Six ways to check the failure of the circuit board

Repair masters the most headache is estimated to be the circuit board failure repair work, in addition to the circuit board above the many components, PCB board circuit is dense is also a difficult problem. The following Shenzhen Qinji Electronics organized the circuit board to check the failure of the six methods, I hope to be able to help you!

First, the observation method

This is mainly in the inspection and maintenance process, the use of look (eyes) smell (nose) ask (ears to listen to the sound) cut (touch with your hands) can directly observe the electronic products and their components whether there is an error damage judgment method.

a. Observe whether there are foreign objects on the circuit board, such as metal foreign objects, welding beads, dirt, water vapor, etc..

b. Observe whether the electrolytic capacitor leakage, blow-up, electrolyte outflow.

c. Whether the resistor is burnt black or burnt off.

d. Whether the fuse, insurance resistor is burned out, whether the fuse glass tube is gray or black.

e. Power on the test machine, observe the circuit components in contact with the parts of the fire, sometimes see the point line sparks or smoke.

f. PCB circuit board copper foil is broken or warped.

g. Connect the wires or wires are disconnected or poor contact.

h. Use the nose to smell, you can smell the surface of the electronic components burnt paste odor. Inspection process, if you smell abnormal paste odor, you should quickly turn off the power to avoid the expansion of the fault.

i. Use your ears to listen. Let the electronic products on the power, in the work with the ear to listen to whether the "squeak", "popping" sound. j. Hand touch, please turn off the power.

j. When touching with hands, please turn off the power to ensure safety.2 oz copper thickness in mm Mainly to check whether the component contact is poor or whether there is overheating.

Second, resistance method

With the multimeter resistance gear to measure the circuit of suspicious points or suspicious electronic components, as well as PCB circuit board integrated circuits in the feet of the ground resistance, and the normal value of the relative comparison. The method can directly measure whether the resistance value, capacitance and other electronic components are short-circuit breakdown, whether there is an open circuit, short-circuit phenomenon, whether there is poor contact and whether the copper foil on the circuit board is broken. Resistance measurements are usually made in-circuit and open-circuit. Measurement in the road is in the circuit board directly measure the resistance of some electronic components, about clear fault areas, such a measurement method and the actual situation being measured resistance has a certain degree of error. Open-circuit measurement is the electronic components and PCB circuit board off or remove the measurement, so the measurement method is relatively accurate. In practice, basically using open-circuit measurement, especially for a part of the circuit parameters are not familiar with the case, usually remove the electronic components.

Third, the voltage method

Voltage method is in the case of power, with a multimeter voltage file to measure the voltage of the key points in the circuit or the working voltage of an electronic component, the measured value and the normal value of the relative comparative analysis to determine the fault of a method.plated through hole vs via Voltage measurement method is relatively simple and convenient. Can be divided into two ways of static and dynamic measurement method: static measurement method is in standby when the circuit has no signal input, that is, the static voltage measured; dynamic measurement method is in the case of power on, the circuit is in operation under the condition of the measured voltage.

Fourth, the current method

Current measurement method is to measure the entire equipment circuit, integrated circuits and transistors, the size of the operating current and the normal value of a relative comparison method. Special attention: in the detection of DC current should pay special attention to the positive and negative poles and range! In practice, according to the size of the measured current, you can judge the circuit, the operating state of the appliance.

Fifth, the substitution method

In short, the substitution method is to replace the suspected damage to electronic components with good electronic components to troubleshooting a method, this method is usually used for the multimeter is not good or can not measure the electronic components. In addition, when using the substitution method must ensure that the replacement of electronic components must be good, in order to prevent misjudgment.

Sixth, the open circuit method

An electronic component in the circuit or a part of the circuit and the circuit board off, while observing the relevant voltage, current, resistance and other measurements of the change or failure phenomenon disappears, and then determine the location of the fault of a method. For example, to check whether the load of the power supply is short-circuited, just disconnect the load and power supply can be judged.