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When repairing the circuit board what should pay attention to

In the absence of any schematic diagrams, it is difficult to deal with an unfamiliar and complicated faulty circuit board. The so-called “overhaul experience” in the past is difficult to cope with. What can be done to improve maintenance efficiency?

First look then measure

The board to be repaired should first be visually inspected. If necessary, observe with a magnifying glass.

Mainly look at:

1. Is there any broken wire or short circuit; especially if there is crack or adhesion on the printed circuit board connecting line on the circuit board;
2. Whether there are disconnections in components such as resistors, capacitors, inductors, diodes, and triodes;
3. Has anyone repaired it? What components have been dealt? Whether there are problems such as virtual welding, missing welding, pluggingreverseand inserting errors.

Second, the first outside then inside

When using the maintenance tester for testing, it is best to have a good circuit  board as the reference which is same as the repaired one, if possible. Then use the tester’s double-bar VI curve scan function to perform good and bad comparison tests on the two circuit boards. The starting comparison test point can start from the port of the circuit board; then it is tested by comparison from the outside to the inside, especially for the capacitor. This can make up for the shortcomings in the multimeter that it is difficult to measure whether the capacitor is leaking.

Third, the first easy then difficult

When using the maintenance tester for testing, in order to improve the test effects, before the online functional test of the circuit board, the technical processing of the repaired board should be done to minimize the impact of various interferences on the test process. The specific measures are as follows:

1. Preparation before testing

The crystal is short-circuited, and for large-capacity electrolytic capacitors, the foot is also soldered to open the circuit. Because the charging and discharging of large-capacity capacitors also cause interference.

2. 2.Using the exclusion method to test the device

During the online test or comparison test of the device, if the device passes the test (or is relatively normal), please confirm the test result directly and record it. If the test fails (or is relatively poor), you can test it again. If it still fails, you can confirm the test results firstly. This is tested until the all devices on the board are tested (or compared). Then deal with those devices that fail the test (or compare the out-of-tolerance).

3.Compare tests with devices not covered by the test library using the ASA-VI curve scan test

Because ASA-VI smart curve scanning technology can be applied to the comparison test of any device. As long as the test clip can clamp the device, there is another reference circuit board. Through comparison tests, the device also has strong fault detection and judgment capabilities. This function compensates for the insufficiency of the device test library when the online function test of the device is made, and expands the detection range of the test instrument for the board fault.

Fourth, first static and then move

Since the maintenance tester is currently available, functional online testing and static feature analysis can only be performed on devices on the board. Therefore, if the faulty circuit board is finally completely repaired, it must be loaded back to the original equipment for inspection. In order to get the correct result of this inspection process, to judge whether the board is repaired. At this time, it is best to check whether the power of the device is correctly supplied to the circuit board as required, and whether the interface plug-ins on the circuit board are properly connected. Be sure to eliminate the effects of incorrect environment around the board and peripheral circuitry.