PS Engineering PMA8000BT NUI Installation Manual - Manual (Page 9)

PS Engineering
PMA8000BT Audio Selector Panel and Intercom System
Installation and Operator’s Manual for units with serial number CBT1561 and above
200-890-1702 Page 2-2 New, April 2011
32 x ½" screws (475-632-0012). The audio selector panel must be supported at front and rear of the mount-
ing tray.
2.3.4 Audio Panel Tray and Connector Assembly
The rack connectors mate with two 44-pin connectors in the PMA8000BT. The connectors are a sub-
miniature crimp-type, and require the use a hand crimp tool, from table below (or equiv.). The connectors
are mounted to the tray back plate with #4-40 screws (475-440-1038), from the inside of the tray and the
mounting block, 431-891-0100. Ensure that proper strain relief and chafing precautions are made during
wiring and installation, using the cable clamp (625-001-0002).
Two grounding lugs are provided, which may be attached to the rear mounting plate with 2 ea #4-40 x ¼”
screws with captivated lock washers. These provide a convenient location to connect the shield ground ter-
minations.
Manufacturer Crimping Tool Positioner Extraction tool
AMP 601966-1 601966-6 91067-1
Daniels AFM8 K42 M24308-1
ITT-Cannon 995-0001-584 995-0001-739 91067-1
Table 2-1 Connector Pin crimping tools
2.4 Cable Harness Wiring
Referring to the appropriate Appendix, assemble a wiring harness as required for the installation. 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 43.13-2B for more information. Failure to use correct techniques may re-
sult in improper operation, electrical noise or unit failure. Damage caused by improper installation will void
the PS Engineering warranty.
2.4.1 Electrical 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 PMA8000BT 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 connector,
J2 pins 8 & 9, of the PMA8000BT 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 gyros, switching power supplies, etc.) However, installation combinations can occur where interfer-
ence is possible. The PMA8000BT was designed in a RFI hardened chassis and has internal Electromag-
netic 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 air-
frame that are detected by the audio system. Follow the wiring diagram very carefully to help ensure a min-
imum of ground loop potential. Use only Mil Spec shielded wires (MIL-C-275000, or better). Under no
circumstances combine a microphone and headphone wiring into the same shielded bundle. Always use a 2-
or 3-conductor, shield wire as shown on the installation-wiring diagram.
The shields can be daisy-chained together, and then connected to the ground lugs mounted on the back plate
shown in Appendix B.
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 that you use insulated washers to
isolate the ground return path from the airframe to all headphone and microphone jacks.