PS Engineering PM500EX Installation Manual - Manual (Page 3)

April 2011 Page 3 200-118-0100
3. Depending on the panel thickness (< 0.040”) you
may elect to use a locally fabricated aluminum
faceplate to provide additional support. Place the
aluminum plate over the knob shafts, and secure
with the #4-40 screws provided.
4. Next install the two knobs by pressing them on
the shafts.
5. Remove the backing from either the vertical or
horizontal face label, carefully align over the
knob shafts, and press on firmly.
6. To complete the installation, a wiring harness
must be made and routed as shown at the back of
the manual.
IMPORTANT: You must use separate shielded
cable for the microphone and headphone jacks. Com-
bining these two wires WILL cause loud feedback and
degrade the intercom functions. The cause of the feed-
back is due to the fact that there is a much larger signal
being carried by the headphone wire than the micro-
phone wire. When these two wires are within the same
shielded cable, cross-coupling allows the output to get
back into the input, causing oscillations to occur.
If the aircraft already has pilot and copilot headset
jacks installed, you may re-use the hardware. Remove
all wires from the copilot jacks and discard them.
NOTE: You may elect to use the existing pilot headset
jacks as the auxiliary jacks.
To hook the intercom into the system, simply par-
allel a set of mic and headphone wires from this set of
auxiliary jacks directly to appropriate points to the
PM500EX. Finally, install a new set of pilot headset
jacks and hook directly to the appropriate points to the
PM500EX.
Electrical Noise Issues
Due to the variety of radio equipment found in
today's general aviation aircraft, there is the potential
for both radiated and conducted noise interference.
The PM500EX has a power supply designed to reduce
conducted electrical noise on the power bus by over 50
dB. Although this is a large amount of attenuation, it
may not eliminate all noise when the amount of noise
is excessive. In addition, there must be at least 13.8
Volts DC present at the PM500EX for the power sup-
ply to work in its designed regulation. Otherwise, it
will not be able to adequately attenuate all noise.
Shielding can prevent radiated noise (i.e. beacon,
electric gyros, switching power supplies) however,
installation combinations can occur wherein minor
interference is possible. The PM500EX was designed
in a RFI hardened chassis and has internal bypass ca-
pacitors on all input lines. RFI can still cause prob-
lems, like low or distorted sidetone, if correct shielding
techniques are not observed.
Ground loop noise occurs when there are two
ground paths for the same signal, i.e. airframe and
ground return wire. Large cyclic loads such as strobes,
inverters, etc., can inject audible signals. Follow the
wiring diagram very carefully to help prevent
ground loop potential. Radiated signals are also a fac-
tor when low level mic signals are "bundled" with cur-
rent carrying power wires. Keep these cables separated
as much as possible.
Mil-spec 2– and 3-conductor shielded wire MUST
be used as shown in the installation diagram for
proper operation. Use of other types could void the
warranty.
It is crucial that you use insulating washers on all
microphone and headphone jacks to isolate the audio
signal ground from the aircraft ground.
Power Requirements
The PM500EX is designed to work with either 12
or 28 volt DC negative ground systems. The
PM500EX must be externally fused with a 1 ampere
circuit breaker.
Side Tone
If the aircraft radio does not have sidetone (the
ability to hear your voice during radio transmissions)
the PM500EX can be modified to provide sidetone for
you. Call the factory for details.
Entertainment Hook Up
A low cost entertainment device (CD player, cas-
sette player, etc.) can be connected to the PM500EX.
You may want to install a ⅛" connector (not provided)
somewhere in the panel so that you can easily connect
an entertainment device.
The entertainment will be automatically muted
when the ICS becomes active. The “Soft Mute™” fea-
ture slowly returns the music to full volume when the
NOTE: A custom wire harness can be custom made to
your specifications by the factory. Call the factory for
more details.
NOTE: Do not remove the nuts from the volume
and squelch controls.
NOTE: Auxiliary microphone and headset jacks
are required for a complete installation. These pro-
vide troubleshooting and a back-up
access to the aircraft radios.
Note: Use the low level (or line) output from any music de-
vice to connect to the PM500EX. Maximum input level is 2 V
peak-to-peak.
DO NOT USE SPEAKER OUTPUT.
These levels will cause internal damage.