PRODUCT
SUPPORT
FAA PMA Approved under A3-06-1405
EM-2BA™
MANUAL
Y1-03-0057
(25-60-06)
Overhaul Manual
with Illustrated Parts List
Rev. F
Product No. 2206
Portable Safety Megaphone
ACR Electronics, Inc.
5757 Ravenswood Road
Fort Lauderdale, Fl 33312
+1(954) 981-3333 • Fax +1 (954) 983-5087
www.acrelectronics.com
Email: Info@acrelectronics.com
A Chelton Group company
TABLE OF CONTENTS
SECTION TITLE PAGE
1.0 Description 1
2.0 Technical Data 1
3.0 Operation 2
4.0 Cleaning 4
5.0 Battery Replacement 4
6.0 Testing 4
7.0 Trouble Shooting 5
8.0 Disassembly 6
9.0 Inspection Check 6
10.0 Repair 6
11.0 Assembly 7
12.0 Parts List 9
ILLUSTRATION
Figure 1 Block Diagram 3
ACR/EM-2BA Portable Safety Megaphone
Figure 2 Illustrated Parts List 8
ACR/EM-2BA Portable Safety Megaphone
i
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Y1-03-0057 Rev. F
1.0 DESCRIPTION
1.1 The ACR/EM-2BA is a battery operated solid state megaphone
specifically developed for use in enclosed areas such as in the interior of
an aircraft or ship cabin. It has been designed to minimize regenerative
acoustic feedback that results in whistling and other oscillations of this
nature. It has a 90° sound projection angle to direct the sound to persons
in its immediate vicinity, as well as in the rear sections of any aircraft.
The amplifier frequency band-pass has been selected to produce a crisp,
clear reproduction of voice signals. The operating power level is also
sufficient to provide adequate sound under high ambient noise level
conditions without being over-powering. Specific attention has been
given to the physical size so that it can be used effectively in a crowded
environment.
1.2 The integrated circuit amplifier only uses a small current when turned
“ON”. Large currents necessary to drive the speaker are utilized only on
voice peaks. This extends the life of the batteries so that several hours of
operation may be expected when used normally in an intermittent manner.
Batteries should be replaced periodically as recommended by the
manufacturer. (See section 5.0) A simplified block diagram of the
megaphone is shown in Figure 1.
1.3 A battery test circuit is included. A flashing green LED indicates that the
battery is Ok.
2.0 TECHNICAL DATA
Dimensions 5.5” max diameter bell, 11.5” max long
Weight 2.3 lbs., including batteries
Materials Horn, handle – Anodized Aluminum
Housing – Aluminum
Attachment Neck strap at top of unit
Gain Control* Thumb operated
Amplifier Integrated circuit, 3 watts power output
Speaker Re-entrant horn and driver type;
input power five (5) watts;
90° dispersion angle
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Y1-03-0057 Rev. F
Batteries Six (6) standard 1½ volt “AA” cells
Power Drain 25 milliamps static current
550 milliamps maximum current
Frequency Response 500 to 3500 Hz
Battery Test Circuits Visual Flashing Green LED
3.0 OPERATION
3.1 To test the battery, squeeze the handle and note if the green LED (located
near the volume control cap) is flashing. The batteries are useable as long
as the LED flashes.
3.2 Hold the megaphone in one hand. Place mouth almost in contact with the
microphone mouthpiece at the rear of the assembly. Squeeze the handle,
which will flex slightly, turning the megaphone “ON” and speak slowly
with loud, crisp, clear tones.
3.4 Adjust the volume control knob to a suitable sound level. The volume
control may be adjusted with the thumb of the same hand holding the
megaphone.
3.5 When not in use, carry the megaphone by the neck strap, attached to top of
unit.
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Y1-03-0057 Rev. F
SPEAKER
ASSEMBLY
AUDIO AMPLIFIER
SIREN CIRCUIT &
BATTERY MONITOR
MEGAPHONE
SUB-ASSEMBLY
-
++
FIGURE 1
BLOCK DIAGRAM
ACR/EM-2BA PORTABLE SAFETY MEGAPHONE
4.0 CLEANING
4.1 External surfaces of the megaphone may be cleaned with a soft cloth,
dampened in a solution of mild household detergent. Do not immerse in
water or use strong solvents. Clean electrical contacts with cloth
dampened with isopropyl alcohol.
5.0 BATTERY REPLACEMENT (see Figure 2)
5.1 The power supply used in the megaphone consists of six standard 1 ½ volt
“AA” size batteries. Current drain is minimal (25 mA) with the
megaphone “ON”, and increases when the user speaks into the
microphone.
VOLUME
CONTROL
N.O.
N.C.
HANDLE
SWITCH
MICROPHONE
ASSEMBLY
-
+-
BATTERY
PACK
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Y1-03-0057 Rev. F
5.2 Battery replacement is accomplished by removing three set screws (3)
while holding the microphone and mouthpiece assembly (2) in place. The
six battery cells, contained in three tubes with two cells per tube, are
immediately accessible and will drop out when the megaphone is tilted.
New batteries may be dropped into the tubes, observing polarity marking
adjacent to each tube.
5.3 Replace microphone and mouthpiece assembly (2). Align keyway and
secure with the three set screws (3).
CAUTION: Observe polarity of cells carefully before replacement.
6.0 TESTING
Note: The megaphone consists of three major assemblies; the microphone and
mouthpiece assembly, the megaphone sub-assembly, and the horn and
speaker assembly. To locate a defect, follow the procedure outlined
below:
6.1 Squeeze the handle. If a clicking sound is heard, the speaker is operating.
6.2 If no sound is heard, remove the microphone and mouthpiece assembly
and the batteries. Check that both the microphone and battery contacts are
clean. If not, clean with a mild, non-abrasive cleaner such as alcohol.
6.3 Test amplifier and speaker assembly by replacing the microphone with a
spare microphone assembly. If no sound can be produced after
microphone replacement, it may be assumed that the amplifier or speaker
assembly is defective.
6.4 To test the speaker, disassemble the speaker. Disconnect one wire and
apply 1 ½ volts intermittently across the speaker. If no clicks are heard,
the speaker is defective.
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Y1-03-0057 Rev. F
7.0 TROUBLESHOOTING
7.1 Testing procedure for locating defects is given in paragraph 6.0. Possible
faults and corrections are summarized below for ready reference.
TROUBLE POSSIBLE CAUSE CORRECTION
No sound from speaker
when handle is squeezed
(Step 6.1)
Exhausted batteries,
defective microphone,
speaker or amplifier
Replace defective
component
assembly
Sound is abnormally low or
distorted
Exhausted batteries or
wrong polarity of battery
series
Check proper insertion of
batteries or replace
batteries.
Speaker does not respond to
Defective speaker Replace speaker
Step 6.4
8.0 DISASSEMBLY (see Figure 2)
8.1 Megaphone should be disassembled for repair or replacement of
components only.
8.1.1 Remove microphone and mouthpiece assembly (2) by removing
the three set screws (3).
8.1.2 Remove battery cells (4) from the three tubes by tilting megaphone
to allow cells to drop out into the hand.
8.1.3 Remove the three oval head screws (10) at periphery of the speaker
end of the housing (14).
8.1.4 Extract Speaker & Megaphone Subassembly by firstly turning
horn (15) clockwise approximately 45°. Secondly pull the entire
assembly gently until it stops. Rotate the assembly
counterclockwise 45°, then pull the entire assembly out.
8.1.5 The Speaker Assembly (6) and Megaphone Subassembly (9) can
be separated by firstly unplugging the speaker wires from the "out"
header and then removing the hex screw that holds the asesmbly
together.
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Y1-03-0057 Rev. F
8.1.6 Disassembly in steps 8.1.1 through 8.1.5 above is sufficient to
examine the megaphone for faults and testing. Further
disassembly is not recommended.
9.0 INSPECTION / CHECK
9.1 Inspect unit for any evidence of damaged parts, loose mountings or broken
leads and dirty electrical contacts.
10.0 REPAIR
10.1 The megaphone consists of three major sub-assemblies; the Microphone
and Mouthpiece Assembly, the Megaphone Sub-Assembly, and the Horn
and Speaker Assembly. Repairs are restricted to the replacement of these
defective sub-assemblies or the batteries and lanyard assemblies.
11.0 ASSEMBLY
11.1 Assembly of the megaphone is in reverse order of disassembly. Follow
these instructions:
11.1.1 Align Horn (15) and Speaker Assy (6) with location pins on
Megaphone Subassembly (9)
11.1.2 Attach Horn (15) and Speaker Assy (6) to Megaphone
Subassembly (9). Route Speaker wires through provided slot.
11.1.3 Plug Speaker connector into the "out" header.
11.1.4 Push entire assembly gently into the Housing (14) until it stops.
Turn clockwise 45° and push all the way in. Turn
counterclockwise 45° and align holes.
11.1.5 Replace screws (10)
11.1.6 Replace the six batteries (4) in three tubes at microphone end of
megaphone case.
CAUTION: Observe polarity of batteries during installation
procedure (see instructions at battery tube openings of the
megaphone).
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Y1-03-0057 Rev. F
11.1.7 Replace microphone and mouthpiece assembly (2). Align keyway,
and secure with the three setscrews (3).
11.1.8 Steps 11.1.1 through 11.1.7 complete the assembly of the
megaphone. After assembly, test unit in accordance with
Paragraph 6.0, Testing.
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Y1-03-0057 Rev. F
FIGURE 2
ACR / EM-2BA PORTABLE SAFETY MEGAPHONE
ILLUSTRATED PARTS LIST
8
12.0 PARTS LIST
12.1 Replaceable parts are illustrated in Figure 2, and listed below in the table.
Part numbers shown in the “Part Number” column may be ordered from
ACR unless another manufacturer’s name is given in parenthesis in the
“Description” column., In this case, replacement parts can be obtained
directly from the original manufacturer. Standard parts (MS-, AN-, etc.)
and commercially available hardware (‘Commercial’) should be obtained
from commercial sources.
ITEM QTY NOMENCLATURE ORDER SPARE PARTS
EM-2BA EM-2BA
♦
1 1
2 1 Microphone & Mouthpiece Assy 9211 9211
3 3 Socket Setscrew Kit 9416 9416
4 6 Battery AA Alkaline Commercial Commercial
5 1 Hole Plug A1-05-0562 A41-05-0562
6 1 Speaker Assembly 9419
7 3 Screw Self tap (#4 x ¾) Commercial N/A
8 2 Wire leads (#26AWG) Commercial N/A
9 1 Megaphone Subassy 9419
10 3 Screw Machine (#4-40 x 3/8) Commercial Commercial
11 1 Handle Kit 9423 9423
12 & 13 1 Strap assembly Kit 9233 9233
14 1 Housing, Megaphone A1-18-1151 A1-18-1151
15 1 Horn, Megaphone A1-17-0809 A1-17-0809
Megaphone, Safety Obsolete #2206
S/N < 2000
(Upgrade Kit)
(Upgrade Kit)
S/N ≥ 2000
9418
9421
♦
♦
S/N ≥ 2000 are date coded 4/99 +
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