How To Repair Common Faults Of Power Amplifier

How to repair common faults of power amplifier

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Update time : 2021-10-21 19:02:48
How to repair common faults of power amplifier
The machine does not work
1.Fault phenomenon: the fault that the whole machine does not work is that there is no display after the amplifier is energized. All function keys are invalid, and there is no sound, just like when the power is not on.
2.maintenance method: maintenance should first check the power supply circuit, switch on the power supply. Then use a multimeter to measure the dc resistance value at both ends of the power plug, which is normally several hundred ohms. If the gap is too large, and the power transformer is seriously hot, it means that the primary circuit of the power transformer has a local short circuit. If it is infinite, check whether the primary winding of the transformer is open, whether the fuse is broken, whether there is a break between the plug and the power line.

No sound output
1.Fault phenomenon: Silent fault is shown as corresponding state display but no signal output when operating each function key.
2.Maintenance method: When repairing the amplifier with protective circuit, it should be determined whether the protective relay can be closed after startup. If the relay does not operate, the overcurrent of the power amplifier at the middle point of the power amplifier circuit should be measured to detect whether the voltage is normal and the output voltage is offset. If the output voltage of the intermediate point is offset or the overcurrent detection voltage is abnormal, it indicates that the power amplifier circuit is faulty. Check whether the positive and negative power supplies are normal. If the positive and negative voltage is not symmetrical, the load circuit of the positive and negative power supply can be disconnected, so as to determine whether the power amplifier circuit is faulty or the power circuit itself is abnormal. If the positive and negative power supply is normal, the amplifier circuit should be checked whether the amplifier tube is damaged. 

Light sound
1.Fault phenomenon: light sound refers to the audio signal in
the process of amplification transmission, due to a large number of changes in the amplification stage or in a link is attenuated, so that the gain of the amplifier decreases or the output power becomes smaller.
2.Maintenance method: when maintenance, should check signal source and sound box is normal first, can use replacement method to check. Then check all kinds of conversion switches and control potentiometers to see whether the volume becomes larger. If everything is fine, it depends on whether the fault is in the front or rear circuits. For only one sound channel is light, the signal output of its front circuit can be exchanged and input to the back circuit of another sound channel. If the sound level of the speaker does not change, the fault will occur in the rear circuit.

The noise is large
1.Fault phenomenon: amplifier noise has alternating sound, cracking sound, induction noise and white noise.
2.Maintenance method: During maintenance, the noise should be judged first from the front stage or from the rear stage circuit. The signal connection plug of the front and rear stage can be removed. If the noise is significantly smaller, the fault is in the front stage circuit. Conversely, failure occurs in the rear circuit.

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