Public Broadcasting System Commissioning Test

- Oct 31, 2018-

The debugging of the broadcasting system mainly refers to the comprehensive and routine inspection of the equipment installation process after the installation and construction of the broadcasting system, and the opening test and sound quality evaluation. The main work contents are: transmission line inspection, mating inspection, insulation resistance. Measurement, grounding resistance measurement, antenna debugging, power supply test, system turn-on test, sound pressure measurement and sound quality evaluation, etc.

First, transmission line inspection

The broadcast transmission line is divided into indoor and outdoor wiring. When checking, the terminal of the line to be inspected should be disconnected from the equipment. Check whether the transmission wiring of each line is correct according to the construction drawing and the broadcast system diagram. Is there a short circuit? Faults such as open circuit and mixed line; whether the terminal number is complete and correct, and whether the terminal is soldered.

Second, the mating check

Check whether the matching of the inter-line transformers on each circuit or the speaker equipment is correct according to the construction drawing. In particular, the connection terminals of the multi-tap transformer are often easy to be connected incorrectly. Pay attention to check for missing and multiple connections, and the primary secondary connection phenomenon of the transformer. According to the diagram, check whether the transformer model, capacity and impedance match.

Third, the insulation resistance measurement

Disconnect the two terminals of the broadcast line and measure the insulation resistance between the lines with a 500V megger. Measure the insulation resistance of the line and the line and the ground, and the insulation resistance is generally not less than 0.5MΩ.

Fourth, the grounding resistance measurement

The grounding resistance of the broadcasting system is mainly performed on the grounding pole of the broadcasting room; the grounding resistance tester is used for the measurement. The power frequency grounding resistance of the broadcasting room amplifier, lightning arrester, etc. is generally not more than 10 Ω. When the capacity of the broadcasting system is above 150 W, if a grounding pole is set separately, it is possible to use a set of grounding poles with the electrical device, but this kind of grounding The required grounding resistance should not be greater than 4 Ω and a dedicated grounding trunk should be provided.

Five, power test

For the measurement of the AC power supply voltage, the power supply line should not be short-circuited or disconnected. Perform the on-off operation test on the power switch, check the power supply display signal; check the test of the standby power exchange device, measure the output voltage of the battery; The device performs inspection and measurement; performs a simulated power failure test to verify whether the power supply mutual investment device can work reliably.

Sixth, system opening test

1. Amplifier is turned on

First disconnect all output lines, pull out all input signal plugs, turn the amplifier's “volume” knob to the minimum, turn on the power, turn on the amplifier switch, observe whether the display signals are normal, and there is inorganic noise.

2. The preamplifier is turned on

When the amplifier is turned on and everything is normal, the preamplifier can be turned on. Turn on the preamplifier power supply, observe the various displays, and turn on the connection between the preamplifier and the power amplifier.

3. Microphone test

When the amplifier and preamplifier are working properly, turn the “amplifier” knob of the preamplifier and amplifier to the minimum, insert the microphone plug, give the microphone an audible signal, adjust the “volume” knob, and listen to the sound output on the monitor headphones. At this point, the “function” knob of the amplifier or preamplifier is turned to the microphone position.

4. Recorder input

Rotate the preamplifier or amplifier “function” knob to the recorder input and turn on the recorder input circuit, play the tape, adjust the “volume” size, and observe the input signal, distortion and noise.

5. Receive tuner open

Turn on the tuner power, receive the broadcast program, test the reception situation, and repeatedly adjust the direction of the FM receiving antenna according to the receiving effect of the FM radio to obtain the best listening effect. And observe the interference and distortion.

6. Output loop test

Input the preamplifier or amplifier into the recording or recording signal, turn the “volume” to the minimum, turn on the speaker device, turn the “volume” to the middle position, observe the volume, clarity and noise of the speaker; then turn the volume up to the maximum to see if there is distortion; adjust the speaker volume control to hear the sound distortion and volume changes. Speakers with severe distortion should check their line transformers and speaker coils, and if problems are found, they should be repaired or replaced.

 

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