PS Engineering PMA7000CD Installation Manual - Manual (Page 12)

PS Engineering
PMA7000CD- Series Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-790-0010 Page 2-4 Revision 10, September 2005
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.
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.
Adding a high-performance audio control system, particularly in conjunction with high-performance active
noise canceling headsets, cannot improve on older avionics that were designed for cabin-speaker use. PS
Engineering makes no claim that the audio panel will provide a noise-free audio quality under all installa-
tion conditions, particularly with older avionics.
2.5.2 Existing KMA-24 Installation
If the installation replaces a KMA-24 (series -01, -02 or -03), the existing 44 pin connector can be used for
the bottom connector of the PMA7000CD tray as is, providing it is properly installed and wired. No other
changes are required except for external marker lights (see Section 3.7.2 for details). The "key" in the ex-
isting connector must be located between pins 7 and 8. This connector will be used in the bottom connector
position. (See Appendix for complete wiring harness details.)
The existing ground bus may be reused for radio shield connections, if it was constructed so it can be relo-
cated to the PMA7000CD tray.
2.5.3 Existing PMA6000 installations
In 28-Volt aircraft, the dropping resistor may be removed, however, the 2 Amp breaker should be changed
to 3 Amp. If the old unit is stereo (PMA6000S or PMA6000MS), no rewiring is necessary except to add
additional features.
2.5.3.1 Stereo PMA7000CD installations into monaural PMA6000, PMA6000M.
Installations replacing PMA6000 or PMA6000M require re-wiring of the top connector to accommodate
the stereo configuration. See appendixes for detailed interconnect information.
2.5.4 Power
The PMA7000CD-Series are compatible with both 14 and 28 Volt DC systems. A two (2) Amp circuit
breaker is required for 14 VDC installations, and a three (3) Amp breaker for 28 VDC aircraft. Power and
ground wires must be a twisted #18 AWG pair. Connect airframe power ground to J1 (bottom connector)
Pin Z only. No dropping resistors are required.
2.5.5 Communications Push-to-Talk
An important part of the installation is the PTT (Push-To-Talk) switches that allow the use of your aircraft
communications radio for transmissions. There are three typical configurations that can be used. Select the
case that best fits the installation. Only the person who presses their PTT switch will be heard over the ra-
dio. If the pilot and copilot both use the PTT, the only pilot position has access to the radio. The pilot posi-
tion will have PTT control regardless of the mic selector switch or copilot PTT when the PMA7000CD is
in the
OFF /E MG mode.
CASE I: PTT is built into both pilot and copilot yokes.
CASE II: PTT is in pilot yoke only. This configuration requires a modified external PTT switch plugged
into the copilot's microphone jack. (See Appendix A). When the copilot's PTT is pressed, the intercom
switches the microphone audio from pilot to copilot mic.
CASE III: No built in PTT. This requires two built in PTTs to be installed, or modified external PTT
switches to be used. Modify external PTT as required. See Appendix A.