The Specific Methods of Judging the Failure of the Printed Circuit Board
Nowadays, printed circuit boards make circuits miniaturized and intuitive, which plays an important role in the mass production of fixed circuits and optimizing the layout of electrical appliances. Moreover, the printed circuit board is composed of many electronic components, such as capacitors, resistors, diodes, etc. When the circuit board fails, we need to use the following methods to determine the point of failure.
Observation
This method is quite intuitive, and through careful inspection, the burnt traces can be clearly seen. When using this method, you need to pay attention to the following issues:
1. Determine whether the circuit board is artificially damaged by observation, mainly by observing the following aspects to determine:
(1) Whether the corners of the board are deformed; whether the chip is deformed, and whether other components are deformed.
(2) Whether there are any signs of prying on the chip and socket.
(3) Whether the corresponding short-circuits terminal of the circuit board is inserted incorrectly or reversed.
2. Carefully observe the related components of the printed circuit board, every capacitor, resistor, etc. must be observed to see if there is any blackening. Since the resistance cannot be viewed, it can only be measured with an instrument, and damaged accessories should be replaced in time.
3. Observation of circuit board integrated circuits, such as CPU, AD, and other related chips, if bulging, burning, and other related conditions are observed, it should be repaired in time.
Static measurement
In maintenance, it is often difficult to find some problems with the observation method, unless it is obvious that it is burned or deformed. But most of the problems still need to be measured by a voltmeter to reach a conclusion. Therefore, the components and related parts of the circuit board must be tested one by one. The main tool is a multimeter, and the process is as follows:
1. Detect the short circuit of the power supply and check the reason.
2. Check whether the diode is normal.
3. Check whether there is a short circuit or even an open circuit in the capacitor.
4. Check the circuit board-related integrated circuits and resistors and other related device indicators.
The observation method and static measurement method can solve most of the problems in circuit board maintenance, but during the measurement, ensure that the power supply is normal and no secondary damage can occur.
Online measurement
The online measurement method is generally applied to manufacturers of mass production circuit boards. For the convenience of maintenance, manufacturers generally build a more general debugging and maintenance platform, which can conveniently provide the power supply required by the circuit board and some necessary initial signals.
1. Power on the circuit board. What needs to be noted in this step is that some circuit boards have different power supplies. After the circuit board is powered on, touch the components on the circuit board with your hands to see if there are any hot components. If the component is hot, it means that the component may have been damaged. After replacing the components, check whether the circuit board failure has been resolved.
2. Measure the gate circuit on the circuit board with an oscilloscope to observe whether it conforms to the logical relationship.
3. Use an oscilloscope to measure the crystal oscillator in the digital circuit to see if it has an output. If there is no output, you need to remove all the chips connected to the crystal oscillator as much as possible before measuring. If there is still no output, it is preliminarily determined that the crystal oscillator has been damaged.
4. Measure the three-way bus with an oscilloscope, compare the schematic diagram, observe whether the signal is normal, and find out the problem.
Through the above measurement methods, we can accurately find out where the printed circuit board failure occurs and carry out effective maintenance. If you want to learn more about printed circuit boards after reading the above content, you can get a comprehensive solution by contacting PCB Quick.
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