Should follow the following principles and steps, in an orderly manner.
Principle one, look at the amount
Use tools: multimeter, magnifying glass
When holding a circuit board to be repaired, good habits should first of all be dealt with visually and, if necessary, with a magnifying glass to see what?
1, whether there is a broken line;
2, components of components such as resistance, electrolytic capacitors, inductors, diodes, transistors, etc. there is a disconnect;
3, Printed circuit board connector is broken, adhesions and so on;
4, whether someone repair it? Moved what components? Whether the existence of Weld, leak welding, inserted reverse and other operational errors;
After confirming the above conditions have not been repaired, first with a multimeter to measure the resistance between the circuit board power and ground, the circuit board resistance are usually 70-80? Above, if the resistance is too small, only a few or a dozen ohms, indicating that the circuit board components have been breakdown or partial breakdown, we must take measures to be breakdown of the components to find out. The specific method is to be board power supply, touch the circuit board by hand to each device
Temperature, hot lecturer focus suspects. If the resistance is normal, with a multimeter measuring board resistance, diodes, transistors, FETs, dial switches and other components of force, the purpose is to ensure that the first measurement of the components is normal, our reason is that can be used Multimeter to solve the problem, do not make it complicated.
Principle two, first outside after
Use tools: HY circuit online repair instrument
If possible, it is best to find a good plate that is the same as the plate to be repaired, and then use the double rod VI curve scanning function together to perform good and bad contrast tests on both plates. The starting point of comparison can start from the port , And then from the table, especially the comparison of the capacitance test, you can make up for the multimeter online difficult to detect whether the leakage of defects.
Principle three, the first easy and difficult
Use tools: HY circuit online repair instrument, electric iron, marker
In order to improve the test result, some technical processing should be done on the board before the on-line functional test is performed on the circuit board so as to weaken the negative influence of various interference on the test process as much as possible. Specific measures are:
1, before the test preparation
The crystal short circuit, a large electrolytic capacitor to be welded to the next foot open, because the charge and discharge capacitors also can cause interference.
2, using exclusion method to test the device
In the process of on-line testing or comparison of devices, please pass the test (or more normal) devices, please confirm the test results directly to record; If the test fails (or compare tolerance), can re-test again, if still not Pass, or confirm the test result, so test until the device on the board is tested (or compared) and then go back to the device that failed the test (or compare the tolerance). The instrument also provides a less formal but more practical treatment for devices that fail to pass the function test online (Source: http: //www.dqjsw.com.cn/) Since the instrument power to the board can Through the test clip applied to the device corresponding to the power and ground, if the device’s power pin blade, then the device will be detached from the circuit board power supply system, then the device for online functional testing, the circuit board due to other The device will no longer play a disturbing role, the actual test results equivalent to “quasi-offline”, the accuracy rate will be greatly improved.
3, using the ASA-VI curve scan test to test the device has not been covered by the comparison test
As the ASA-VI smart curve scanning technology can be applied to any device to compare the test, as long as the test clip can clamp the device, then a reference board, through the comparison test, the same device has a strong fault detection capability. This function makes up for the lack of testing function of the device on-line function test and expands the detection range of the instrument on the circuit board failure. In reality, there are often situations where a good board can not be found for reference, and there is no symmetry in the circuit structure of the board to be repaired. In this case, the ASA-VI curve scan comparison test function does not work, and the online function test Because the device test library is not complete, can not be completed on the circuit board for each device are tested again, the circuit board still can not be repaired, here is the limitations of the circuit repair instrument, just as there is no cure for the same.
Principle four, the first quiet move
At present, the on-line repair instrument of the circuit can only perform on-line test and static analysis of the functions of the devices on the circuit board. Whether the device is fully repaired or not must go through the whole machine test and inspection. Therefore, it is best to check whether the power of the device is as required Correct supply to the board.