(1) Short circuit detection method
Adjust the multimeter to the short-circuit detection gear to check whether there is a short-circuit phenomenon. If a short-circuit is found, it should be resolved immediately. The short-circuit phenomenon is also the most common failure of the LED display module. Some can be found by observing the IC pins and pin headers. The short circuit detection should be operated when the circuit is powered off to avoid damage to the multimeter. This method is the most commonly used method, simple and efficient.

(2) Resistance detection method
Adjust the multimeter to the resistance level, detect the ground resistance value of a certain point of a normal circuit board, and then detect the same point of another same circuit board to test whether the resistance value is different from the normal resistance value, if it is different, it is determined the scope of the problem.
(3) Voltage detection method
Adjust the multimeter to the voltage level, detect the ground voltage of a certain point of the circuit suspected of having a problem, and compare whether it is similar to the normal value, which can easily determine the scope of the problem.
(4) Pressure drop detection method
Adjust the multimeter to the diode voltage drop detection gear, because all ICs are composed of many basic units, but they are miniaturized, so when there is current passing through a certain pin of it, there will be a voltage on the pin.