Repair Problem Solving Guide.PDF

David Clark Company Incorporated

360 Franklin Street, Box 15054

Worcester, MA 01615-0054

Phone: 508-751-5800 Fax: 508-753-5827

www.davidclark.com

___________________________________________________________________________________________________

Aviation headsets are functionally tested with a simple talk-listen check using a

compatible aviation intercom.

1. Insert headset plug(s) into intercom jack (s).

2. Don headset and speak into microphone. You should hear yourself (sidetone) in both

ears.

3. Cycle volume control(s) over full range while continuing to speak to ascertain proper

control operation.

4. If you are testing a stereo headset on a monaural intercom you will hear audio in only

the left (mic) side

unless the stereo - monaural switch in the comm cord yoke is in the monaural position.

5. If no audio is heard you can isolate the problem to the microphone or earphone side

of the headset by

plugging a second known-good headset into the test intercom. This will allow the

microphone and

earphone circuits to be cross tested.

6. The communication functions of ENC headsets are tested exactly as in steps 1

through 5 above. The active

noise attenuation function is independent of the communication signal paths.

7. To check for proper ENC operation provide operating power by way of batteries when

using an XL module

or a 12 to 28 volt source in the case of the XP module.

8. When the power is turned on you should hear a low level hiss in each ear. Room

noise should quiet

somewhat but may not be too noticeable unless there are significant low frequency

components in the noise.

Each side should be free of any oscillation or other undesirable sounds. If a problem is

common to both sides suspect a power supply or wiring problem.

Headset Problem Solving Guide

Problem

Possible Cause

Recommended Correction

Microphones

No Output

Defective Mic, Broken wire

Replace mic, cord or reconnect wire

Low Output

“ “

Replace mic

High Output

“ “

Replace mic

Mic Static

“ “

Replace mic

Intermittent Mic

Loose mic set screw or defective

Tighten mic set screws or replace mic

mic

Communication

cords

Intermittent at plugs

Dirty plugs or broken wire at

plugs

Clean plugs, see if problem is corrected, if not

replace comm cord

Intermittent at dome

Broken wire in cord at dome

Replace comm cord

No output from headset

Broken wire somewhere in cord

Replace comm cord

Intermittent at yoke

Broken wire at yoke

Replace comm cord

Mic cord Intermittent

mic cord

Broken wires at connector

Replace mic cord

Earphones

No output

Defective earphone, broken wire

Replace earphone, replace cord or reconnect

wire

Low output

“ “

Replace earphone

Earphone static

“ “

Replace earphone

Intermittent earphone

“ “

Replace earphone

Distorted output

“ “

Replace earphone

Volume control(s)

Intermittent volume

control

Defective volume control

Replace volume control

Only 1 earphone working

Broken wire

Resolder wire

Loose volume control

Loose nut

Tighten nut

Mic booms Broken flex

boom

Defective adhesive, customer

abuse

Replace boom

Broken wire boom

Defective boom

Replace boom

Headband spring

Broken headband spring

Defective headband spring

Replace headband spring

Each headset sent in for repair should have it’s plugs cleaned, domes buffed or cleaned as best

as they can be, old ear seals, filters and any head pad that is worn out replaced.

Trouble Shooting Chart

Standard Noise Cancelling

Headsets

Begin: Buff plugs and put in mono mode. Plug

headset into an aviation intercom and speak into mic..

Can you hear both earphones?

Can you hear from one earphone?

Measure volume control(s) with meter on

green & black contacts of the audio plug. If

they don't change the readings

accordingly, then they are bad. Note: In

stereo, measure resistance from tip to

sleeve & ring to sleeve. In mono measure

tip to sleeve.

YES

Any shorts between plugs on comm cord? **

Yes

First make sure that it isn't in stereo

mode, then replace earphone from

silent side. Is it ok now? Note:

Stereo headset plugged into mono

intercom will only have sound in left

ear unless yoke switch is moved to

mono position.

Find colors of shorted

lines & pinpoint from

inside comm cord dome.

Yes

Take another good headset & put

it's mic. plug into the DC Comm

instead. Speak into the second

while listening to the first. Can you

hear yourself?

Rotate volume controls with meter

on tip (green) & sleeve (black)

contacts of audio plug. Any

response?

Put good mic into headset.

Do you hear now?

Yes

Check readings between mic screws

(or female mic cord plug) & mic

comm plug for shorts or opens.

Open left dome & check between

mic plug & bad line & dome to mic

cord

Disconnect black & green

wires just inside dome.

Check for open in comm

cord, broken wires before

or at splits in dome, or two

shorted earphones.

Do "wiggle" test on cords

for all headsets

Yes

If left side, check all readings

between green wire split. If right

side, disconnect one wire from

earphone & check wires at both

ends of overhead cord, & wires

between ear & overhead.

Make sure that you're not in

stereo mode. Is that it?

Yes

Then earphone is shorted on

good volume side.

BC 12-12

**For stereo headset troubleshooting, using mono intercom, in mono mode the ring (yellow) wire is open &

the tip (green) splits off into both earphones. In "S" mode, ring is switched closed to right ear. The left ear

(green) is completed & the black ground is connected to both ears.

Trouble Shooting Chart

Electronic Noise Cancelling

Headsets

Begin: Buff plugs, install good batteries & put in

mono mode. Put headset into an aviation intercom &

speak into mic.. Can you hear both earphones?

Test volume controls in both stereo & mono mode.

Test OK?

Can you hear from one earphone?

Turn on power module. Does

it cancel noise in both ears?

If volume controls do not affect

circuit they are defective.

Test each ear

module one at a

time, with volume

controls. If either

one does not cancel

equally or efficiently,

replace that module.

Flip Switch on cord

to Stereo mode.

Does this bypass

one ear module?

(A loud squeal

signifies improper

wiring at module.)

Did it cancel in one ear?

Replace the

ear module

that did not

cancel.

Cancel now?

Did it sound like the

ANR went on?

Follow the orange

& brown wires

from where they

enter the dome to

the ear module

that did not

cancel until the

open is found.

Both ear

modules are

defective

Measure voltage at

orange & brown wires

as they exit the power

module towards the

dome. Does it read

9 or 12 volts?

Do wiggle

test to check

cords for all

headsets

Look for short at plugs &

trace those shorted

colors up through wires

by stopping at each

solder juncture to

disconnect one.

Look for open in

wires starting at the

brown & orange

coming out of the

power module & up

to where they enter

the dome.

In power module check

switch operation & its

wires, check wires to &

from battery contacts,

test L.E.D., & then if all

else fails, troubleshoot

the PC Board.

YES NO

YES

YES NO

Rotate volume control

on silent side while

measuring at the

sleeve & tip (black &

green) of the audio

plug. Works OK?

Any shorts at plugs? **

To find short in

headset follow known

shorted colors by

disconnecting one of

them at each junction

point until pinpointed.

Use 2nd good

headset to see if

you can hear that

mic. Can you hear

now?

Problem is in the mic

line. Use the regular

aviation trouble-

shooting flowchart to

test.

Turn on the ANR.

Can you hear

now?

Out of both

earphones?

Did you hear the ANR turn

on at all?

Both ear

modules

are bad.

Replace the one

you heard.

Troubleshoot the

rest of the

headset as though

it were a normal

aviation headset

with no output in

one ear.

Replace one

ear module.

Can you

hear that

side?

Replace

both ear

modules. If

that does

not solve the

problem

there is

probably

more than

one open.

Start from

plugs &

continue up

into domes.

Check for open in

the green/volume/

ear/black line in that

dome (or overhead

if applicable)

Troubleshoot as

though it were a

regular aviation

headset with no

output at ears.

Defective ear

module.

Both ears

were bad for

different

reasons.

Rotate vol.

Controls while

measuring at

green & black

contacts of audio

plug. Do both

affect circuit?

NOYES

YES

YES NO

YES

** Note: The dual plugs on ANR headsets are wired the same as stereo.

Also be aware that feedback from a bad com mic. can make the ear modules

sound "tinny" or less efficient. Replace before swapping ear modules.

BC 12-5-12