How to repair common faults of power amplifier
First, the whole machine does not work 1. Failure phenomenon The failure of the whole machine is that the amplifier has no display after power-on, each function key is invalid, and there is no sound, just like when it is not powered on. 2. Maintenance method During maintenance, you should first check the power circuit, turn on the power, and use a multimeter to measure the DC resistance value at both ends of the power plug. In normal times, the resistance value is several hundred ohms. If the gap is too large and the power transformer is extremely hot, it means that there is a local short circuit in the primary circuit of the power transformer. If it is infinite, check whether the primary winding of the transformer is open, whether the fuse is blown, and whether there is a break between the plug and the power line. This image was provided by a registered user '橘子 de 殿堂', Copyright feedback No sound output 1. Failure phenomenon Silent fault manifests as the corresponding status display when operating each function key, but no signal output. 2. Maintenance method When repairing the amplifier with protection circuit, it should be checked whether the protection relay can be pulled in after starting. If the relay does not operate, measure the mid-point power amplifier of the power amplifier circuit, whether the overcurrent detection voltage is normal, and whether the output voltage is shifted. If the midpoint output voltage shifts or the overcurrent detection voltage is abnormal, it means that the power amplifier circuit is faulty. Check whether the positive and negative power supplies are normal. If the positive and negative voltages are 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 supply circuit itself is abnormal. If the positive and negative power supplies are normal, check the amplifier tubes in the power amplifier circuit for damage. Third, light 1. Failure phenomenon Tone light refers to the fact that during the amplification and transmission of an audio signal, the gain of the amplifier is reduced or the output power is reduced due to a change in the amplification level of an amplification stage or attenuated at a certain stage. 2. Maintenance method When repairing, you should first check whether the signal source and speakers are normal. You can use alternative methods to check. Then check various transfer switches and control potentiometers to see if the volume can be increased. If all are normal, then it depends on whether the fault is in the pre-stage or post-stage circuit. For a single channel, the signal output by the pre-stage circuit can be exchanged and input to the post-stage circuit of the other channel. If the sound level of the speaker is the same, the fault is in the rear circuit. Fourth, noisy 1. Failure phenomenon The noise of the amplifier includes AC noise, popping noise, induced noise, and white noise. 2. Maintenance method When repairing, you should first determine whether the noise comes from the front stage or the back stage circuit. The front and rear signal connection plugs can be removed. If the noise is significantly reduced, the fault is in the front circuit. Otherwise, the fault is in the subsequent circuit. How to maintain the amplifier 1. The user should place the amplifier in a dry, ventilated place, and avoid working in humid, high temperature, and fume chemical agents. 2. The power amplifier should be placed on a safe, stable and hard-to-fall countertop or cabinet to avoid damage or fall to the ground, damage the machine or cause greater man-made disasters, such as fire, electric shock, etc. 3. The power amplifier should be avoided in the environment with serious electromagnetic interference, such as the radiated electromagnetic interference of fluorescent lamp ballasts will cause the CPU program of the machine to be disordered, resulting in the machine not working properly. 4. After the amplifier is used up, all function keys should be reset. If the function key is not reset for a long period of time, and its pull button spring is in a stressed state for a long time, it will easily cause malfunction. 5. Before turning on and off the audio power, you should turn the volume potentiometer of the amplifier to the minimum. This is one of the most effective protection methods for the amplifier and the speaker. At this time, the power amplification of the power amplifier is almost zero, and at least it will not cause harm to the speaker at the time of misoperation. 6, in the case of long-term non-use, especially in humid and hot seasons, it is best to power on for half an hour every day. In this way, the heat generated during the operation of the components inside the machine can be used to drive away moisture and prevent the internal coils, speaker voice coils, transformers, etc. from being damaged by moisture. 7. Wipe the surface of the machine with a clean, soft cotton cloth at regular intervals. When not in use, cover the machine with a dust cover or cloth to prevent dust from entering. 8. The normal working temperature of audio equipment should be 18 ℃ ～ 45 ℃. If the temperature is too low, the sensitivity of some machines will be reduced. If the temperature is too high, it is easy to burn out the components or cause the components to age early. In summer, pay special attention to cooling and maintaining air circulation.