PCB News - On-line measurement method of pcb board

On-line measurement method is generally applied to manufacturers of mass production PCB 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. The online measurement method mainly solves two problems. The first is to subdivide the problems found in the previous two steps, and finally lock the problematic components. The second is that the problem is not solved through the above two steps of inspection, and the cause of the fault needs to be found through online measurement. The online measurement method is mainly carried out through the following steps.

The first step: Power on the circuit board. In this step, it should be noted that some circuit boards are not a single power supply. They may require 5V, plus or minus 12V, 24V, and so on. Do not add the power supply that should be added. NS. After the PCB boards is powered on, touch the components on the circuit board by hand to see if there are hot components, and focus on checking the 74 series chips. If the components are hot, it means that the components may have been damaged. After replacing the components, check whether the PCB boards failure has been resolved.

Step 2: Use an oscilloscope to measure the gate circuit on the circuit board and observe whether it conforms to the logical relationship. If the output is not logical, it needs to be treated separately in two cases. One is that the output should be low level, and the actual measurement is high level, which can directly judge the chip damage; the other is that the output should be high level. The actual measurement is low, and it cannot be judged that the chip has been damaged. It is necessary to disconnect the chip from the following circuit, measure again, observe whether the logic is reasonable, and judge whether the chip is good or bad.

Step 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; if there is output, you need to put back the removed chips one by one, install one by one and test one to find out where the fault is.

The fourth step: Digital circuit with bus structure, generally including number, address, and control bus. Use an oscilloscope to measure the three-way bus, compare the schematic diagram, observe whether the signal is normal, and find out the problem.

On-line measurement method is mainly used to compare two good and bad PCB boards. Through the comparison, problems are found and solved. So as to complete the repair of the circuit board.

From the observation method, static measurement method and dynamic measurement, this article explains some methods and skills in circuit board maintenance step by step. With the development of modern technology becoming more and more mature, various new instruments and equipment are constantly emerging, and detection methods are also emerging in an endless stream. The original detection equipment and methods are less and less valued. But for a person engaged in electronic engineering, relying on simple testing tools, such as multimeters, oscilloscopes, etc. for measurement and maintenance, is still an essential skill for an electronic engineer.

The above is the online measurement method of PCB board. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.