User manual ACR ELECTRONICS EM-2BA MEGAPHONE

[. . . ] 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. [. . . ] 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. Replace microphone and mouthpiece assembly (2). Align keyway and secure with the three set screws (3). 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 a clicking sound is heard, the speaker is operating. 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. 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. 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. 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. Remove the three oval head screws (10) at periphery of the speaker end of the housing (14). Extract Speaker & Megaphone Subassembly by firstly turning horn (15) clockwise approximately 45°. [. . . ] CAUTION: Observe polarity of batteries during installation procedure (see instructions at battery tube openings of the megaphone). 7 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. [. . . ]