1、 Understand thefunctions of PCBA circuit board to be repaired:
At the beginning of circuit board maintenance, we needto know what equipment PCBA circuit board is used on and the fault phenomenon.
2、 Appearance inspectionfor circuit board maintenance:
Clean the PCBA circuit board with dirt on the surface,and carefully observe whether there are obvious damage phenomena such asmelting corrosion, wire breakage and short circuit on the front and back of thecircuit board, and whether the components are cracked.
3、 PCBA circuit boardmaintenance analysis:
Analyze the possible parts of the fault and formulatethe maintenance plan.
4、 Circuit boardmaintenance measurement:
1. Measure the electrostatic resistance between thepositive pole of the power supply and the ground of the circuit board to judgewhether the power supply is short circuited;
2. Use a multimeter to measure some discretecomponents, such as diodes, triodes, etc;
3. Conduct device function test with tester, and markthe test results one by one: good, bad and suspicious;
4. Conduct comparative test with ASA to further judgewhether 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 thoseon the fault board (record the name of the data file in the maintenance recordsheet);
5. Power up PCBA circuit board, measure whether thepower supply voltage is stable, and touch whether the device is overheated;Check the signal waveform of the device pin with an oscilloscope, such as thesignal on the bus and the clock signal of the CPU;
6. Various instruments measure alternately andcomprehensively analyze the test results to improve the accuracy of judgment;
7. Remove the devices marked "bad" and"suspicious" for offline test.
5、 Replace with newdevices:
Replace all removed devices with new ones, and installsockets after the devices on the multilayer board are welded off.
6、 Review:
After the installation of new devices, retest on themachine and conduct comprehensive inspection.
7、 Test plate:
If it does not return to normal, find out whether thefault phenomenon is the same as that before maintenance, and pay attention tothe new fault phenomenon. At the same time, understand the overall workingconditions and the electrical connection of peripheral interfaces for repair.
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