SMT Component Failure
Some SMD components are very small, and it is inconvenient to use ordinary multimeter test leads to test and repair. One is easy to cause a short circuit, and the other is that it is inconvenient for the circuit board coated with an insulating coating to touch the metal part of the component pin. Here is an easy way to tell everyone, it will bring a lot of convenience to the detection.
Take two sewing needles of the smallest size and close them to the multimeter pen, then take a thin copper wire from a multi-strand cable, tie the test pen and the sewing needle together with a thin copper wire, and then solder firmly . In this way, there is no risk of short circuit when measuring those SMT components with a test pen with a small needle tip, and the needle tip can pierce the insulating coating and directly ram the key parts without having to bother to scrape the film.
Short-circuit Failure of Public Power Supply
In circuit board maintenance, if you encounter a short-circuit of the public power supply, the fault is often serious, because many devices share the same power supply, and every device using this power supply is suspected of short-circuiting.
If there are not many components on the board, the method of “hoeing the earth” can finally find the short-circuit point; if there are too many components, whether the “hoeing the earth” can hoe the situation depends on luck. A more effective method is recommended here. Using this method will get twice the result with half the effort, and the point of failure can often be found quickly.
It is necessary to have a power supply with adjustable voltage and current, voltage 0-30V, current 0-3A, this kind of power supply is not expensive, about 300 yuan. Adjust the open circuit voltage to the device power supply voltage level, first adjust the current to the minimum, add this voltage to the power supply voltage point of the circuit such as the 5V and 0V terminals of the 74 series chip, and slowly increase the current depending on the degree of short circuit.
Touch the device by hand. When you touch a device that heats up significantly, this is often a damaged component, which can be removed for further measurement and confirmation. Of course, the voltage must not exceed the working voltage of the device during operation, and the connection cannot be reversed, otherwise it will burn out other good devices.
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