PS Engineering PMA9000EX Installation Manual - Manual (Page 9)

PS Engineering
PMA9000EX Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-920-0000 Page 2-2 Rev. 9, Jan. 2011
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
terminations.
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, shield-
ing 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 PS Engineering 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 PMA9000EX power supply is specifically designed to reduce conducted electrical noise on the air-
craft power bus by at least 50dB. Although this is a large amount of attenuation, it may not eli minate 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 PMA9000EX 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 interference is possible. The PMA9000EX was designed in a RFI hardened chassis and has inter-
nal Electromagnetic Interference (EMI) filters on all inputs and ou tputs.
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). 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 wash ers to
isolate the ground return path from the airframe to all headphone and microphone jacks.