Imported electric screwdriver repair method

First, the repair tool

Two multimeters (one for each of the analog and digital figures, the analog type is indispensable), a diagonal pliers, a needle-nosed pliers, a soldering iron, and a soldering iron stand. Flux, tin wire, suction tin, fine sandpaper, heat shrinkable sleeve, wire stripper, slotted screwdriver (one for each small and medium), Phillips screwdriver (one for each small and medium, plus a rubber handle screwdriver), art Knife.

Second, the working principle of the circuit

1, the process

Input (protector, micro switch) → rectification → filtering → positive and negative switch → motor → clutch

2. Normal parameters of each electronic component

(1), power line: measure DC resistance value, the normal value is close to zero; common fault: open circuit or poor contact (break).

(2), micro switch: measure the resistance between normally open (resistance is close to infinity) and normally closed (resistance is close to zero); common fault: bad contact contact (burning black), the button can not be reset normally, the body rupture.

(3), protector: measure the resistance value; normal zero; after a slight overload, it can be automatically reset, when it is too large, it will be permanently disabled. It can also be disconnected (thermal protector) in case of high temperature, and can be automatically reset after normal temperature.

(4), rectifier bridge: short-circuit the output (+, -), test the output (+, -) DC resistance (about 15K).

(5) Positive and negative switch: The pin corresponding to the toggle button is a common pin, and the two gears corresponding to the toggle button are connected.

Third, circuit detection and analysis

When you get an electric batch with unknown cause of fault, you should make a preliminary test, as follows:

Turn the multimeter to (×1K) to zero, open (press) the micro switch, and measure the DC resistance of the input, which is about 15K under normal conditions (the digital multimeter is adjusted to the diode, showing a voltage drop of 1. 0 Left and right), this value can explain that the electric batch circuit works normally. The other method of detecting the circuit is to short the motor after opening the electric batch. Under normal conditions, the DC resistance value of the input terminal is slightly smaller than the initial measurement. The maximum value (motor DC resistance value is not included in the calculation).

Fourth, the components of the motor

1. Basic components: armature (rotor), carbon brush holder, motor front cover, bearing, magnet (stator), carbon brush, motor gasket.

(1), armature: the most important parts of the electric batch, just like the "heart", the state of the armature will determine whether the electric batch can work normally. The quality of the armature: we can know by measuring its DC resistance. Under normal conditions, the DC resistance (220V) between the adjacent poles of the armature commutator is about 15 ohms (the value is different due to the manufacturer, and the larger DC resistance exceeds 20 ohms).

Damage characteristics and failure analysis: A, judging from the appearance of the armature's commutator with obvious wear, the armor with more serious wear is very noisy when working: B see if the central axis of the armature becomes smaller (fit the bearing Later, when the bearing can sway from side to side, the center of rotation of the armature is unstable and the noise is large. C, there are many armatures that cannot work properly due to the open circuit of the two adjacent poles of the commutator. When there are multiple disconnections, the motor cannot be started; when there is a disconnect, the motor can work, but if the carbon brush is in contact with the disconnect, the motor will stop working.

(2) Carbon brush holder: It is judged from the appearance that it is damaged or internalized (blackened).

(3) Motor front cover: It is judged to be damaged from the appearance.

(4) Stator: It is judged from the appearance whether the internal disk is damaged or displaced (causing magnetic asymmetry), and a word screwdriver can be placed inside the magnet to check the magnetic size. When the magnetic force is too small, it should be replaced. New magnet.

(5) Bearing: It is judged from the rotation bearing that there is a stuck phenomenon, and when the internal friction is strong, the motor is crying loudly.

(6) Carbon brush: When the carbon brush is worn to the remaining two or three millimeters, replace the new carbon brush (replace regularly).

(7), gasket: fixed armature to prevent up and down shaking, to ensure smoothness. The appropriate number of shims; the armature will not sway up and down, and the armature can be twisted with less force.

Five, clutch

1, the common fault of the clutch: (1). Unable to catch the screwdriver head: A drive shaft is broken, replace the drive shaft (slot becomes large, automatically falls off); (2). Missing, make up new.

2. The drive shaft is damaged: (1). The appearance of the screwdriver head is severely worn and needs to be replaced; (2). Internal break (test method is to put the fan into the clutch, then snap it, use a screwdriver to twist the drive shaft to judge the sense of jump, and determine its good or bad.)

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