User manual ACR ELECTRONICS EM-2BA MEGAPHONE

[. . . ] 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. [. . . ] When not in use, carry the megaphone by the neck strap, attached to top of unit. 3. 2 3. 4 3. 5 3 Y1-03-0057 Rev. F SPEAKER ASSEMBLY AUDIO AMPLIFIER SIREN CIRCUIT & BATTERY MONITOR MEGAPHONE SUB-ASSEMBLY VOLUME CONTROL MICROPHONE ASSEMBLY - + + N. O. N. C. HANDLE SWITCH + BATTERY PACK - 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. 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. 4 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. CAUTION: Observe polarity of cells carefully before replacement. 5. 3 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 6. 2 Squeeze the handle. If no sound is heard, remove the microphone and mouthpiece assembly and the batteries. 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. Disconnect one wire and apply 1 ½ volts intermittently across the speaker. If no clicks are heard, the speaker is defective. 6. 3 6. 4 5 Y1-03-0057 Rev. F 7. 0 7. 1 TROUBLESHOOTING Testing procedure for locating defects is given in paragraph 6. 0. Possible faults and corrections are summarized below for ready reference. TROUBLE No sound from speaker when handle is squeezed (Step 6. 1) POSSIBLE CAUSE Exhausted batteries, defective microphone, speaker or amplifier assembly Exhausted batteries or wrong polarity of battery series Defective speaker CORRECTION Replace defective component Sound is abnormally low or distorted Check proper insertion of batteries or replace batteries. Replace speaker Speaker does not respond to 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). Remove battery cells (4) from the three tubes by tilting megaphone to allow cells to drop out into the hand. [. . . ] 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. 8 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. [. . . ]