Eight methods commonly used in electronic product maintenance (IV)

Disconnect circuit method:

When the circuit of the electronic product is short-circuited, the current flowing through the circuit will be large, and the power supply circuit and the short-circuited circuit are easily burnt out. In order to quickly find the faulty circuit, the disconnection circuit method can be used. If there are many circuits inside the electronic product, in order to judge which circuit has a short circuit fault, the circuit can be disconnected in turn. When a circuit is broken, the current of the power supply circuit suddenly becomes small, indicating that the circuit is a circuit with a short circuit. The circuit shown in the following figure is taken as an example to illustrate the use of the disconnected circuit method.

When the power supply resistor R is touched by hand, it is found to be very hot, which means that the current flowing through R is large, and there must be a short circuit in the three circuits. In order to determine which circuit is short-circuited, three circuits can be disconnected in turn (the previously disconnected circuit should be turned on and off when the next circuit is disconnected), when a circuit is broken, for example, when circuit 2 is disconnected. The temperature of the power supply resistor R decreases, indicating that the circuit 2 has a short circuit. Turn off the power, check each component in circuit 2 with the resistance method, and find the damaged components.