First, set the multimeter at the resistance X 1 to see if the four diodes of a rectifier bridge are in good condition, and then measure the resistance of the motor inside the rectifier bridge to see if the motor is in good condition. Then measure whether the resistance is normal and whether the switch is in good condition.

2. Next, turn on the power. Find the live wire and the zero wire before electrifying, and find out which incoming wire is connected to the live wire and which incoming wire is connected to the zero wire. Then, the multimeter hits the AC voltage range, and the black pen is connected to the zero line plug to ensure that the zero line is normal. Then use a red pen to measure from the incoming line, switch, resistance and motor, so as to see where the voltage disappears, and the fault appears in front of the voltage disappearance point.

Extended data

The motor of the blower is a DC permanent magnet motor.

Permanent magnet DC motor is also composed of stator pole, rotor, brush, outer

Schematic diagram of motor structure

Shell and so on. The stator poles are made of permanent magnets (permanent magnet steel) made of ferrite, Al-Ni-Co, NdFeB and other materials. According to its structural form, it can be divided into cylinder type and tile type. Most of the electric motors used in tape recorders are cylindrical magnets, while most of the motors used in electric tools and automobile appliances are special block magnets.

The rotor is generally made of silicon steel sheets laminated, which has fewer slots than the rotor of electromagnetic DC motor. Most of the low-power motors used in tape recorders have three slots, and the high-end ones have five slots or seven slots. The enameled wire is wound between two slots of the rotor core (three slots have three windings), and its joints are welded on the metal sheet of the commutator respectively. Brush is a conductive component connecting power supply and rotor winding, which has both conductive and wear-resistant properties. The brush of permanent magnet motor adopts neutral metal sheet or metal graphite brush and electrochemical graphite brush.

The permanent magnet DC motor used in the recorder adopts electronic speed stabilizing circuit or centrifugal speed stabilizing device.

Reference materials? Baidu electric encyclopedia