Analysis and treatment of common failure cases of desktop centrifuge

Example 1. The motor speed becomes slower and the brush emits a large spark

Analysis and maintenance: This fault is caused by dirt between the carbon brush of the motor and the commutator or the spring force of the carbon brush spring is reduced, resulting in poor contact between the carbon brush and the commutator. Disassemble the machine, unscrew the brush box cover, and take out the carbon brush with spring. First clean the dirt on the spring, carbon brush and commutator with absolute alcohol. If the front end of the carbon brush is chipped, use assorted files and sandpaper to grind the carbon brush into a smooth curved contact surface to make it round. The reversal film agrees well. Then increase the spring force appropriately. After the above processing, the fault can generally be eliminated.

Example 2. When the tabletop centrifuge is working, it makes a loud vibration noise

Analysis and maintenance: The reasons and solutions for the vibration and noise caused by the centrifuge are:

(1) The mechanical parts and fasteners such as the fixed turntable screw on the upper end of the rotating shaft or the damping spring fixing screw on the machine base are loose, as long as they are tightened again.

(2) The motor shaft is bent or the bearing is worn. If the motor shaft is bent, it can be solved by repairing and correcting, and it should be replaced when it is serious; if the bearing wears, the gap increases, it can be solved by a gasket on the bearing. If it is serious, it should be replaced.

(3) The elasticity of the three shock-absorbing springs on the frame becomes small or broken, which makes the turntable shake more when it rotates. Just replace the shock absorber spring.

(4) The outer cover is deformed or the position is incorrect. As long as the outer cover is repaired, adjusted and corrected, and the outer cover is installed and fixed firmly, it can be solved.

(5) There are foreign objects such as broken glass in the test tube sleeve, which makes the load unbalanced. Before each use, check whether there are other foreign objects in each casing. If there are any foreign objects, they must be removed before use.

(6) The test tube set does not match the machine. The test tube cover is specially matched for the machine by the manufacturer. The test tube sets of different types of centrifuges cannot be exchanged at will. Otherwise, vibration noise will be generated when the centrifuge is working.

Example 3. When the power is turned on, the motor does not rotate

Analysis and overhaul: During overhaul, first observe whether the work indicator light is on. If it is not lit, the cause of the failure is generally the open circuit of the power transformer BI primary coil except for the defective input circuit of the power cord and power switch K1. If the BI is a non-burnt open circuit, you can use a multimeter to measure the opening and closing of each tap in turn to find the open circuit (open circuit point), as long as the open circuit point is re-welded. If the BI is a burn-out circuit, it must be rewound or replaced. If the indicator light is on, you should check whether the speed switch K2, timer and motor are damaged in sequence. First measure whether there is 220V voltage at both ends of the motor; if not, the timer and K2 are disconnected. For the inspection of K2, a knife can be used to scrape off the oxide on the contact surface. Then adjust the initial position of the correction contact shrapnel to make good contact. For the inspection of the timer, the timer can be removed and disassembled, and its contacts can be cleaned, adjusted and corrected. If the mainspring or cam is damaged, the timer should be replaced; if there is 220V voltage at both ends of the motor, then The motor is defective. Listen to the motor for "buzzing" sound. If yes, the motor stator and rotor are stuck by foreign objects. Just disassemble the motor and remove the foreign objects between the rotor and stator. If there is no "buzzing" sound, it is The winding is broken, you can rewind or replace it with a new motor.

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