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What are the fault analysis and elimination methods of public broadcasting power amplifier?


  basic processing method of power amplifier machine:

No electricity: check whether the power line is connected to the fuse tube, whether the power line is broken or the fuse tube is in poor contact, and the fuse tube is blown → check whether the rectifier bridge or electrolysis and other components of the power amplifier rectifier power supply are broken, such as the rectifier diode or bridge stack is broken and replace with good components, then check other lines, such as the power amplifier tube, etc.

The signal level indicator light flashes normally but no sound output: first check whether the speaker unit is normal. if it is normal, check whether the speaker lead is normal, that is, check whether the terminal contact is good and normal, that is, open the case by visual inspection or ear inspection to see whether the output relay is closed or not. if it is closed normally, (if there is a universal meter), that is, measure whether the front input end and output end of the relay are straight through, if not, the contacts in the relay oxidize or spark to cause carbon, that is, the relay is normal.

The power lamp indicates that there is no sound output normally, but the sound of the output relay is heard: first use a universal meter to measure whether the power supply of the power amplifier is normal. if it is normal, that is, the signal line terminal of the signal input terminal is connected with the hand. if it hears a large current sound, it is preliminarily judged that the power amplification part is basically normal, that is, if the signal lead is shaken lightly, it is unable or has poor contact, that is, when measured with a universal meter, it is normal to deal with the fault of that line.

If there is no sound output when the power amplifier outputs: check that the speaker unit is normal, if there is no poor contact between the terminals and cause scorching, if the terminals are burned black, clean up to ensure normal contact, and tighten the screws.

The start-up protection light is on: first, use a universal meter to measure whether there is a short circuit in the horn group and whether the resistance is reduced (generally, the normal value is not less than 30Ω). if the resistance of the external circuit of the machine is normal, it is judged that the power amplifier is faulty, and it is necessary to start up and check.

  The possibility of the phenomenon of loud and small sound lies in:

1. Poor contact of signal line;

2. Poor contact of potentiometer;

3. Signal coupling capacitance;

4. Poor contact of feedback resistor, etc.

In the measurement of power amplifier motherboard under normal circumstances no sound:

1. The signal line is not connected or the coupling capacitor is open;

2. Front without power supply, measuring power supply part;

3. The volume potentiometer is broken;

4. This fault will occur when the operational amplifier IC is bad.

Such as pure amplifier sound distortion, the part of the fault:

1. Soft breakdown of power tube;

2. The positive and negative voltage has no voltage or becomes low;

3. Resistance variable value, etc.

The sound normal level indicator does not operate:

1. First measure whether the voltage is normal;

2. Whether the re-measurement signal is sent;

3. Measure whether the components are damaged.

treble bass can't adjust:

1. Whether the potentiometer is normal;

2. Whether the voltage is normal;

3. Whether the RC element is normal;

4. Whether the line is connected or in poor contact;

5. Whether there is virtual welding, false welding and other phenomena in the welding spots.

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