How many methods do you know about electronic circuit fault detection?

The troubleshooting of electronic circuits can generally be detected by the input to the input sequence, or the reverse method from the output to the input. No matter which direction you start, electronic circuit fault detection can generally be judged by the following eight methods.
01 Direct observation
When a circuit breaks down, it is usually not used immediately to measure it, but to look for possible abnormal parts of the circuit with naked eyes. The direct observation method is divided into no-power and power-on detection.
No-power detection is to check whether the level and polarity of the power supply voltage meet the circuit requirements; the polarity of the electrolytic capacitor, the pin position of the diode and the transistor, and the pin position of the integrated circuit are there any problems such as false soldering, wrong soldering, and crossover. ;Whether there is an unreasonable place in the wiring; Is there any circuit breakage when the printing plate is printed; The resistance and the capacitor are obviously scorched.
And the power-on inspection is mainly to observe whether the components are overheated, smoke and obvious burnt smell, and whether the filaments of the electron tube and the oscilloscope tube have high-pressure ignition problems.
02 Multimeter test
Multimeter detection is mainly to check the static operating point, in which the resistance value and DC working status of the power supply system of the electronic circuit, the transistor, the integrated block and the circuit can be detected by the multimeter. Check to see if the value is normal.
03 signal tracking method
In a complex circuit, you can connect a signal to the input terminal, and then use an oscilloscope to observe the waveform and amplitude changes from the front stage to the back stage or from the back stage to the front stage, and finally see what is abnormal.
04 Comparison method
The 　　 comparison method is more intuitive, mainly by comparing the suspected fault circuit with the same circuit in normal working condition to find out whether there is a value with a large parameter difference, and then analyze the cause of the fault, and always judge the fault location.
05 substitution method
For electronic circuits with unobvious failures, when it is impossible to make intuitive judgments or suspected failure points, the same existing components can be used to replace them, and the fault judgment direction can be shortened by replacing and observing whether the circuit changes.
06 Bypass inspection method
If there is parasitic oscillation in the circuit, you can use a capacitor of a certain capacity to connect the capacitor across the place to be checked or between the reference grounding point, and then observe whether the oscillation exists. If the oscillation disappears, it means that the oscillation is generated before. Level circuit or nearby circuit. If not, move back and continue to look for checkpoints. When choosing a capacitor, care should be taken that the bypass capacitor should not be too large, as long as it can eliminate unfavorable signals.
07 short circuit inspection method
The 　　 short-circuit inspection method is that we take the initiative to create a temporary short circuit, so that some circuits are short-circuited. As shown in the above picture, the amplifier circuit, where the multimeter measures the voltage of the collector of T2 to the ground as 0. Then we suspect that the L1 circuit is open, and then make a temporary short circuit at both ends of L1. At this time, if the value of VC2 is normal, it means that the fault is on L1.
It should be noted that the short-circuit method cannot be used on the power circuit, so remember.
08 open circuit inspection method
The short-circuit method mentioned above is effective for checking the open circuit. Similarly, the short-circuit check by the open circuit method is also effective. The thinking of the open circuit inspection method is similar to the previous methods, which is used to eliminate doubts and shorten the scope. Assuming that the regulated power supply is connected to a faulty circuit, and the output circuit is too large at this time, then if we disconnect a certain part of the circuit in turn, then observe the current output of the circuit to determine the branch where the fault occurs.
The eight kinds of appeals are actually just some of the more commonly used methods. There are many ways to judge the fault, which can be flexibly applied through different instruments and equipment, so that it will be easier to judge complex faults.