Techniques for Equipment Maintenance of Sound Amplifying System

- Aug 20, 2018-

The sound reinforcement system consists of sound reinforcement equipment and sound field components, including the sound source and the acoustic environment around it, the microphone that converts the sound into electrical signals, the equipment that amplifies the signal and processes the signal, the transmission line, and the speaker that converts the signal into an acoustic signal and the acoustic environment of the audience area.

First, the visual inspection method

The visual inspection method is performed immediately after the power is turned off. Without the use of instruments and instruments, with the intuitive feeling, four kinds of sensory characteristics such as sight, hearing, smell and touch are mobilized to judge. Although this method of inspection is less accurate, it is fast, and the visual inspection method is especially useful for power failure checking.

A look at the machine or component and its external structure. Look at whether the button switch, interface, indicator light is loose, whether the circuit board is disconnected, whether there is any solder joint, discoloration, crack, burst, etc., whether the fuse is burnt, fire, smoke, deformation, not stuck Other issues, using the eyes, direct identification and judgment.

Gently flip the machine or parts, swing and sway, and hear if there are any parts scattered or the screws are falling off, and there is a click sound. For continuous flipping, there is no abnormal "beep" sound or "beep" sound (when energized). If these phenomena occur, malfunctions may occur in these places.

Smells. Use the nose to smell the smell of burning, find the source of the smell, the fault may be a place to release the smell.

Touches. Touch the transformer case by hand (after power off), do not touch the terminal block, because sometimes due to the presence of charging capacitors, the voltage is very high, endangering safety. Feel if it is above normal temperature, hot, and can't be touched. Whether the power tube is overheated or cold. Adjust the tube for overheating or cold and not hot. If there are these phenomena, the problem may appear in these places.

Second, the test method

The heuristic method is to use the heuristics of comparison, segmentation, substitution, simulation, etc. for the suspected part of the circuit to find the fault and then eliminate it. The specific method is as follows:

Compare a machine of the same type as the faulty machine. Use the left and right channel components of the same machine in professional equipment to measure the voltage, resistance and current of the corresponding part, and then compare and find the fault. .

Dividing. Disconnect a part of the circuit from other parts, connect the external power supply, and inject the signal to judge.

Replacement. Replace the suspect component with a good component, or swap the left and right channel components, especially for integrated circuit blocks. If the machine returns to normal after the part is swapped, there is a problem or damage to the part.

Simulate. Temperature simulation, use hair dryer to heat, or use alcohol to cool down, perform temperature performance check. Vibration simulation is to use light plastic insulation rod to tap some components to see the working condition of the circuit, you can find some solder joint phenomenon. Check for the fault. This method is generally performed by a skilled person; otherwise, it is prone to failure.

Third, static parameter measurement method

The measurement of static parameters must hold the maintenance manual of the manufacturer's production equipment, indicate the static working current or voltage of each component end point, and use the multimeter to measure the current, voltage or resistance value of each part of the circuit to see if it matches the nominal value.

Resistance measurement

Use the multimeter's ohmic file ×100 or ×1K file, do not use R × 10K file, because this file is connected to the 22.5 volt battery, it is not suitable for transistor measurement, it is easy to damage the transistor. In the case of power failure, if there is a charging capacitor, it must be fully discharged with an insulated screwdriver. The resistance in the measuring circuit must be welded to one end; otherwise the measurement is not accurate.

Voltage measurement

In the measurement process, the influence of the internal resistance of the multimeter on the measured value should be considered. It should be noted that the static measurement is not the same as the dynamic measurement (when the signal is added). When measuring static, the voltage of each transistor pin, resistor and capacitor terminal is consistent with the nominal value, and the relative voltage of the transistor pin can judge whether the tube is damaged.

Current measurement

When using direct measurement, string the ammeter into the circuit and check the current. When indirect measurement is used, the voltage across the two ends is measured, and the voltage value is removed by the resistance value to obtain the current value.

In addition to static parameter measurement, dynamic inspection can also be used. Signal sources and oscilloscopes can be used to directly inject signals to judge the circuit. This method is straightforward, accurate, and does not easily damage components, as well as adjustments and proofreading of circuits and mechanical structures.

 

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