PA Audio Amplifier

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General Information Operating Instructions Precautions Speaker Connections Catalog 
Precautions

General Installation Instructions, Information & Precautions

General instruction for all type of PA System. Check catalog / dealer in case of doubt.
Unpacking: The amplifier was thoroughly checked at the Factory. Take great care in unpacking your Amplifier. In case any damage is noticed, immediately take it to the Dealer from whom you purchased it, Do not discard the carton and other packing material as this may be useful for future transportation.
Installation: The Amplifier should be installed in dry well ventilated & cool place. Do not place anything on top or adjacent to the Amplifier which will restrict the airflow. The Amplifier should always be kept 10 to20cms. (6'') away from the back wall. Cooler the amplifier runs, longer shall be its life.
Grounding The Unit: The chassis of the amplifier must be grounded by connecting EARTH Terminal to a water pipe or with Earth outlet of AC mains, When cassette Player or Booster or any other equipment is connected, make sure that their chassis are also earthed with each other. Before connecting the amplifier to AC mains or battery operation make sure that  The required inputs such as microphones, cassette Recorder etc. are firmly connected to input jacks. The volume controls of the MIC/AUX. are turned to "O". The MIC switches are at OFF position (see explanation on MIC/Aux operation).  The group of loudspeakers are properly connected between COM and the matching output terminal. connections to be made only to one impedance at a time. Do not connect some speakers to 70V/100V line and some to 4ohms 8ohms. The Master control should be at "O" position. Bass & Treble controls are also at "O" (Flat) position.                             
220V-240V AC Operation: The Amplifier are provided with 220V & 240V taps, When leaving the factory it is connected to 240V tap. It is safe to operate with 240V taps because of heavy voltage fluctuations. Before connecting the amplifier to AC mains or battery operation make sure that: 1. The required Inputs such as microphones, cassette recorder etc. are firmly connected to Input jacks. The volume controls of the MIC/AUX are turned to "O" the MIC switches are at OFF position (see explanation on MIC/AUX operation)./  2. The group (s) loudspeakers are properly connected between COM and the matching output terminal. connections to be made only to one impedance at a time. Do not connect some speakers to 70V/100V Line and some to 4 ohms 8 ohms / 3. Master control should be at "O" (Flat) position.
24V-26V DC (Battery Operation): As "Stand-By" Power Source / The amplifier will also operate from an external DC supply (2 x12V Car batteries connected in series / As applicable). DC power connection should be made at the terminal strip marked (24VDC) on the rear panel. Make sure to observe correct battery polarity. The average current consumption on speech will be 5A, while on music it may rise to 6A at rated output. 
Simultaneous AC/dc Connections To Ensure Uninterrupted Service: The amplifier can be connected to AC supply and 24V battery simultaneously with power switch 'ON' In such case the amplifier will normally draw its power from AC mains only the battery power supply will act as a "stand-By". In case of electric failure or AC voltage dropping down abnormally, the amplifier will start drawing power uninterrupted. The amplifier will start operating on AC as soon as the AC supply is restored.

Overloading & Under loading

Never overload your amplifier by connecting loudspeakers / unit-horns to higher impedance taps than necessary as explained. Proper selection will fully safe guard the amplifier and output transistors from getting damaged.

Over loading: If the net resultant impedance of the group of loudspeakers, is say 4ohms and these are by mistake connected to “COM” and 8ohms tap, it will result in overloading (partial short circuiting )of the amplifier. The result will not only be bad quality of sound but likely damage to the amplifier. This must be avoided at all costs.  
Equal Matching : When the group (s) of loudspeakers having resultant impedance of 8ohms it will be equal matching. In this position, the amplifier will work at the rated efficiency and the best possible transfer of power from the amplifier to the loudspeakers will take place.
Under loading : When the same group (s) of loudspeaker is connected between "COM" and 4ohms tap, the transfer of power to speakers will be reduced to about 100 watts. However, in such condition of "Under loading" on loss of quality of sound reproduction occurs and no damage will be caused to the amplifier.  Therefore, the under loading connections can be useful where two or four units are to be connected with powerful amplifiers.   Important Service Hints  Method Of Replacing Transistors.  

Replacing Transistors
While replacing transistors please ensure the various mounting accessories of transistor are properly like 2N3773 and 2N3055H may result into overheating of power transistor, Hardware like MICA washer, Insulating bush etc, should also be replaced.  Application of heat sink compound properly also plays important pare. For correct application following procedure should be followed. 1. Clean mating surfaces. 2. Apply a small quantity of Heat Sink compound to both (Evenly Spread) surfaced to be mated. 3. Be sure there is no foreign objects in the compound such as brush hair. 4. Press surface together and squeeze out excess material.  5. Wipe excess compound, to help prevent dirt accumulation.
Adjustment Of No signal Current After changing Power Transistors  Following steps should be adopted : 1. Make all Control minimum including Master and Tone Controls.  2. Remove DC fuse & connect the Amp. meter having range capable to measure current up to 200mA. switch on the set and note the amp. meter reading. 3. The current should be between 165mA and 195mA In case it is beyond above range, then adjust this pre-set Power Transistor.

Precautions 1: 1.Before operating the amplifier, carefully read and fully understand the instructions. 2.Keep dry battery switch at OFF position when the amplifier is operating on AC or car battery. 3. Do not remove amplifier cover with AC mains connected. 4. In case any fuse blows, replace with another of the same rating. 5. Make certain that all input cables are kept away from speaker cables and power cables. Inputs should be securely connected to the amplifier. 6. Do not extend length of battery cable. 7. keep the amplifier in a dry and well ventilated place. 8. make sure that speaker cables are not shorting. Read instructions for speaker connections carefully before installing.  9.Use of low impedance microphone is recommended.

Precautions 2 : Speak with the microphone close to your mouth (one to two cams. from the lips). ensure that the holes on the back of the microphone are not covered in any way.2. Depress or lock the microphone switch ON only when actually making an announcement. Ensure that the microphone switch is on the OFF position when the megaphone is not actually in use. 3. Take out the dry cells when the megaphone is not to be used for long time. Warning : When MIC switch is kept locked in "ON" position the battery is being consumed continuously. switch it "OFF" when not in actual use.

Loss Of Power : Output In Cables 4ohms 8ohms 16ohms direct connections suffer from a serious disadvantage. On account of its being a low impedance, low voltage operation, heavy current has to flow through the cables/wires used for connecting the loudspeakers. Even when 23/36 PVC twin-flex wire is used but the speakers are placed at longer distance from the amplifier, an appreciable loss (wastage) of power results. For instance, if a driver unit is installed 50meters (160ft) away from the amplifier with 15watts power output being fed to it, only 10 watts will reach the terminals of the driver unit while 5watts will get wasted in the cables. Loss (wastage) becomes alarmingly high when 4 or more loudspeakers are connected to any of the 4ohms 8ohms 16ohms taps. Therefore where more than 4 speakers are to be installed, one must use line matching transformers or select the driver units with built-in line matching transformer like AU-40T

Tone Controls : The bass and Treble Controls should be individually set to the desired level as explained below.

Bass : This controls the tonal quality of low frequencies produced by musical instruments like Table/Drum etc. and to some extent male human voice. When this control is advanced towards Boost position, it will boost i.e. increase the intensity of the low frequencies. Similarly. when it is, lowered towards CUT position, it will cut i.e. reduce the intensity of low frequencies.

Treble : This controls the tone quality of instrument like Violin Sarangi and Sitar etc. and to some extent female human voice. When the control is advance upwards towards BOOST position, it will boost  i.e. increase the intensity of high frequencies, Similarly, when lowered. towards CUT position, it will cut i.e. reduce the intensity of high frequencies.

Mixing Facility : The signal from the two microphone, record player or tape can be mixed together by adjusting the respective volume controls to the desired level.

Line Output : A line output signal of 400mV can be taken out from the RCA jack at the rear. This output may be used for connecting additional higher wattage amplifiers for obtaining higher output power. The position of the tone control affects the tonal quality of the line output signal. 

Maintenance : To get a long trouble free service, maintenance is essential. After some use the Head, Capstan, Pinch Roller etc. which come in connect with the tape, become dirty due to dust or magnetic material on the tape. Dirty heads cause loss of high frequencies and the output falls. Dirty capstan and pinch roller will cause unstable tape speed, leading to increased Wow and Flutter.  

|| Amplifiers - Booster / Power / Two Zone / Instrument || Audio Mixer - Echo / Stereo || Conference Systems ||

 || Cassette - Player / Recorders / Preamplifiers || Driver Units || Horns - Reflex / Speaker || Microphones || Mobile PA || 

|| Speakers - Ceiling / Column / System / Wall / Professional || Sound System || Stand - Floor / Table / Accessories ||

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Due to continuous design & technical development specifications are subject to change without notice.