Northern Airborne Technology PA700 - Manual (Page 11)

PA700 Series High Power Voice Amplifier
SM44 Installation and Operation Manual
Section 2 Rev: 1.01 Issue 4 Page 2-2
ENG-FORM: 805-0117.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
2.4 Installation Procedures
2.4.1 Cautions
CAUTION:
Use of a fully floating audio wattmeter or transformer coupled meter is
recommended. Always check ADF and compass calibration after installing external
speakers or ‘PA’ amplifiers. Significant single cycle errors may be caused by the
concentration of steel and magnetic material.
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 this unit below its rated impedance.
When a remote control unit is used, all signal inputs must be made at that unit and a
cable of appropriate length will be necessary to connect it to the amplifier.
Precautions are necessary when external signals, such as intercom, radio or
recorders are used. The high gain of the amplifier requires care to prevent feedback
or crosstalk. Ground loops and stray currents in the input line must be eliminated.
2.4.2 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 2.7 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 2.7 for shield termination details.
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 20 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.