1. Resistance detection method, adjust the multimeter to the resistance gear, detect the resistance value of a certain point of a normal circuit board to ground, and then test the same point of another same circuit board to test whether the resistance value is different from the normal resistance value, If not, the scope of the problem is determined.

2. 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, otherwise the scope of the problem is determined.

3. Short-circuit detection method, adjust the multimeter to the short-circuit detection gear (some are diode voltage drop gears or resistance gears, generally with an alarm function), detect whether there is a short-circuit phenomenon, and solve it first after finding a short-circuit, so that it does not burn out other devices. The method must be operated with the circuit de-energized to avoid damage to the meter.

4. The voltage drop detection method, adjust the multimeter to the diode voltage drop detection gear, because all ICs are composed of many basic single components, but they are miniaturized, so when there is current passing through one of its pins, There will be a voltage drop across the pin. Generally, the voltage drop on the same pin of the same type of IC is similar. According to the value of the voltage drop on the pin, the operation must be performed when the circuit is powered off. This method has certain limitations. For example, if the detected device is high resistance, it cannot be detected.