Need the tools are multimeter, electric iron, blade, tweezers.
Judgment of the problem must be the first way after the main treatment, will be obvious, serious first treatment, small problem post-processing. The short circuit should be the highest priority.
1 observation, observation and visual inspection of the screen, and sometimes open the eyes can be seen with the eyes, such as PCB lines due to scratch, so that the circuit, and sometimes accidentally broken electric drill!
2 contrast method, the contrast is very important and very critical, sometimes IC we can not see whether it is burned, you can use a good IC replacement, and sometimes we do not remember whether the signal is the same, we can take a good cell board measurement What is the corresponding position below! Contrast is critical!
3 exclusion, and sometimes a failure there are many reasons, we can one by one to deal with, do not remember you can look at the front of the common fault handling, one by one excluded!
4, the resistance test method, the multimeter transferred to the resistance file, a normal circuit board to detect a point to the ground resistance value, and then detect another piece of the same circuit board with the normal resistance of the same test value is different, If different, to determine the scope of the problem.
5, the voltage detection method, the multimeter transferred to the voltage file to detect the suspected circuit of a certain point to the ground voltage, compared with the normal value is similar, or to determine the scope of the problem.
6, short-circuit detection method, the multimeter transferred to the short-circuit detection block (some diode downshift or resistance file, generally with alarm function), to detect whether there is a short circuit phenomenon, found after the short circuit should be addressed first, so that Other devices. The method must be operated in the case of circuit power failure to avoid damage to the table.
7, the pressure drop detection method, the multimeter transferred to the diode voltage drop detection file, because all the IC is composed of a large number of single components, but miniaturization, so when it has a current through a pin, There will be a voltage drop on the pin.