Honeywell KMA28 Mounting Rack Installation, Connector Assembly, Cable Harness Wiring, Noise

Bendix/King

KMA28

Audio Amplifier/Intercom/Marker Beacon Receiver

2.3.3 Mounting Rack Installation

Set the unit aside in a safe location until needed. Install the tray using six FHP 6-32 x ½" screws. The audio selector panel must be supported at front and rear of the mounting tray.

2.3.4 Connector Assembly

The unit connectors mate directly with the circuit boards in the KMA 28. The connectors are a Molex crimp-type, and require the use of a Molex hand crimp tool, EDP P/N 11-01- 0203, CR6115B (or equiv.). The connectors are mounted to the unit tray with #4-40 screws, from the inside of the tray. Ensure that proper strain relief and chafing precau- tions are made during wiring and installation.

2.4Cable Harness Wiring

Referring to the appropriate Appendix, assemble a wiring harness as required for the in- stallation. All wires must be MIL-SPEC in accordance with current regulations. Two- and three-conductor shielded wire must be used where indicated, and be MIL-C-27500 or equivalent specification. Proper stripping, shielding and soldering technique must be used at all times. It is imperative that correct wire be used.

Refer to FAA Advisory Circular 43.13-2A for more information. Failure to use correct techniques may result in improper operation, electrical noise or unit failure. Damage caused by improper installation will void the warranty.

2.4.1 Noise

Due to the variety and the high power of radio equipment often found in today's general aviation aircraft, there is a potential for both radiated and conducted noise interference.

The KMA 28 power supply is specifically designed to reduce conducted electrical noise on the aircraft power bus by at least 50dB. Although this is a large amount of attenuation, it may not eliminate all noise, particularly if the amplitude of noise is very high. There must be at least 13.8 VDC present at the bottom connector, pin 20, of the KMA 28 for the power supply to work in its designed regulation. Otherwise, it cannot adequately attenuate power line noise. Shielding can reduce or prevent radiated noise (i.e., beacon, electric gy- ros, switching power supplies, etc.) However, installation combinations can occur where interference is possible. The KMA 28 was designed in a RFI hardened chassis and has internal Electromagnetic Interference (EMI) filters on all inputs and outputs.

Ground loop noise occurs when there are two or more ground paths for the same signal (i.e., airframe and ground return wire). Large cyclic loads such as strobes, inverters, etc., can inject noise signals onto the airframe that are detected by the audio system. Follow the wiring diagram very carefully to help ensure a minimum of ground loop potential. Use only Mil Spec shielded wires (MIL-C-275000, or better).

Radiated signals can be a factor when low level microphone signals are "bundled" with current carrying power wires. Keep these cables physically separated. It is very important

006-10565-0000 Page 2-2 Rev. 0, Sept. 2000