If the PA110 is driven directly from an AA90 controller via an amplifier, or if for any reason an AA21/22 is
not used, then a remote power switch (to disable the PA amp) may be desired.
2.4.5 Post Installation Checks
2.4.5.1 Voltage/resistance checks
Do not attach the power amplifier until the following conditions are met.
PA110
Check the following:
a) P101 pins <6>, <18> and <19> for +28 Vdc relative to ground.
b) P101 pins <4>, <5> and <17> for continuity to ground (below 0.5
Ω).
c) Speaker connections are correct for the speaker impedance, and are not shorted.