Telex Airman 850 Aviation Headsets Manual

Telex Airman 850 Aviation Headsets Manual
Airman 850 Headset
Maintenance and Overhaul Manual for the Airman 850 Headset
F.01U.264.819
Rev. 05
JUNE/2018
2
Airman 850
Record of Revisions
Rev No.
Revision Date
Change Description
A
03/2004
Created
2
02/2012
This document was completely reformatted and version letter was
changed to a version number
3
05/2012
Page 24
4
11/2017
Never released
5
06/2018
Updated entire document and validated content
Airman 850
3
Purpose of Manual
This manual, Bosch part number F.01U.264.819, contains information for the overhaul and servicing of the Airman 850 headset.
Technical Support
A liaison between the customer and factory is provided by the Bosch Product Support Department. Consultation and assistance on technical
problems, part information, and availability of local and factory repair facilities is available. When writing, include all information
concerning problem and mail to:
Bosch Communications, Inc.
8601 Cornhusker Hwy
Lincoln, NE 68507 U.S.A.

Attn: Aircraft Product Support Mgr.
Telephone: 877.863.4168
Parts Ordering
Replacement parts may be ordered from our parts department. When ordering, please include the following information:
•
Model Number
•
Part Description
•
Part Number
•
Quantity
Mail To:
Bosch Communications, Inc.
8601 Cornhusker Hwy
Lincoln, NE 68507 U.S.A.

Attn: Parts Department
Telephone: 800.553.5992
Fax: 402.467.3279
E-mail: [email protected]
Repairs
In order to maintain the FAA certification, all repairs to the headset must be made only by persons authorized under Part 43 of the Federal
Aviation Agency regulations. Bosch offers full support and repair.
4
Airman 850
Table
of
Contents
CHAPTER 1 
Description and Specifications .................................................................................................................
1.0 Description and Specifications.................................................................................................
1.1 General Description ...........................................................................................................
1.2 Models Covered .................................................................................................................
1.3 Specifications .....................................................................................................................
CHAPTER 2 
Disassembly/Assembly.............................................................................................................................
2.0 Disassembly/Assembly ..........................................................................................................
2.1 Disassembly .....................................................................................................................
2.1.1 Remove Cushions (Item 3)......................................................................................
2.1.2 Remove Faceplate Assembly (Item 4) ....................................................................
2.1.3 Remove Sleeve (Item 8)..........................................................................................
2.1.4 Remove Boom Assembly/Cover (Item 13).............................................................
2.1.5 Removing the Circuit Board (Item 9 or 10) ............................................................
2.1.6 Removing the Housing (Item 6 or 7) or Temple Plate 
Assembly (Item 15 and 16) from the Headband Assembly (Item 1)......................
2.1.7 Removing the Glider Assemblies (Item 2) and Glider Springs (Item 18) ..............
2.2 Assembly..........................................................................................................................
CHAPTER 3 
Parts List ..................................................................................................................................................
3.0 Parts List.................................................................................................................................
3.1 General .............................................................................................................................
3.2 Airman 850, Catalog Number 301317-000, -002, -003, -101, -200, 
-201, -300, and -400.........................................................................................................
CHAPTER 4 
Wiring Diagrams .....................................................................................................................................
4.0 Wiring Diagrams ....................................................................................................................
4.1 Airman 850 Wiring Diagram (Catalog Numbers 301317-000, -002, 
-003, -101, and -400) .......................................................................................................
4.2 Airman 850 Wiring Diagram (Catalog Numbers 301317-200, -201, and -300)..............
4.3 Connector Views/Wiring Diagrams .................................................................................
4.3.1 Connector View for Catalog Numbers 301317-000, -003, -200, 
-300, and -400 .........................................................................................................
7
7
7
7
8
11
11
11
11
11
12
12
12
12
12
13
17
17
17
18
21
21
21
23
24
24
6
Airman 850
4.3.2 Connector View for Catalog Numbers 301317-101 and -201 ................................. 24
4.3.3 Connector View for Catalog Numbers 301317-002 ................................................ 24
4.3.4 Connector Wiring Diagram for Catalog Numbers 301317-000, -003, -101,
-200, -201, -300, and -400 ...................................................................................... 25
4.3.5 Connector Wiring Diagram for Catalog Number 301317-002 (5-Pin XLR)........... 25
CHAPTER 5 
Maintenance............................................................................................................................................. 27
5.0 Maintenance............................................................................................................................ 27
5.1 Microphone Validation and Adjustment........................................................................... 27
5.1.1 Microphone/Amplifier Sensitivity Check................................................................ 27
5.1.2 Microphone Sensitivity Adjustment ........................................................................ 28
5.1.3 Troubleshooting Mic Failure ................................................................................... 29
5.2 Speaker Validation and Adjustment ................................................................................. 31
5.2.1 Speaker Sensitivity and Frequency Response Verification ..................................... 31
5.3 ANR Validation and Adjustment...................................................................................... 32
5.3.1 Active Noise Reduction (ANR Versions Only)....................................................... 32
5.3.2 Minimum Attenuation Requirements (Linearize between points) .......................... 32
5.3.3 ANR Test Procedure ................................................................................................ 32
5.4 Cleaning the Unit .............................................................................................................. 34
CHAPTER 6 
Troubleshooting ....................................................................................................................................... 35
6.0 Troubleshooting Chart ............................................................................................................ 35
CHAPTER 1
Description and Specifications
1.0 Description and Specifications
1.1
General Description
The Telex Airman 850 is a lightweight aviation headset complete with a boom-mounted, noise-canceling
electret microphone.
Lightweight design with soft, pliable cushions, adjustable headband, extended frequency drivers, and a noise
canceling electret microphone result in a comfortable headset providing the ultimate in clear, understandable
communications.
The Airman 850 headset with boom microphone is approved for aircraft use under FAA TSO’s C57a and
C58a.
1.2
Models Covered
This manual only covers models listed here. Not all of the models listed here are currently active and may not
be available in the market. Bosch can, at its discretion, discontinue models and part numbers.
Model
Number
Description
ANR
Connector and Wiring Used
301317-000
Airman 850 Headset, Dual-sided
Yes
PJ-068 (or equivalent) & PJ-055 (or equivalent)
Figure 10 on page 25
301317-002
Airman 850 Headset, Dual-sided
Yes
XLR Figure 11 on page 25
301317-003
Airman 850 Headset, Dual-sided
Yes
PJ-068 (or equivalent) & PJ-055 (or equivalent)
Figure 10 on page 25
301317-101
Airman 850 Headset, Dual-sided,
customer specific
No
PJ-068 & PJ-055 Figure 10 on page 25
301317-200
Airman 850 Headset, Single-sided
No
PJ-068 (or equivalent) & PJ-055 (or equivalent)
Figure 10 on page 25
301317-201
Airman 850 Headset, Single-sided,
customer specific
No
PJ-068 & PJ-055 Figure 10 on page 25
301317-300
Airman 850 Headset, Single-sided
Yes
PJ-068 (or equivalent) & PJ-055 (or equivalent)
Figure 10 on page 25
301317-400
Airman 850 Headset, Dual-sided,
customer specific
Yes
PJ-068 (or equivalent) & PJ-055 (or equivalent)
Figure 10 on page 25
8 Description and Specifications
1.3
Airman 850
Specifications
Receivers:
Type: Dynamic
Impedance: See Table 2 on page 9.
CAUTION: Damage could occur to avionics equipment if used with headset versions which are not
manufactured for use with 600 Ohm headsets. If in doubt, consult the avionics
equipment manufacturer.
Frequency Response: See Table 1 on page 9.
Sensitivity: Volume selector in Low 90dB SPL ±5 dB at 1kHz, 1mW input to headset, at LOW
volume control setting.
Microphone:
Type: Noise-canceling amplified electret
Matching Impedance: 150 Ohms
Frequency Response: 300-6000Hz (RTCA DO-214 curve)
Sensitivity: -51 ±3 dB
(ref. 1V/[email protected], 12 VDC, 470 Ohm DC / 150 Ohm AC load)
Operating Voltage: 8-28 Vdc (470 Ohm load)
Active Noise Reduction:
All models with active noise reduction utilize the microphone system for power
Plug Type:
Varies by model, refer to parts list
Approximate Wearing Weight:
2.9 oz single-sided without cord
3.8 oz double-sided without cord
Approximate Gross Weight:
Single: 3.7 oz (105 g)
Double: 4.0 oz (113 g)
Cord Length:
Varies by model, refer to parts list
Color:
Black
User Controls:
Volume Hi/Low Switch, ANR on/off switch (varies by model)
Airman 850
Description and Specifications 9
TABLE 1. Receiver
Frequency Response (All Models)
Frequency
dB above/below 1K ref.
Reference Tolerance
350Hz
2
±6dB
400Hz
4
±6dB
500Hz
6
±6dB
600Hz
10
±6dB
700Hz
11
±6dB
800Hz
9
±6dB
900Hz
5
±6dB
1000Hz
0
±6dB
2000Hz
-13
±6dB
3000Hz
-15
±6dB
TABLE 2. Receiver
Model Number
Impedance by Model
Description
Receiver Impedance
301317-000
Airman 850 Headset, Dual-sided
150 Ohms
301317-002
Airman 850 Headset, Dual-sided
600 Ohms
301317-003
Airman 850 Headset, Dual-sided
600 Ohms
301317-101
Airman 850 Headset, Dual-sided, customer specific
150 Ohms
301317-200
Airman 850 Headset, Single-sided
150 Ohms
301317-201
Airman 850 Headset, Single-sided, customer specific
150 Ohms
301317-300
Airman 850 Headset, Single-sided
300 Ohms
301317-400
Airman 850 Headset, Dual-sided, customer specific
150 Ohms
10 Description and Specifications
Airman 850
CHAPTER 2
Disassembly/Assembly
2.0 Disassembly/Assembly
2.1
Disassembly
The following procedure allows for complete disassembly of the Airman 850 final assembly (see Figure 1 and
Figure 2).
IMPORTANT:
The removal process requires the steps to be followed in order. For example, to remove the boom
assembly, item 13, all steps before the Removing the Boom Assembly step must be completed and in
the listed order.
Assembly is the reversal of the disassembly procedure. Please take care when disassembling to note details
that may be required in the assembly process.
2.1.1
Remove Cushions (Item 3)
To remove the cushions, do the following:
1.
2.1.2
At any point on the ear cup, gently pull the cushion from the faceplate.
Remove Faceplate Assembly (Item 4)
To remove the faceplate assembly, do the following:
1.
2.
3.
At the same time, push the two (2) catches located in the faceplate out of the way (Figure 3).
Rotate the faceplate assembly approximately 10° counterclockwise.
Carefully, pull the faceplate assembly away from the housing (item 6 or 7).
NOTE: Do not pull more than 12mm away from housing at this time.
4.
Using a soldering iron, carefully disconnect the white and red wires from the speaker solder
terminals.
NOTE: Be careful not to touch plastic housing with soldering iron.
5.
Remove the faceplate assembly.
12 Disassembly/Assembly
2.1.3
Airman 850
Remove Sleeve (Item 8)
To remove the sleeve, do the following:
1.
Carefully slide a small tweezers or pick under the sleeve.
NOTE: Avoid touching or scratching the circuit board, item 9 or 10.
2.
Gently pry the sleeve up and away from the circuit board.
NOTE: If necessary, prying up the sleeve in several locations may be required to free the sleeve
from the housing (item 6 or 7), and the circuit board.
3.
2.1.4
Once freed, carefully remove the sleeve from the housing.
Remove Boom Assembly/Cover (Item 13)
To remove the boom assembly/cover, do the following:
1.
Insert a tweezers or small flat head screwdriver between the circuit board (item 9) and the
housing (item 6), gently pushing the cover away from the housing.
NOTE: It may be necessary to push around the housing in several locations to get the cover snaps to
free themselves from the housing.
2.
3.
4.
5.
6.
Carefully desolder the four (4) cord unit wires from the circuit board (boom side only).
Gently pry the circuit board away from the cover being careful not to break the boom wires
hidden on the other side.
Remove the cover foam (item11).
Once the board is free from the cover, desolder the three (3) boom wires from the circuit board
(boom side only)
Remove the circuit board.
NOTE: The board is still attached to the overhead wires (Dual Side Versions Only)
2.1.5
Removing the Circuit Board (Item 9 or 10)
Follow the steps in Remove Boom Assembly/Cover (Item 13).
>Disconnect the four overhead wires (Dual Side Versions Only)
2.1.6
Removing the Housing (Item 6 or 7) or Temple Plate Assembly (Item 15 and 16)
from the Headband Assembly (Item 1)
>Push the housing off the glider assembly (item 2) through the slot in the top of the housing.
NOTE: Care should be taken to not bend the headband assembly or housing during this process, as it
may take some force to do.
2.1.7
Removing the Glider Assemblies (Item 2) and Glider Springs (Item 18)
1.
2.
Bend the upper metal portion of the glider assembly straight.
Gently pull the glider assembly out of the headband assembly (item1).
NOTE: The glider spring is located under the glider assembly and may spring out if the glider
assembly is removed too quickly.
3.
Repeat steps 1 and 2 for other side of the headset.
Airman 850
2.2
Disassembly/Assembly 13
Assembly
IMPORTANT:
Assembly is a reversal of the disassembly procedure. Steps need to be done exactly the reverse order of
the disassembly procedure to ensure proper headset fit and operation. Please take care to properly align
parts and wires to ensure proper operation. See disassembly procedure, parts lists, assembly diagrams,
and wiring diagrams for reference.
FIGURE 1.
Airman 850 Headset, Dual Sided, Exploded View
14 Disassembly/Assembly
Airman 850
FIGURE 2.
Airman 850 Headset, Single Sided, Exploded View
Airman 850
Disassembly/Assembly 15
Catch
(Push from other
side of faceplate
Catch
(Push from other
side of faceplate
Assemble
e
tat
Ro
Remove
FIGURE 3.
10°
Faceplate Disassembly/Assembly View
16 Disassembly/Assembly
Airman 850
CHAPTER 3
Parts List
3.0 Parts List
3.1
General
When replacing parts, consult Figure 1 on page 13, Figure 2 on page 14, and the parts list.
Choose the parts corresponding to the catalog/model number on the Headband Assembly
(Figure 1 on page 13, item 1).
18 Parts List
3.2
Airman 850 Customer Maintenance Manual
Airman 850, Catalog Number 301317-000, -002, -003, -101, -200, -201, -300, and -400
MODEL
Item CTN Numbers
1
2
a
3
4
SAP Numbers
Description
64318095
F01U152147
HEADBAND ASSEMBLY
64318107
F01U152148
HEADBAND ASSEMBLY
64318117
F01U152149
HEADBAND ASSEMBLY
No longer available
HEADBAND ASSEMBLY
S-F01U329356
HEADBAND ASSEMBLY
F01U329356
000 002 003 101 200 201 300 400
1
1
1
1
1
No longer available
HEADBAND ASSEMBLY
S-F01U329357
F01U329357
HEADBAND ASSEMBLY
S-64318118
F01U216802
HEADBAND ASSEMBLY
800801000
F01U153681
GLIDER ASSEMBLY
2
2
2
2
2
2
2
2
591486000
F01U151390
CUSHION,EAR, ROUND
1 piece
2
2
2
2
1
1
1
2
800456020
F01U118432
EARCUSHION (2 per pkg.)
1
1
1
1
1
1
1
1
800939000
F01U153698
FACEPLATE/SPEAKER ASSY
2
2
2
2
1
1
1
1
70413002
F01U152604
1
1
702171000
F01U152574
70413011
F01U152609
1
1
5
No longer available
CORD
Approximate Length: 
5.5 ft. (1.7 m)
CORD
Approximate Length: 
6.5 ft. (2 m)
CORD
Approximate Length:
5.5 ft. (1.7 m)
CORD
Approximate Length: 
6.3 ft. (1.9 m)
1
1
1
1
1
1
1
1
1
6
701613000
F01U110130
HOUSING,BOOM SIDE
1
1
1
1
7
701612000
F01U110129
HOUSING NON BOOM
1
1
1
1
S-701614000
F01U259442
SLEEVE 1 piece
2
2
2
2
1
1
1
2
S-701614000
F01U329353
b
SLEEVE 10 piece
1
1
1
1
1
1
1
1
S-F01U344779
F01U344779
PCB BOOM SIDE
1
600704100
F01U157606
PCB BOOM SIDE
S-F01U344780
F01U344780
PCB ASSY 600
S-F01U344776
F01U344776
PCB ASSY 600, reduced X-talk
S-F01U344775
F01U344775
PCB ASSY 300
S-F01U344777
F01U344777
8
9
10
No longer available
11
591385000
F01U151370
PCBAAIRMAN 850 - NON
BOOM SIDE
PCBAAIRMAN 850 - NON
BOOM SIDE
COVERFOAM
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
1
1
1
2
Airman 850 Customer Maintenance Manual
Parts List 19
MODEL
Item CTN Numbers
12
SAP Numbers
Description
000 002 003 101 200 201 300 400
701610000
F01U152470
COVER,NON-BOOM SIDE
1
1
1
800789000
F01U153679
BOOM ASSEMBLY
1
1
1
800789100
F01U153680
BOOM ASSEMBLY
74169A
F01U153213
800456019
F01U110451
15
70531101
F01U152640
16
70533000
17
18
13
14a
19c
20
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
TEMPLE PAD NOT PRINTED
1
1
1
F01U110213
FOAM PAD
1
1
1
590637000
F01U157438
CLOTHINGCLIP
1
1
1
1
1
1
1
1
64305000
F01U110016
GLIDER SPRING 1 piece
2
2
2
2
2
2
2
2
S-F01U327240
F01U327240
bGLIDER
1
1
1
1
1
1
1
1
57893000
F01U157434
ZIPPER POUCH
702126000
F01U152568
CARRYING CASE
1
1
1
1
1
RESISTOR, 300, 1/8W 5%
1
1
1
1
1
1
OVERHEAD CORDAGE
1
1
1
1
2
2
2
2
1
1
1
2
2
2
2
2
1
1
1
2
Not available from Bosch
WINDSCREEN
SPRING 10 piece
1
1
1
1
1
21c,d 53731000
F01U109567
22
54857101
F01U150106
23
54857103
F01U150110
24e
701246000
F01U152411
BOOM ROTATOR CAP
25f
701664000
F01U152484
ACOUSTIC CLOTH
2
2
2
2
1
1
1
2
26c,g S-F01U345383
F01U345383
ANR MICROPHONE
1
1
1
1
1
1
1
1
27c,h 35398005
F01U146873
5-PIN XLR CONNECTOR
a.
b.
c.
d.
e.
f.
WHITE WIRES FROM PCB TO
SPEAKER
RED WIRES FROM PCB TO
SPEAKER
1
Either part number is acceptable.
This item has 10 pieces. Only one or two springs are needed per unit.
Not shown.
This item is part of the headband assembly (#1) or can be purchased separately.
This item is part of Boom Assy (#13) or can be purchased separately.
Acoustic cloth is now included as part of #3. Only one acoustic cloth can be used at a time, either the
separate part that needs to be attached to the faceplate (#4) or the cloth that is included in the
replacement ear cushion
g. The ANR microphone is included with the PCBS and is sold separately.
h. This item is included in F01U152574 but is also sold separately.
20 Parts List
Airman 850 Customer Maintenance Manual
CHAPTER 4
Wiring Diagrams
4.0 Wiring Diagrams
4.1
FIGURE 4.
Airman 850 Wiring Diagram (Catalog Numbers 301317-000, -002, -003, -101, and 
-400)
Top Side, Airman 850 Headset, Dual-Sided Wiring Diagram
22 Wiring Diagrams
FIGURE 5.
Bottom side, Airman 850 Headset, Dual-Sided Wiring Diagram
Airman 850
Airman 850
4.2
Wiring Diagrams 23
Airman 850 Wiring Diagram (Catalog Numbers 301317-200, -201, and -300)
FIGURE 6.
Airman 850 Headset, Single-Sided Wiring Diagram
24 Wiring Diagrams
4.3
Airman 850
Connector Views/Wiring Diagrams
4.3.1
Connector View for Catalog Numbers 301317-000, -003, -200, -300, and -400
FIGURE 7.
4.3.2
Connector View for Catalog Numbers 301317-101 and -201
FIGURE 8.
4.3.3
Airman 850 Headset, Connector View (Molded Plugs)
Airman 850 Headset, Connector View (Mechanical Plugs)
Connector View for Catalog Numbers 301317-002
FIGURE 9.
Airman 850 Headset, Connector View ( XLR Plug)
Airman 850
Wiring Diagrams 25
4.3.4 Connector Wiring Diagram for Catalog Numbers 301317-000, -003, -101,
-200, -201, -300, and -400
PJ-068
(or equivalent)
PJ-055
(or equivalent)
FIGURE 10.
Airman 850 Headset, Connector Wiring Diagram
4.3.5 Connector Wiring Diagram for Catalog Number 301317-002 (5-Pin XLR)
Pin 5 N/C
Pin 1 White
5 1
43 2
Pin 4 Black (shield)
Pin 2 Yellow
Pin 3 Red
FIGURE 11.
Airman 850 Headset, 5-pin XLR Wiring Diagram
26 Wiring Diagrams
Airman 850
CHAPTER 5
Maintenance
5.0
Maintenance
5.1
Microphone Validation and Adjustment
5.1.1
Microphone/Amplifier Sensitivity Check
Headphone specifications are designed to comply with FAA TSO C57a, 
RCTA DO-214 & DO-160D.
The headphone has two (2) operations (ANR version only): 
(1) Passive- power is turned off. 
(2) Active - power is turned on. Passive versions operate in passive mode only. 

All modes tested, unless noted otherwise.
To test the sensitivity of the microphone, do the following:
1. Construct a test circuit. For more information, see Figure 12.
2. Connect the test circuit to the microphone plug of the headset. For more
information, see “Connector Views/Wiring Diagrams” on page 24.
NOTE:
Verify correct polarity of connections.
FIGURE 12.
Airman 850 Headset Boom Microphone Sensitivity Check and Adjustment Test Circuit
28 Maintenance
Airman 850
3. Calibrate a lab microphone.
4. Place the calibrated lab microphone 1/4 inch (6mm) above an artificial mouth
(Bruel and Kjaer type 4219).
5. Connect a signal generator to the artificial mouth.
6. Adjust for an output of 74dB SPL at 1kHz @ 1/4 inch from the opening to the
lab microphone.
7. Remove the lab microphone.
8. Position the headset microphone 1/4-inch (6mm) above the output of the
artificial mouth.
The acoustic hole in the boom mic should be aligned with the center of the
artificial mouth opening.
9. Measure the output of the headset microphone with a digital volt meter.
NOTE:
The output measured should be -51 ±3dBV.
5.1.1.1
Measure current of 12V Power Supply
The current should be 4mA ±1mA with sound pressure supplied to the mic
and ANR turned on.
The current should be less than 1mA without sound pressure supplied to
the mic and ANR turned off.
5.1.2
Microphone Sensitivity Adjustment
If the sensitivity of the microphone does not meet the requirements from section
5.1.1 on page 27, readjust the sensitivity.
To adjust microphone sensitivity, do the following:
>Turn the gain adjustment control in the microphone housing, using a small
screwdriver. For more information, see Figure 13.
>Clockwise adjustment increases output level.
Gain Adjustment
FIGURE 13.
Airman 850 Headset, Boom Microphone Gain Adjustment Location
Airman 850
Maintenance 29
5.1.3
Troubleshooting Mic Failure
The microphone circuitry is in two (2) parts; the boom microphone preamp and main
amp located on the main circuit board. If any failures occur in testing procedures
outlined in Sections 4.1 and 4.2, proceed to 4.3.1 and 4.3.2 to identify the failure.
5.1.3.1
Testing the Boom Microphone Assembly
To test the boom mic assembly, do the following:
1. Construct a test circuit. For more information, see Figure 14.
2. Connect the red, green, and copper boom wires to the test circuit. For
more information, see Figure 15.
3. Position the boom microphone 6mm above an artificial sound source,
such as a Bruel and Kjaer type 4227.
4. Connect an audio frequency oscillator to the artificial sound source.
5. Adjust the artificial sound source for an output of 114dB SPL
(0dB=20mPa) at 1kHz.
6. With a voltmeter, measure the output of the boom microphone.
The output should be 134mVRMS ±50mV.
NOTE:
•
•
•
600
If the output does not fall within the tolerances, adjust the gain pot
as shown in Figure 13.
This test is not designed for absolute accuracy, but rather to tell if
the boom assembly is functioning properly.
If no output, or no acceptable output is obtainable, then replace the
boom assembly.
470
25uf
+
J2
25uf
25 Vdc
DEVICE UNDER
TEST
12 Vdc
220
V IN
V OUT
J3
FIGURE 14.
1/2W
J8
J9
Airman 850 Headset, Boom Assembly Test Circuit
30 Maintenance
Airman 850
RED
GREEN
COPPER
FIGURE 15.
5.1.3.2
IMPORTANT:
Airman 850 Headset, Boom Assembly Reference View
Testing the Circuit Board Assembly
This test is for testing the circuit board assembly 600704-100 only. No testing is
required for circuit board 800940-000.
To test the circuit board assembly, do the following:
1. Construct a test circuit. For more information, see Figure 16.
2. Connect the circuit board to the test circuit.
With Vin measuring 100mVRMS 1Khz, 
VOUT should read 210mVRMS ±60mV. 
If the output is outside this range, replace the circuit board.
600
470
25uf
+
J2
25uf
25 Vdc
DEVICE UNDER
TEST
12 Vdc
220
V IN
V OUT
J3
FIGURE 16.
1/2W
J8
J9
Airman 850 Headset, Circuit Board Test Diagram
Airman 850
5.2
Maintenance 31
Speaker Validation and Adjustment
5.2.1 Speaker Sensitivity and Frequency Response Verification
NOTE:
Headphone specifications are designed to comply with FAA TSO C57a, 
DO-214 & DO-160D. The headphone has two (2) operations (ANR version
only): 
(1) Passive- power is turned off. 
(2) Active - power is turned on. Passive versions operate in passive mode
only. 

All modes tested, unless noted otherwise.
Transducer Type:
Transducer
Impedance (at the
earphone plug):
Sensitivity:
Frequency
Response:
Dynamic
See Table 2, “Receiver Impedance by Model,” on
page 9, for impedance according to model.
(All Models) 90dB SPL ±5dB at 1kHz, 1mW
input to headset, at LOW volume control setting.
1mV based on input impedance of headset being
tested.
Must meet standards outlined in Table 1 on
page 9.
To measure the speaker, do the following:
1. Using a B&K type 4153 with 6cc coupler or equivalent, place the headset
speaker on an artificial ear, fitted with the appropriate coupler.
2. Supply the headset with a 1mW, 1KHz signal to appropriate connector. See
“Wiring Diagrams” on page 21 for connector wiring.
3. Measure acoustic output of headset using an audio analyzer.
Sensitivity should be 90dB SPL ±5dB re. 1mW at 1kHz, headset in low volume
setting.
32 Maintenance
Airman 850
4. Measure and record the acoustic output over the frequency range of 350Hz to
3KHz. 
The resultant curve should fit the limits as defined in Table 1 on page 9.
5. Repeat steps 1 through 4 with the second speaker, if applicable.
6. Measure current of 12V Power Supply.
The current should be 4mA ±1mA with 1mW applied to the speaker and ANR
turned on.
The current should be less than 1mA without 1mW applied to the speaker and
ANR turned off.
NOTE: If
the specifications are not met in either power on or power off mode,
printed circuit board failure should be suspected, see “Troubleshooting
Chart” on page 35.
5.3
ANR Validation and Adjustment
5.3.1
Active Noise Reduction (ANR Versions Only)
NOTE:
5.3.2
Minimum attenuation requirements are not requirements of FAA TSO.
Minimum Attenuation Requirements (Linearize between points)
Frequency (Hz)
Active (dB)
Min
200
-8.000
300
400
+2.000
-1.000
-10.000
600
5.3.3
Max
-2.000
-3.000
800
-12.000
-1.000
1000
-12.000
+0.000
ANR Test Procedure
5.3.3.1
Required Equipment
The Airman 850 ANR test and adjustment procedure requires the
following acoustic test equipment and custom fixture.
1. Audio Test System (for purposes of this procedure the
Audio Precision System 2 is referenced)
2. Artificial Mouth (Bruel & Kjaer 4227)
3. Artificial Ear with 6cc Coupler (Bruel & Kjaer 4153)
4. Supporting hardware for Microphone
5. Supporting hardware and software for audio test system
6. Custom ANR test and adjust fixture
Airman 850
Maintenance 33
5.3.3.2
Test Setup Block Diagram
FIGURE 17.
5.3.3.3
Custom ANR Fixture
FIGURE 18.
5.3.3.4
Test Setup Block Diagram
Custom ANR Test Fixture with Headset
Testing ANR
To test ANR, do the following:
1. Create a standard microphone test setup.
Output should be 1V, 400Hz, BP Pink Pseudo noise directly out to
artificial mouth mounted to test fixture. See Figure 18
•
Microphone amplifier filter should be set to A-weighing, if
available.
•
Frequency sweep should be set to 500Hz–1KHz Bandpass input
filter.
2. Adjust headset to minimum size.
3. Place headset on test fixture. For more information, see Figure 18.
4. Measure the headset.
•
•
With ANR turned off, perform a bandpass sweep, save this file.
34 Maintenance
Airman 850
With ANR turned on, perform a bandpass sweep, save this file.
5. Subtract the two sweep results (files), measured in step 3.
The resulting curve should fit within the limits as shown in “Minimum
Attenuation Requirements (Linearize between points)” on page 32.
•
5.3.3.5
Adjusting ANR
5.3.3.5.1 Set up acoustic test system
To set up the acoustic test system, do the following:
1. Create a standard microphone test setup.
Output should be 1V, 600Hz, sine wave directly out to artificial
mouth mounted to the test fixture.
•
Microphone amplifier filter should be set to A-weighting, if
available.
2. Adjust headset to minimum size and place on test fixture, as shown
in Figure 18.
5.3.3.5.2 Adjust the headset
•
To adjust the headset, do the following:
1. Place adjustment screwdriver through top of test fixture into back
ANR adjustment pot of the headset.
2. Monitor the microphone output on the acoustic test system.
3. Adjust ANR pot until the minimum output level is achieved, as
shown on the acoustic test system.
4. Perform the ANR test to confirm the headset meets the test
requirements.
5.4
Cleaning the Unit
IMPORTANT:
Use a mild detergent or isopropyl alcohol wipes to clean the plastic and
metal headset parts and ear cushions (not foam windscreen). Do not soak or
allow the cleaner to puddle on the unit and sit for long periods of time. The
cleaner should wipe off or evaporate quickly. Do not allow alcohol or any
liquid to touch the speaker or microphone element.

Cleaning directions here are considered for external surfaces only. Internal
surfaces should not require cleaning. The factory uses isopropyl alcohol to
clean parts before shipping, if needed.
CHAPTER 6
Troubleshooting
6.0 Troubleshooting Chart
Check
Plugs
Check
Main Cord
Receiver 
Inoperative
X
X
Microphone
Inoperative
X
X
Receiver
Intermittent
X
X
Microphone
Intermittent
X
X
Distorted Receiver
Signal
X
Distorted
Microphone
Signal
Check
Amplifier
Gain
Adjust
Check
Overhead
Corda
Check
Speakers
X
X
X
X
Check
Boom Mic
Assembly
X
X
X
X
X
X
X
X
Receiver Level
Varies Between
Left and Right
Sidesa
X
X
X
X
a. Only applies to dual-sided versions.
X
X
Receiver Level
Doesn’t Meet
Specifications for
Power On and
Power Off
Microphone Level
Cannot be
Adjusted Properly
Check
Circuit
Boards
X
X
X
X
36 Troubleshooting
Airman 850
APPENDIX A
ANR Fixture
38
Airman 850
39
Airman 850
1
2
3
4
5
6
7
8
9
10
11
A
THE ARTIFICIAL EAR IS
HELD IN PLACE BY THE
FRICTION FIT OF THE
O-RING
4.000in
101.60mm
ARTIFICIAL MOUTH
12
A
3.250in
82.55mm
6.250in
158.75mm
B
B
DETAIL D
SCALE 1 : 1
C
C
2.135in
54.23mm
3.500in
88.90mm
2.000in
50.80mm
C
.250in
6.35mm
D
D
2.380in
60.45mm
6.215in
157.86mm
C
E
D
1.405in
35.69mm
.433in
10.99mm
E
SECTION C-C
SCALE 1 : 2
F
distribution, as well as in the event of applications for industrial property rights.
Robert Bosch LLC [2008]. All rights reserved,
also regarding any disposal, exploitation, reproduction, editing,
F
ARTIFICIAL EAR
G
G
Ind.
YYYYMMDD
Change
Checked
Material
Lang.
en
ANR Test Fixture Drawing
2
3
4
5
6
7
8
Resp. dept.
Add info.
Size
H
From
Weight
Crit. P. Scale
1
Release BWN
Missed Details
MNR
FIGURE 19.
Drawn
Treatment
H
9
1:3
Sheet
1/1
AIRMAN 850 ANR TEST FIXTURE
Doc.Type
Mat. meets
DRW
Syst.
SW Repl. for
10
F01UXXXXXX
DP/TD Vers. Format
A2
Repl. by
11
12
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