1、 Understand the functions of PCBA circuit board to be repaired:
At the beginning of circuit board maintenance, we need to know what equipment PCBA circuit board is used on and the fault phenomenon.
2、 Appearance inspection for circuit board maintenance:
Clean the PCBA circuit board with dirt on the surface, and carefully observe whether there are obvious damage phenomena such as melting corrosion, wire breakage and short circuit on the front and back of the circuit board, and whether the components are cracked.
3、 PCBA circuit board maintenance analysis:
Analyze the possible parts of the fault and formulate the maintenance plan.
4、 Circuit board maintenance measurement:
Measure the electrostatic resistance between the positive pole of the power supply and the ground of the circuit board to judge whether the power supply is short circuited;
Use a multimeter to measure some discrete components, such as diodes, triodes, etc;
Conduct device function test with tester, and mark the test results one by one: good, bad and suspicious;
Conduct comparative test with ASA to further judge whether it is good or bad; If there is a programmable device or program memory, read out and store the contents of the good board and compare them with those on the fault board (record the name of the data file in the maintenance record sheet);
Power up PCBA circuit board, measure whether the power supply voltage is stable, and touch whether the device is overheated; Check the signal waveform of the device pin with an oscilloscope, such as the signal on the bus and the clock signal of the CPU;
Various instruments measure alternately and comprehensively analyze the test results to improve the accuracy of judgment;
Remove the devices marked "bad" and "suspicious" for offline test.
5、 Replace with new devices:
Replace all removed devices with new ones, and install sockets after the devices on the multilayer board are welded off.
6、 Review:
After the installation of new devices, retest on the machine and conduct comprehensive inspection.
7、 Test plate:
If it does not return to normal, find out whether the fault phenomenon is the same as that before maintenance, and pay attention to the new fault phenomenon. At the same time, understand the overall working conditions and the electrical connection of peripheral interfaces for repair.
Relying on the professional engineering team and the supply chain advantages of Guangdong, Hong Kong and Macao Bay area, baiqiancheng provides BOM cost optimization, risk control, alternative material suggestions, complete BOM procurement and other services to hundreds of customers every year. Professional BOM engineers, procurement engineers and IQC incoming material quality inspection control the quality of materials from the source, so as to avoid the quality risk of self purchased materials, reduce the procurement cost, shorten the procurement cycle, and provide strong support for customer R & D and proofing and small and medium-sized batch production. Establish long-term cooperative relations with many domestic and foreign electronic component manufacturers and brand authorized agents to solve customers' purchase needs for scarce materials, multiple batches and various materials.
