PS Engineering
Audio System Installations
Theory and Practices
Disclaimer
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Your PS Engineering Dealer is responsible for the product installation.
– Refer specific interface questions and procure any special tools or additional
installation supplies from the PS Engineering retail dealer.
– All PS Engineering dealers have an FAA Certified Repair Station with at least a
Limited Radio Rating, and are qualified to make these installations.
If the installation is not performed by a PS Engineering dealer or a custom wire
harness is not purchased, the warranty is VOID.
Installation of an intercom in a certified aircraft in accordance with
regulations may require specific knowledge, experience and tools.
– FAR 65.81 (b) A certificated mechanic may not exercise the privileges of his
certificate and rating unless he understands the current instructions of the
manufacturer, and the maintenance manuals, for the specific operation
concerned.
This presentation does not contain basic information about crimping,
soldering, or fundamental assembly techniques. These skills are required
to fabricate a wiring harness.
Either the PS Engineering authorized dealer or PS Engineering can make a
custom harness for you for products made by PS Engineering.
Why can’t we help with installation
questions?
• We don’t have the expertise. We have never
performed an installation, so we must rely on
avionics shops that have the knowledge and
tools to perform installs.
• We don’t have the necessary resources to
provide the technical support necessary to aid in
installations.
• To assure proper installation, we have trained our
dealers about the specifics about our products.
This assures that we will not have warranty costs
associated with improperly installed products
Applicability
• This presentation applies to:
– Intercom Installation
– The intercom portion of audio panel
installation
• This does not apply to:
– Radio Interface to Audio Panels
– Any other avionics installation
– Any wiring practice not specifically addressed
Topics
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Overview
Tools and Hardware Required
Theory of shielding and overall harnesses
The interface for the intercom
Building the Harness for the intercom
How to properly make shield terminations
The Intercom Installation
How to ground the harnesses
Entertainment interface
Troubleshooting
Overview
• Build Harness for Installation
• Create Wire Harness per the Wiring Diagram located in
the Installation Manual
• Route cables to the mounted mic and headphone jacks
throughout aircraft
• Route cables to the music and telephone inputs as
necessary
• Connect audio panel/intercom to power and ground
• Verify power and ground continuity
• Mechanically Install Audio Panel/Intercom in panel
– Note: If installing Intercom, Install Auxiliary Microphone and
Headphone Jacks
• These are the jacks that will connect directly to either the
single radio or to the audio panel.
• Test these jacks using a headset and in-line PTT switch
to assure you can hear and transmit over the radio
Tools and Hardware Required
Tools
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Wire Strippers (Ideal Strip Master)
Wire Cutters
Crimping Tool (Palatine PA1440)
Soldering Station (WTCPT)
Drill
Philips Screwdriver #1
Molex
Crimping tool
(PMA6000/70
00 Series)
Use “A”
Strip 18-24
AWG
Crimping tool for
PMA8000/9000series (High Density)
Hardware
Jacks
• Three types
– Microphone, Headphone (mono and stereo)
• Mono Phones (1/4”)
– 2 Conductor
• Stereo Phones (1/4”)
– 3 Conductor
• Microphone (mic) jacks –
Note, the mic jack has a smaller opening than the headphone jacks
– 3 conductor
– Smaller inside diameter
Wire
• All wire must be aircraft grade
– Tefzel insulation for flammability requirements
– Single conductor must meet MIL-STD 22759
– Multiple Conductor must be shielded, and
meet MIL-STD 27500
– Microphone and stereo headphones must be 3conductor with shield.
– Mono headphone must be 2-conductor with
shield
– Never use the shield to carry signals or
grounds
Wire Marking
• Identification markings should be placed
at each end of the wire and at 15-inch
maximum intervals along the length of the
wire.
• Wires less than 3 inches long need not be
identified.
• Wires 3 to 7 inches in length should be
identified approximately at the center.
Raychem Solder Sleeves
– Heat evenly until the
blue and white rings
melt, and provide a
plug on each end.
avoid overheating the
wire.
– Watch the wire/braid
connection to see the
solder fully wetting the
connection.
Theory of shielding and overall harnesses
Shielding
• Shield grounded at one end keeps RF out
because undesired currents can’t flow.
• Braided shields grounded at one end
create a Faraday RF shield.
• Stray signals seek a low impedance (Z)
path to ground. The properly terminated
braid shield provides that path.
Schematic Representation
Typical Audio Installation
Unit Connector
3-conductor w/shield
1
2
3
Mic Audio Low
Mic Audio Hi
Mic Key
4
5
Phones Audio Low
6
Phones Audio Hi
2-conductor with shield
Shield Termination
Floating Shields
PS Engineering Wiring Schematic
Unit Connector
3-conductor w/shield
2
3
6
Mic Audio Low
Mic Audio Hi
Mic Key
Phones Audio Hi
2-conductor with shield
Shield Termination
Notice how in the top
schematic the low is
connected to a unit pin. In
some PS Engineering
installations, to save space,
the low side is connected to
the shield ground AT THE
UNIT.
This is NOT the same as
using the shield as the audio
low.
Phones Audio Low
5
This shows some typical
shielding schematics.
Floating Shields
The number of solid wires
that pass trough the
ungrounded end of the shield
signifies the number of
conductors in the cable.
The Aircraft RFI/EMI Jungle
• Countless sources of RFI/EMI Energy
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Comm radios
Electric motors (flaps, trim, blower)
Switches
Alternators & generators
Strobes & beacons
Other audio systems
• Any and all will create noise in the audio
system
– Unless you follow manufacturer’s installation
instructions
Audio Low
• Return path for audio signals
– Older avionics may not have a dedicated audio
low – use chassis ground at radio/audio panel
• Never use a shield as current carrying wire.
All shields must remain un-terminated at the
jack end.
• Never use airframe ground as audio return
path
Ground Do and Ground Don’t
• DO ground shields at one end ONLY
• DO tie shields together at ONE (1) end
– Almost always the signal SOURCE
• Don’t ground the jacks mechanically
• Don’t ground both ends of shield set
– even for different systems
• Don’t use the shield as an audio return
wire
• Don’t EVER run mic and headphone audio
in same shield (it will squeal!).
Single-point Grounding
• A designated ground on the unit or
system for connecting all shield and
circuit grounds.
• Designed to accept RFI and EMI and
pass safely around the signal paths.
• Any change in ground potential is
felt identically by all subsystems,
and ignored.
Block Diagram
COM radio or
Audio Panel
Aircraft Radio Headphone ,
Microphone, & PTT
PHONE MIC
PHONE MIC
PHONE MIC
AUX Jacks
Pass 2 Jacks
Pass 1 Jacks
PHONE MIC
PHONE MIC
Copilot Jacks
Pilot Jacks
Circuit Breaker
Music Jack
Power
Aircraft
Ground
11-33 VDC
For the Intercom installs, Auxiliary Jacks
• These are a REQUIRED part of any
intercom installation. It where the
Intercom is connected to the radio(s)
• Mechanical and Electrically interface
assures failsafe operation.
– Bypass intercom
– Use if intercom is removed
– Essential part of troubleshooting
AUX Jacks Schematic (for intercom installations)
To Aircraft Radio
Phone Hi
AUX Headphone Jack
To Aircraft Radio
Phone Low
Aircraft Radio PTT
Aux Mic Jack
To Aircraft Radio Mic Audio Lo
To Aircraft Radio
Mic Audio Hi
Building the Harness
• Strip outer jacket
• Comb out braid and fold back over jacket
• Create a drain wire for the shield:
– Using heat activated LC-3 Raychem sleeves,
insert a stripped “drain” wire between ring and
braid.
• Connect drain wire of the shielded cable to
appropriate ground point:
– If necessary, daisy-chain to other “drain”
wires, or connect to designated ground pin
Wire
Shield
Orange
Tracer
Blue
Tracer
White
PS Engineering Harness Conventions
Microphone
White – Ring – Mic Audio
Blue – Barrel – Mic Audio Low
Orange – Tip – Radio P-T-T
Headphone or Music
White – Tip – Audio (Rt)
Blue – Barrel – Audio Low
Orange – Tip – Audio (Lt)
Terminating Wire
Termination Complete
Solder melted and flowed
Seals melted
Heat Shrink conforms
Crimp
Strip 1/16” (depth of middle band)
Verify good crimp by pulling on the wire.
Insert and Close
Jack Wiring
• Mono Headphone
– Connect Audio Hi to tip
– Connect Audio Low to barrel
– Do NOT connect shield
Pilot Phones
• Stereo Headphone
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Connect Audio Right Hi to tip
Connect Audio Left Hi to ring
Connect Audio Low to barrel
Do NOT connect shield
Audio (Left)
Audio (Right)
Audio Low
Stereo
Headphone Jack
• Microphone
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Connect Push-to-Talk (Radio P-T-T) to tip
Connect mic audio to ring
Connect mic low to barrel
Connect low side of P-T-T to barrel
Do NOT connect shield
Pilot Mic Jack
Pilot PTT
Anatomy of a Jack
Tip
Mic Jack
Phones Jack
0.205” ID
0.250” ID
Ring
Stereo Jack or
Mic Jack Layout
Schematic View (3 conductor)
Tip
Ground
(Barrel)
Tip
Ring
Ground
(Barrel)
Ring
Shield
Jack/Plug Contacts
Barrel
Ring
Tip
Hardware Installation
• Connect pilot, copilot and passenger
jacks.
– Verify correct intercom operation, talk
between all seats and test all modes.
• Make connection between intercom
and existing (AUX) headphone and
microphone jacks connected to
radio/audio panel
Checkout Procedure
• With audio panel/intercom off, test FailSafe system by transmitting and receiving
on radio from Pilot Headset positon
• Turn intercom on
– Verify that the radio is not keyed
• Test radio receive and transmit on pilot
and copilot. Test intercom ISO and Crew
function (if present).
• Secure unit, harness and jacks.
Fail-Safe
• Connects pilot headphone and
microphone to radio through a relay
contact in closed position
• In fail safe when off, or power removed at
breaker.
• In stereo installation, radio audio will be in
one ear only
• Verify fail-safe on initial installation
– If it doesn’t work, the installation is wired
incorrectly
Intercom Installation
• Drill 6 holes
– 2 knobs
– Switch
– LED (if equipped)
– 2 mounting screws
PM1000II Template
Ø0.125
Ø0.25
Ø0.375
122-102-0001
Ø0.265
Jack Installation
• Drill 15/32” (0.450”) hole for each jack
• Place flat insulating washer on jack and
insert from rear.
• Place shoulder washer on jack so
shoulder fits into the hole.
• Add nut and tighten.
– Be sure that the jack barrel does not contact
the metal airframe.
– Be sure that no part of a headphone jack
touches a microphone jack
Sidetone
• Audio signal from COM radio of
transmission
– Designed to help person regulate voice
– In PS System it is passed through from the
COM
• Where did it go?
– Not present in some Cessna systems
• Separate sidetone output on some radios
– Can be lost through Radio Frequency
Interference (RFI) caused by improper
shielding
Entertainment Inputs
• One input on standard intercoms
• Two inputs on units with crew mode
– Second input active only in crew mode
• Requires a minimum audio level 1 V p-p
(Line Level) compatible with portable
devices
– Do NOT USE speaker levels from automotive
units
• Input jacks should not be grounded
– Install in plastic panel
Unswitched Inputs
• Only Available in PM3000, P/N
11931A
– Two inputs for alert audio, warnings etc.
• NO unswitched inputs on other
models
– Kluge installations are unapproved
– Some COM receivers have aux inputs
Installation
Troubleshooting
Symptom
Possible Cause
Excessive electrical Noise in intercom
Mic and or headphone jacks touching ground.
Incorrect shield connection
Intercom partially keys when turned on
Mic jack miswired
Failsafe doesn’t provide headphone audio
Stereo headphone jack miswired
No sidetone
Not provided on com phones output
Mic and or headphone jacks touching ground.
Incorrect shield connection
Audio squeal when volume on intercom turned
up
Mic and headphone signals crossed, or
running in same shield
Noise in system that goes away when radio or
intercom active
Music source introducing noise
Music jack is grounded
Intercom audio in one ear only
Stereo headset set to stereo in mono
installation