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    Circuit online maintenance instrument maintenance principle for circuit boards


    In the absence of any schematic diagrams, it is necessary to repair a relatively unfamiliar circuit board. The so-called “experience” in the past is difficult to do. Although people with deep hardware skills are full of confidence in maintenance, if the method is not right, it will work twice as well.Principle 1, first look at the amount of use Tools: multimeter, magnifying glass When holding a circuit board to be repaired, good habits should first be visually measured, if necessary, with the aid of a magnifying glass,Insertion and other operations errors; After determining that the above conditions are not repaired, first use a multimeter to measure the resistance between the power supply of the board and the ground. Usually, the resistance of the board is above 70-80?Too small, only a few or a dozen ohms, indicating that components on the board are broken down or partially broken down.If the resistance is normal, use a multimeter to measure the components such as Resistorss, diodes, triodes, FETs, and dial switches on the board. The purpose is to ensure that the measured components are normal.

    Our reason is that they can be used.Don’t complicate the problem solved by the multimeter.In particular, the comparison test of the capacitor can make up for the shortcoming that the multimeter is difficult to measure whether it is leaking.The specific measures are as follows: 1. Preparation before testing Short-circuit the crystal oscillator, and solder a foot to the large electrolytic capacitor to open the circuit, because the charging and discharging of the capacitor can also cause interference.This is the case until the devices on the board are tested (or compared) and then returned to handle those devices that have failed the test (or are out of tolerance).At this time, the device is tested for online function. Since other devices on the board will not interfere again, the actual test result is equivalent to “quasi-offline”, and the precision will be greatly improved.This function makes up for the shortcomings of the online functional test of the device subject to the test library, and expands the scope of detection of the board fault.It is impossible to complete testing each device on the board, and the board still cannot be repaired. This is the limitation of the circuit online maintenance instrument, just like the medicine without cure.


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