Carbon film potentiometer failure and detection method2021

Carbon film potentiometers sometimes have some failures during use. Today we will list several failures of carbon film potentiometers, and analyze the causes of the failures, and tell you some solutions to potentiometer failures, and carbon film The detection method of the potentiometer.

Several common carbon film potentiometer failures and their causes

1. The carbon film potentiometer has a large rotating noise: it mainly appears in the volume potentiometer, because the volume potentiometer often rotates.

2. The carbon film potentiometer is seriously burnt out due to overcurrent: At this time, the carbon film potentiometer burns into an open circuit. When the volume is adjusted, there will be "creaking" and "creaking" sounds in the speaker, and the noise will disappear when the carbon film potentiometer stops rotating. This indicates that the volume potentiometer has a problem with large rotating noise.

3. Open circuit failure of the internal pins of the carbon film potentiometer: At this time, the circuit where the volume potentiometer is located cannot work normally. For the carbon film potentiometer, there may be a silent fault or the volume cannot be turned off.

Solution to the failure of carbon film potentiometer

The biggest fault of the carbon film potentiometer is the large rotating noise, which can be repaired by cleaning. The specific method is: folding method to let the pure alcohol cleaning liquid flow to the carbon film inside the potentiometer. Slide on the carbon film to achieve the purpose of cleaning the carbon film and contacts. This cleaning can be done with electricity. It should be noted here that pure alcohol must be used. Then turn the handle to listen to the size of the noise, and guide the noise until it disappears. How to make the cleaning liquid flow onto the carbon film?

1. For the straight-slide carbon film potentiometer: it should be dripped from the gap of the handle.

2. For carbon film potentiometers that cannot flow in from the outside: you can open the shell of the potential before cleaning.

3. For potentiometers with large gaps at the pins: naturally drip in from the gaps in the pins.

4. For potentiometers with large gaps in the handle: you can drop in from the gap in the handle.

Detection method of carbon film potentiometer

1. The resistance measurement method of the carbon film potentiometer: The resistance measurement of the carbon film potentiometer is divided into in-circuit measurement and off-line measurement. Since the pins of the general potentiometers are connected to the circuit on the circuit board with leads, it is more convenient to weld the leads, and the faults are measured by disconnection, so that the measurement results can accurately explain the problem.

1. Measure the resistance between two fixed pins. Its resistance value should be equal to the nominal resistance value on the potentiometer housing, much larger or much smaller than the nominal resistance value indicates that the carbon film potentiometer has a problem.

2. Detect the change of resistance value. Use the multimeter with the corresponding range in the ohm range, one meter rod with the moving piece, the other meter rod with the fixed piece, slowly rotate the handle of the carbon film potentiometer left and right, the resistance value indicated by the pointer should be from zero to the maximum, and then from the maximum The value changes continuously to zero. The pointer deflection should also be continuous, that is, there should be no pointer jump.

2. Audition detection method of carbon film potentiometer: This method is mainly used for noise fault detection of volume potentiometer and tone potentiometer. Let the circuit be in working condition, and then rotate the carbon film potentiometer handle left and right to let the movable piece contact slide on the carbon film. If there is a "creaking" or "creaking" sound in the speaker during rotation, the carbon film potentiometer has a large rotating noise failure. On the contrary, if there is no noise, the carbon film potentiometer is basically good.

Generally, volume potentiometers or tone potentiometers are used for a period of time, and there will be more or less rotating noise failures after seeing them. If this is due to the friction between the carbon films of the rotor contacts, the carbon film will be damaged and the rotor will be damaged. Poor contact with carbon film.

After the carbon film potentiometer is cleaned, the noise will completely disappear. At this time, in order to reduce the friction, it is best to put a drop of lubricating oil on the carbon film, which can also increase the service life of the potentiometer. In addition to the above methods, the precautions for using carbon film potentiometers must also be known.