AEM AA21-400 User manual

SPECIAL NOTICE
This product is now licensed to Anodyne Electronics Manufacturing (AEM) from Northern
Airborne Technology (NAT)/Cobham Aerospace Communications (CAC). AEM is responsible
for all matters related to this product, including sales, support and repair services.
Please note the transition to convert product manuals and supporting documentation is an
ongoing process and is being addressed on an ‘as needed’ basis.
All references to NAT product part numbers (and associated images) are equivalent to AEM
product part numbers.
Contact info:
Anodyne Electronics Manufacturing Corp.
#15-1925 Kirschner Road
Kelowna B.C. Canada
V1Y 4N7
Email: [email protected]
Toll Free: 1-888-763-1088
Phone: [phone]
Fax: [phone]
www.aem-corp.com
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CONFIDENTIAL AND PROPRIETARY TO ANODYNE ELECTRONICS MANUFACTURING CORP.
MAINTENANCE MANUAL
REV 5.00 November 9, 2016
Anodyne Electronics Manufacturing Corp.
15-1925 Kirschner Road
Kelowna, BC, Canada.
V1Y 4N7
Telephone [phone]
Facsimile [phone]
Website: www.aem-corp.com
© 2016 Anodyne Electronics Manufacturing Corp. (AEM),
All Rights Reserved
SM34
AA21
-400
Cabin PA System
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COPYRIGHT STATEMENT
© 2016 Anodyne Electronics Manufacturing Corp. (AEM), All Rights Reserved
This publication is the property of AEM and is protected by Canadian copyright laws.
No part of this document may be reproduced or transmitted in any form or by any means
including electronic, mechanical, photocopying, recording, or otherwise, without the prior
written permission of AEM.
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Prepared By:
Checked By:
Approved By:
The status of this Maintenance Manual is controlled by the revision shown on the title page. The status of
each section is controlled by revision shown in the footer of each page. All revisions affecting sections of
this manual have been incorporated.
AEM MANUAL REVISIONS
Revision Number
Revision Description
Date
Rev: 5.00
ECO1054: AEM Rebranding
Nov 9, 2016
Tony Pearson
Designer
Dec 7, 2016
Loen Clement
Designer
Dec 07, 2016
Tom Betzelt
Product Support Manager
Dec 7, 2016
Todd Blackstock
R&D Manager
Dec 9/16
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Table of Contents
Section Title Page
4.0 Theory
4.1 Introduction 4-1
4.2 Overview 4-1
4.2.1 Main Subassembly 4-1
4.2.2 Control Interface Subassembly 4-1
4.2.3 Backlighting Subassembly 4-1
4.3 Theory of Operation 4-2
4.3.1 Power Supply 4-2
4.3.2 Mic Input 4-2
4.3.3 Receive/CD Inputs 4-3
4.3.4 Sirens 4-3
4.3.5 Sidetone Output 4-4
4.3.6 Output Selection & Volume Control 4-4
4.3.7 External PA Output 4-5
4.3.8 Speaker Output 4-5
4.3.9 Temperature Sensor 4-5
4.3.10 +3dB Input 4-6
4.3.11 Backlighting 4-6
5.0 Maintenance
5.1 Introduction 5-1
5.2 Continued Airworthiness 5-1
5.3 Disassembly/Reassembly 5-1
5.3.1 Disassembly 5-1
5.3.2 Reassembly 5-2
5.4 Test Equipment 5-3
5.4.1 Test Cables 5-3
5.4.2 Test Jigs 5-3
5.5 Test and Alignment Procedures 5-3
6.0 Documentation and Drawings
6.1 Introduction 6-1
6.2 Documentation and Drawings 6-1
6.2.1 Product 6-1
6.2.2 Subassembly 6-1
7.0 Bulletins
7.1 Introduction 7-1
7.2 Bulletin Listing 7-1
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8.0 Supplements
8.1 Introduction 8-1
8.2 Supplement Listing 8-1
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Section 4.0 Theory
4.1 Introduction
Information in this section consists of a detailed discussion of the theory of operation, providing the
technician with the information necessary to perform in depth troubleshooting. See Section 6 for all
referenced drawings.
4.2 Overview
The AA21-400 Cabin PA control unit is designed to provide centralized control for an aircraft’s internal and
external PA systems in one panel-mounted unit with an illuminated faceplate. All audio and keylines are
interfaced to existing aircraft audio systems. Front panel switches provide selection of the various
operational modes of the AA21 and a potentiometer provides output volume control.
The AA21-400 design is composed of three subassemblies: the main subassembly, the control interface
subassembly and the backlighting subassembly.
4.2.1 Main Subassembly
The main subassembly contains circuits that include the power supply, input amplifiers, output amplifiers,
keyline input interfaces, siren audio generation, temperature monitor, and speaker output short circuit
protection. Components with 100- or 200-series numbers are located on this subassembly. Individual
functions of the main subassembly will be described in greater detail in the sections to follow.
4.2.2 Control Interface Subassembly
The control interface subassembly contains the unit’s main power switch, three mode selection switches,
main output volume control and a power status indicator. This subassembly interfaces to the main
subassembly with a 26-pin ribbon cable. Components with 400-series numbers are located on this
subassembly. The functions of this subassembly will be described in greater detail in the sections to follow.
4.2.3 Backlighting Subassembly
The backlighting subassembly provides the lighting components required to illuminate the text legends on
the front panel faceplate. This subassembly interfaces to the control interface subassembly with a two-pin
header connector. Components with 500-series numbers are located on this subassembly. The functions
of this subassembly will be described in greater detail in a following section.
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4.3 Theory of Operation
Refer to diagrams AA21-1A\401-0, AA21-4\401-0 and AA21-5\401-0
4.3.1 Power Supply
Positive 28 Vdc power is supplied to the AA21 through connector J101 pins 1 and 2, and power ground is
through connector J101 pins 14 and 15. Positive power is over-current protected by fuse F101. Power is
then noise filtered through T-network filter FL102 and choke L101. After filtering, the power is routed to
connector J102 pins 1, 2 and 25. Ribbon cable W1 transfers the power to connector J401 pins 1, 2 and 25.
Power is then switched on or off through front panel POWER switch S401. Power status indication is
provided by the circuit of resistor R402, LED DS401 and diode D401. LED DS401 illuminates green when
+28 Vdc power is applied to the AA21 and switch S401 is set to ON. Once switched on, the power is routed
to connector J401 pins 3, 4 and 26 and to connector J102 pins 3, 4 and 26 through ribbon cable W1. The
power is then reverse-voltage protected through diode D129 and over-voltage protected by zener diode
D130.
After D129/D130 the 28 Vdc power is fed in three general directions: output from the AA21, power to several
circuits on the main subassembly and power to further stages of the power supply. The 28 Vdc output is
over-current protected through fuse F102 and routed to connector J101 pin 8, labeled SWITCHED POWER.
The 28 Vdc power is directly supplied to three opto-isolators (U116, U118, and U119), three solid-state
relays (U103, U104, and U105) and the speaker output amplifier stage. Finally, the 28 Vdc power is supplied
to the remainder of the power supply described in the following paragraph.
Capacitors C158 through C161 provide filtering and charge retention for the 28 Vdc power. Resistor R205,
zener diodes D131, D132, capacitors C162, C163 and transistor Q106 form a circuit that provides series
pass regulation, and reduces the power to 22 Vdc for supply to the external speaker output amplifier. This
power is then regulated to 12 Vdc by the circuit containing U120 and D133, and routed to the siren generator
circuit, temperature sensor, and various amplifiers. The 12 Vdc is then fed into the 8 Vdc regulator circuit,
which includes U121 and D134, and the 8 Vdc output is used to provide mic bias and as a muting input to
the receive amplifier through U118. The 8 Vdc output is then fed into the input of the 5 Vdc regulator circuit,
which includes U124 and D135, to provide 5 Vdc output as a power input for mic amplifier U106, and as a
pull up for transistor Q103. Capacitors C164 through C168 and C177 provide noise filtering and charge
retention along the DC path of the power supply.
4.3.2 Mic Input
The mic signal is delivered to the AA21 from connector J101 pins 13 and 25. DC mic bias is supplied to pin
13, MIC HI, by a circuit comprised of R116, R117 and C103. The mic signal is then coupled through C102
and transformer T101. The mic is low pass filtered by R119, C106 and AC coupled to mic pre-amplifier
U106. The mic pre-amplifier has an integrated AGC control to ensure a consistent output level after the
maximum input level is exceeded. The mic pre-amplifier U106 levels off the mic input signal after 130
mVrms. The mic signal is then low-pass filtered by R121, C178.
This signal is then fed to two voltage-controlled amplifiers: the sidetone output driver U108 and the mic gain
amplifier U107. The sidetone amplifier gain is controlled by the S/T LEVEL trimpot R159. The gain of the
mic gain amplifier is controlled by the MIC LEVEL trimpot R126. The gain of the mic pre-amplifier is low-
temperature compensated by thermistor RT101 in series with the mic level trimpot, and thermistor RT102
in series with the sidetone level trimpot.
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After the mic gain amplifier, the mic signal is fed to solid state relay U103 where the signal may be selected
or de-selected. Depending on selection mode, the mic signal is either fed to external speaker driver U109
or to speaker driver U110 and U113. The sidetone amplifier U108 is enabled when an active low PA KEY
is applied to the AA21. To enable the mic gain amplifier, PA must be selected on the front panel of the
AA21, and an active low PA KEY must be applied to the AA21. The PA KEY signal causes a solid state
relay U118 to apply +8 Vdc to the cathodes of D119 and D120, thus reverse-biasing the diodes. This
activates the voltage-controlled inputs of mic amp U107 and sidetone amp U108 based on their respective
potentiometer level settings. When the PA is selected on the front panel, a ground is applied on PA/RX
switch S403 pins 1 and 4. These grounds are present on J401 pins 10 and 24 and are routed to J102 pins
10 and 24 by cable W1. When J401 pin 10 (PA) is active (grounded), it turns off Q103 and activates the
voltage control of the mic amplifier U107. When J401 pin 24 (RECEIVE DISABLE) is active (grounded), it
disables the receive amplifier and allows for mic signal only to be routed to the selected output stage.
4.3.3 Receive/CD Inputs
The receive/CD inputs only allow either receive or CD to be active at one time. This selection is achieved
by setting jumper JP105.
By installing a shorting block on pins 1 and 2 of JP105, the receive input is enabled. Receive audio high to
the AA21 is available on J101 pin 11, and low is on pin 23. The circuit containing components R161, C109
and R167 sets the input impedance and pass band for the receive audio input.
By installing a shorting block on pins 2 and 3 of JP105 the CD input is enabled. CD audio high input to the
AA21 is available on J101 pin 12 and low on pin 24. The circuit containing components R162, C110 and
R163 set the input impedance and pass band for the CD audio input.
The audio signal is then fed to a voltage controlled amplifier U114. The gain of this amplifier is controlled
by RECEIVE LEVEL trimpot R173. Capacitor C129 ensures smooth audio gain transitions when the receive
amplifier is enabled/disabled. The receive/CD output is enabled by selecting RADIO on the AA21 front
panel. This selection applies a ground to S403 pin 3, J401 pin 9 and J102 pin 9 (RADIO). The active
(grounded) RADIO turns off Q104 and allows the voltage controlled input of receive amplifier U114 to be
controlled by the RECEIVE LEVEL potentiometer setting. This same selection action removes the ground
from the PA control line and turns transistor Q103 on. When Q103 turns on, a ground is applied to the
voltage control of mic amplifier U107, thus disabling the mic amplifier when RADIO is selected. After the
receive amplifier, the audio signal is fed to the selected output.
4.3.4 Sirens
Siren mode selection is set using front panel switch S404 and has three settings: WAIL, OFF and YELP.
The wail and yelp sirens possess the same tone range but the yelp siren has a higher frequency sweep
rate than the wail siren. Both sirens are disabled when front panel switch S404 is set to the OFF position.
When the wail siren is selected, S404 pin 1, JP401 pins 1 and 2, and J401 pin 21 are all grounded. By the
same selection, the second pole of S404 applies a ground on S404 pin 4, JP402 pins 1, 2, and J401 pin
18. The ground at J401 pin 18 is routed to J102 pin 18 through cable W1. This ground enables sweep rate
adjustment through WAIL potentiometer R221. The wail siren also requires YELP/WAIL KEY to be active
(grounded) in order for the siren to be heard. This will be described later in this section.
When the yelp siren is selected, S404 pin 3, JP401 pins 5 and 6, and J401 pin 20 are all grounded. By the
same selection, the second pole of S404 applies a ground on S404 pin 6, JP402 pins 5 and 6, and J401
pin 19. The ground at J401 pin 18 is routed to J102 pin 19 through cable W1. This ground enables sweep
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rate adjustment through YELP potentiometer R222. The yelp siren also requires YELP/WAIL KEY to be
active (grounded) in order for the siren to be heard. This will be described later in this section.
The rate at which the siren tone sweeps is determined by the respective siren adjustment potentiometers
as well as the circuit associated with U123. The start and stop frequencies are determined by resistors
R217, R218, R219 and capacitor C174. The rate at which the siren tone sweeps between the start and stop
frequencies are determined by either R221 or R222. The ramp waveform output of U122 is present on pin
2 and is then attenuated by the resistor network of R213, R214, R215 and R216. The circuit centered
around U122 provides the sinusoidal tone output to the siren amplifier. The frequency of tone output from
U122 pin 2 is dependent on the swept ramp waveform provided by U123. The waveform symmetry of the
sinusoidal output is maintained by resistor R207. The output from U122 pin 2 is then attenuated by resistors
R208, R174 and R175. The siren audio is then AC coupled to siren amplifier U115 by capacitors C130 and
C131.
Either the WAIL ON or YELP ON from J401 pins 21 and 20 is grounded when WAIL or YELP is selected.
These signals are routed to J102 pins 21 and 20. The WAIL ON and YELP ON are combined on the main
subassembly. This signal named YELP/WAIL KEY is connected to U119 pin 6. When the SIREN KEY on
J101 pin 18 is activated (grounded) U119 is switched on and output pins 4 and 6 of the solid state relay are
connected. When grounds are present at SIREN KEY and YELP/WAIL KEY the base of transistor Q105 is
reverse biased thus turning Q105 off. This allows the voltage control (pin 4) of siren amplifier U115 to
amplify the siren audio at the level set by SIREN LEVEL potentiometer R179. A siren audio is only present
when the siren select switch on the front panel is set in WAIL or YELP mode, the SIREN KEY is active, and
the SIREN LEVEL potentiometer is set appropriately. The WAIL or YELP sweep rates are adjustable when
sirens are active by setting R221 or R222 respectively. Siren audio is routed only to the EXT PA output and
requires the front panel output selector switch S402 be set to EXT. Sirens will never be present on the INT
output (internal speaker). The siren audio is present for both settings PA or RADIO on front panel input
selection switch S403.
4.3.5 Sidetone Output
Sidetone audio is derived directly from the mic pre-amplifier output. The sidetone audio output is coupled
from the sidetone amplifier U108 to connector J101 by transformer T102. Sidetone audio output is a
differential output with the high side available on J101 pin 9 and the low side on J101 pin 21. The sidetone
output level is only adjustable by setting SIDETONE LEVEL potentiometer R159.
4.3.6 Output Selection & Volume Control
Selection of front panel switch S402 to INT applies a ground on S402 pin 3 and J401 pin 7. The internal
speaker selection signal is routed to J102 pin 7 and the cathode of D106. Diode D106 acts as protection
for U103 and U105 pin 4. The approximate ground level that is present on U103 pin 4 energizes the solid
state relay thus shorting pins 5 and 6 of U103 and opening pins 7 and 8. Resistor R113 provides current
limiting for the internal LED’s of U103. Now the mic or receive/CD audio present at pin 5 of U103 is switched
to pin 6 and 7 of U103 and connected to J102 pin 17 (POT HI). This audio signal is routed to J401 pin 17
and front panel VOLUME potentiometer pin 3. Volume potentiometer R401 attenuates the audio and
outputs this level adjusted output on pin 2. The audio on R401 pin 2 is connected to J401 pin 16 and routed
to J102 pin 16 (POT WIPER) through cable W1. The pot wiper signal is present at pin 5 of U104 through
pins 2 & 3 of JP101. This same signal is present at pin 5 of U105 through pins 2 & 3 of JP102. When INT
speaker is selected, the EXT speaker amplifier input is muted bya ground supplied by U104 pin 8 connected
to U104 pins 6 & 7. Solid state relay U105 is energized by an approximate ground at input pin 4, which
connects, pins 5 & 6 and opens pin 7 & 8. Resistor R115 provides current limiting for the internal LED’s of
U105. The audio present at U105 pin 5 is then connected to pins 6 & 7 and routed to the internal speaker
amplifier.
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