Analysis of Causes of Common Faults in Electronic Circuits

First, common fault phenomena


The amplifier circuit has no input signal and has an output waveform.

The amplifier circuit has an input signal, but there is no output waveform, or the waveform is abnormal.

The series regulated power supply has no voltage output, or the output voltage is too high and cannot be adjusted, or the output voltage regulation performance is deteriorated, and the output voltage is unstable.

The oscillating circuit does not oscillate.

The counter output waveform is unstable or cannot be counted correctly.

In the radio, there are "嗡嗡" hum and "啪啪" steamboat sounds.

These are some of the most common failures, and there are many strange phenomena that are not listed here.

Second, the cause of the failure


There are many reasons for the failure, and the situation is very complicated. Some are simple faults caused by one cause, and some are complex faults caused by interactions of various reasons. Therefore, the cause of the malfunction is difficult to classify simply. Only a few rough analysis can be done here.

1. For a certain period of time after the use of the shaped product, the fault may be due to component damage, short circuit or open circuit (such as solder joint solder joint, poor connector contact, variable resistor, potentiometer, semi-variable resistor) Such as poor contact, oxidation of the surface of the contact surface, etc., or changes in the use conditions (such as grid voltage fluctuations, super-cold or overheated working environment, etc.) affect the normal operation of electronic equipment.

2. For newly designed and installed circuits, the cause of the failure may be: the actual circuit does not conform to the schematic of the design; the components are improperly used for damage; the designed circuit itself has some serious shortcomings that do not meet the technical requirements; Short circuit or open circuit, etc.

3. Faults caused by incorrect use of the instrument, such as abnormal or no waveform caused by incorrect use of the oscilloscope, and interference caused by improper handling of the grounding problem.

4. Faults caused by various disturbances

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