PCB Tech - Introduction to the steps and skills of circuit board repair technology

The introductory stage of PCB circuit board repair. First of all, you must be able to understand each electronic component in the circuit board, be familiar with the function and characteristics of each electronic component, the code in the circuit diagram and the circuit board, application, quality inspection, etc., and then master the circuit board Circuit structure, characteristics, performance parameters, failure mechanism, etc. Finally, master the use skills of commonly used instruments and maintenance tools, and then you can start to repair the circuit board.

Circuit board maintenance and training stage. This stage is a stage to improve circuit board repair skills, mainly in terms of repair speed. At this time, it is necessary to improve the knowledge of the composition, working principle, function, fault diagnosis process, and maintenance skills of various circuit structures in the circuit board. Grasp the basic wiring of each electronic component in the circuit board, draw the working principle diagram of the circuit board according to the actual object, and be able to analyze the ins and outs of the signal, the supply of power, and so on.

The actual stage of circuit board repair. At this stage, more hands-on repairs are needed to repair various faulty circuits. From the repairs, summarize the rules of fault occurrence, find faults skills, learn to write maintenance technical articles, etc., and accumulate a wealth of circuit board repairs by repairing a large number of faulty circuit boards. Experience, become a hardware maintenance engineer of the equipment weak current control system with excellent technology.

1. Look first and then measure: The circuit board to be repaired should be visually inspected first. If necessary, use a magnifying glass to observe. Mainly look at: 1. Whether there are broken wires and short circuits; especially whether the printed circuit board connecting wires on the circuit board are broken or stuck; 2. Whether related components such as resistors, capacitors, inductors, diodes, triodes, etc. exist Disconnection phenomenon; 3. Whether there are any problems such as false soldering, missing soldering, wrong insertion and wrong insertion.

3. First outside and then inside: When using the circuit online repair tester for testing, if the situation permits, it is best to have a good circuit board that is the same as the board to be repaired as a reference. Then use the double-bar VI curve scanning function of the tester to perform good and bad comparison tests on the two boards. The initial comparison test point can start from the port of the circuit board; then from the table to the inside, especially the comparative test of the capacitor. This can make up for the shortcoming that it is difficult for the multimeter to detect the leakage of the capacitor online.

4. Easy first and difficult later: In order to improve the test effect, before the online function test of the circuit board, some technical treatment should be done on the repaired board to minimize the impact of various interferences on the test process. The specific measures are as follows: a. Preparation before the test. Short-circuit the crystal oscillator. For large-capacity electrolytic capacitors, solder a pin to make it open. Because the charging and discharging of large-capacity capacitors will also bring interference. b. Use the elimination method to test the device. During the online test or comparison test of the device, if the device passes the test (or relatively normal), please directly confirm the test result and record it. If the test fails (or is out of tolerance), you can test it again. If it still fails, you can also confirm the test result first. This keeps testing until the devices on the board are tested (or compared). Then deal with those devices that fail the test (or are out of tolerance). c. Use the ASA-VI curve scan test to compare and test the devices that are not covered by the test library. Because the ASA-VI intelligent curve scan technology can be used to compare and test any device. As long as the test clamp can clamp the device, there is another reference circuit board. Through comparative testing, it also has strong fault detection and judgment capabilities for the device. This function makes up for the constraints of the insufficient device test library during the online function test of the device, and expands the detection range of the test instrument to the circuit board failure.

5. During the maintenance of PCB circuit boards, start statically and then move: For now, only functional online testing and static characteristic analysis of the components on the circuit board can be carried out. Therefore, whether the faulty circuit board is finally completely repaired, it must be installed back to the original equipment for inspection. In order to get the correct result of this inspection process, to judge whether the circuit board is repaired. At this time, it is best to first check whether the power supply of the device is correctly supplied to the circuit board as required, and whether all interface plug-ins on the circuit board are connected properly.