What if the amplifier has no sound output?
Equilateral Prism,Low Angle Prism,Optical Equilateral Prism,Optical Dispersing Prism Lambda Research Optics ChangChun,LTD. , https://www.lambdachina.com
When overhauling an amplifier with a protection circuit, it should be checked whether the protection relay can be switched on after starting up. If the relay does not operate, measure whether the midpoint output voltage of the power amplifier circuit is offset and whether the overcurrent detection voltage is normal. If the midpoint output voltage 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 voltages are asymmetric, the load circuit of the positive and negative power supply can be disconnected to judge whether the power supply circuit itself is abnormal or the power amplifier circuit is faulty. If the positive and negative power supplies are normal, check whether the amplifier tubes in the power amplifier circuit are damaged. If the midpoint output voltage and overcurrent detection voltage of the power amplifier circuit are normal and the protection relay does not pull in, the fault is in the protection circuit. Check whether the relay driver integrated circuit or the drive tube is damaged and whether each detection circuit is normal. If the relay contacts can be pulled, but no sound is output, check whether the speakers are normal, whether the relay contacts are in good contact and whether the squelch circuit is operating.
If the above parts are normal, then use the signal interference method to check the fault is in the amplifier after the class or the pre-level circuit. Use a multimeter R×1 gear to ground the red meter, and the black meter quickly touch the input of the rear amplifier circuit. If there is a strong “Titicaca†sound in the speaker, the fault is in the preamplifier circuit; if the speaker is not In response, the fault is in the post-amplifier circuit.
For integrated circuit power amplifier circuits that do not use peripheral protection circuitry (usually thermal protection inside the IC), the supply voltage can be measured first. If the supply voltage is normal, then use the signal interference method to check: Add the DC intermittent signal to the signal input terminal of the power amplifier integrated circuit. If the speaker has a strong “Titicaca†sound, it indicates that the power amplifier integrated circuit is normal and the fault is in the preamplifier circuit. If there is no "Titicaca" sound, and check that the relevant external components are also normal, the fault is in the power amplifier IC itself.
The tube amplifier has no sound output, and it should also check its power supply first to see if the filament is bright and the temperature of the bulb is normal. If the filament does not light, the tube is very cold, and check whether the filament of the power amplifier tube and the plate voltage are normal or not. If the voltage is abnormal, check the power circuit again. If necessary, disconnect the power load circuit to determine whether the power circuit is faulty or the load has a short circuit. If the voltage is normal, DC interference signal can be added to the center of the volume potentiometer. If there is a strong reaction, the amplifier circuit is normal and the fault is in the preamplifier circuit. Otherwise, the fault is in the amplifier circuit. An interference signal may be added to the gate of the boosting tube and the gate of the input amplification tube, respectively, and there is no response in which level plus interference signal, which indicates that the circuit behind the level is not working properly. Suspicious components (such as tubes) can be overhauled.
AV amplifiers with Dolby Surround decoding function, if there is no sound in the Dolby Surround sound state and each channel is muted and the main channel sounds in the straight-through state, the Dolby Surround decoding circuit is usually used when the power supply circuit is normal. Or the system control circuit is not working properly. If there is no sound in the surround and pass modes, check the system control circuit, signal selection circuit, and master volume control circuit.