Common PCB circuit board debugging skills

Whether it is a board made by others, or a PCB board designed and manufactured by yourself , the first thing to do is to check the integrity of the board, such as tin plating, cracks, short circuits, open circuits and drilling. Rigorous, then you can check the resistance value between the power supply and the ground wire by the way.

Under normal circumstances, the components of the do-it-yourself board will be installed after the tinning is completed, and if people do it, it is just an empty tinned PCB board with holes, and you need to install the components yourself when you get it. . Some people have a lot of information about the PCB board they designed, so they like to put all the components on it at one time and then test it. In fact, it is recommended to do it bit by bit.

PCB circuit board under debugging

New PCB board debugging can start from the power supply part. The safest way is to put a fuse on and then connect the power supply (it is best to use a regulated power supply just in case. Use the regulated power supply to set the overcurrent protection currect, and then slowly increase the voltage of the regulated power supply upward. This process requires monitoring the input current, input voltage and output voltage of the board.

When the voltage is adjusted upward, there is no overcurrent protection and the output voltage is normal, then it means that there is no problem with the power supply part of the board. If the normal output voltage or overcurrent protection is exceeded, then the cause of the fault must be checked.

PCB circuit board component installation

Install the modules gradually during the debugging process, and follow the above steps for testing each time one or several modules are installed, which is beneficial to avoid some hidden errors at the beginning of the design, or errors in the installation of components, resulting in overcurrent burnout bad components.

If there is a failure during the installation process, generally use the following methods to troubleshoot:

Troubleshooting Method 1: Voltage Measurement Method


Measuring voltage method

When overcurrent protection occurs, do not rush to disassemble the components, first confirm the voltage of the power pins of each chip to see if it is within the normal range. After that, the reference voltage, working voltage, etc. are detected in turn. For example: when the silicon triode is turned on, the voltage of the BE junction will be about 0.7V, and the CE junction is generally 0.3V or less. When the BE junction voltage is found to be higher than 0.7V during the test (special transistors , such as Darlington are excluded here ), then it is possible that the BE junction is open. Follow the method and check the voltage at each point to eliminate the fault.

Troubleshooting Method 2: Signal Injection Method

signal injection

The signal injection method is more troublesome than measuring the voltage. When sending the signal source to the input end, we need to measure the waveform of each point in turn, and find the fault point from the waveform. Of course, you can also use tweezers to detect the input terminal. The method is to touch the input terminal with tweezers, and then observe the response of the input terminal. Generally, this method is used in the case of audio and video amplifier circuits (Note: hot floor circuit and high voltage circuit) Do not use this method, it is prone to electric shock accidents). The method detects that the previous stage is normal, and the latter stage has a response, then the fault is not in the latter stage, but on the previous stage.

Troubleshooting Method 3: Others

PCB circuit board appearance inspection machine

The above two are relatively simple and direct methods. In addition, for example, seeing, smelling, listening, touching, etc. are often said, only engineers who need some experience can detect the problem. Generally, "look" is not to see the state of the testing instrument, but to see whether the appearance of the components is complete; "smell" is mainly to smell whether the smell of the components is abnormal, such as burnt smell, electrolyte and other smells. Generally, the components are in the There is an unpleasant burnt smell when damaged.

And "listening" is mainly to listen to whether the sound of the board is normal under the working state; about "touching", it is not to touch whether the components are loose, but to feel whether the temperature of the components is normal, for example, under the working state, the cold The components are hot, and the components that are hot are extremely cold. In the process of touching, do not directly pinch it with your hands to prevent the hand from being scalded by the high temperature.