Examples of troubleshooting for radio and audio potentiometers

This article collects the solutions to the volume failure of some friends on the Internet and how to repair the potentiometer failure. If your baby has the following failure, you may also try to follow the instructions to try to see if you can fix it yourself.

A desktop computer SRS sound controller has been used for more than ten years. The volume potentiometer is seriously in bad contact, the full scale is noisy, and it cannot be positioned, and it is fleeting. Because there is no electrical lubricant on hand, it has to be replaced with anhydrous alcohol Clean and lubricated, not only does not work well, it can only be maintained for about a week. Repeated disassembly and assembly many times, unbearable.

The standard cleaning procedure of the potentiometer should be: first solder the potentiometer from the circuit board, open the shell, clean the carbon diaphragm with a cotton swab dipped in absolute alcohol, and then apply a little lubricating oil. If the carbon diaphragm is severely damaged, you should use the camera to move the contact to make it slide on a new track, and then repeat the above steps. This is very easy for large desktop radios or large potentiometers on old tube radios. If the lead wire is long enough, you don’t even need to use an electric soldering iron. Just pull the pin of the dust cover and remove it to see Inner core. Similarly, the small potentiometer on the portable semiconductor radio is easier, as long as you open the back cover, remove the knob and the dust-proof sheet, you can operate it. But now most potentiometers are directly soldered on the circuit board, and most of them are dual-connected shafts with 6 pins, which is quite troublesome to disassemble. If it is not done, it will damage the printed circuit pads and cause other failures. Big.

Later, with the mentality of a dead horse being a living horse doctor, I found a bottle of ordinary machine lubricant, followed the gap of the lead hole, and poured it in with a syringe until the bottom of the potentiometer leaked out, while turning the knob from time to time to make it even. Absorb oil.

1. The sound can be played normally, but there will be a "peep bang" noise from time to time.

Customers report that there is no other noise when the computer is using the headset, but it will make a "pop" noise from time to time when using the speakers. Sometimes the time is longer, sometimes the time is shorter, and then it is normal. At the beginning, I suspected that the audio signal plug was not in good contact, but it was re-plugged and the problem was not solved after changing the cable. However, after the customer took the speaker to the company, he tried it for two consecutive days, but no problem was found. Comparing the difference before and after, only the socket is different. At this time, I also remembered that the power socket on my desk, because of its poor quality and insecure contact, would be strong for a while and weak for a while, causing the desk lamp to light up for a while and darken for a while. It seems that the problem reported by the customer is true, and the reason is that the quality of the power socket is poor, the quality of the phosphor copper sheet used internally is not good, and the flexibility is poor. After a long time of use, the contact is not good. After contacting for a while, the power of the speaker is turned on and off for a while. Because there is a large-capacity filter capacitor inside the power supply, the power supply voltage of the power amplifier circuit will be high and low, and the sound strength will change significantly; at the same time, because there will be interference signals of current on and off at the moment of on and off Into the amplifier circuit, it will also cause other noise.

Solution: Replace with a new high-quality power socket. Some profiteers may take advantage of reasons that customers don’t understand, to demonstrate to customers that the speakers have been repaired, and to collect money.

2. The sound can be played normally, but if you adjust the bass (BASS), the loudspeaker will emit a "crack" noise, which is simply unbearable.

Sometimes some speakers will have a "crack" noise when in use, especially when the subwoofer knob is turned, the situation will be more serious. Because it is caused by rotating the BASS knob, it is certain that the BASS potentiometer is damaged. The volume adjustment and subwoofer adjustment of most speakers use potentiometers to change the strength of the signal, except for the new digital tuning potentiometer. The potentiometer changes the resistance value by changing its position on the carbon resistor through a movable contact. As the use time increases, dust or impurities will fall into the potentiometer, and the contacts of the potentiometer may also be oxidized and rusted, resulting in inaccurate contact. At this time, there will be a "crack" when adjusting the volume. The noise appears. It is simple to deal with this kind of problem, just replace a new potentiometer, and the cost will not exceed 2 yuan. However, the simplest solution is to open the case, open the four crimping tabs behind the potentiometer, and clean the carbon baffle with absolute alcohol on the movable contact of the bottom potentiometer, and then drop a drop of oil on the carbon baffle. , Install the potentiometer in the original position to solve the noise problem. However, the reason for this example is because the quality of the potentiometer is unstable. When in use, the reeds of the left and right channels were originally separated, but now because of the misalignment, they are turned on and off during use, which results in a "thunderbolt". "Para" noise. We only need to use needle-nose tweezers to gently pull it up, and then press the original position to reinstall it. If there is a similar noise when adjusting the volume, it can also be repaired in this way.

3. The sound is played normally, but one speaker has a loud sound, and the other has a small sound. If you push the volume potentiometer to one side with your hand, the volume of the two channels will be the same.

This case is similar to the second type of failure, which is also a problem with the volume potentiometer. Because the volume potentiometer left and right channels are independent. Because the reed has been used for too long, the elasticity of the inner reed is too weak to be in close contact with the carbon barrier. Finally, connect the common ground terminal of the potentiometer directly to eliminate the fault.

4. Turn on the power switch of the speaker. When the speaker is not turned on normally, there will be a "bang" sound when the speaker is turned on. Turn on the MP3 player and adjust the volume. There is no sound from the speakers.

This kind of failure is common, and there is no sound from the speaker after turning on. How can we tell if the speaker is really broken? First, before powering on the speaker, turn the volume level to the maximum position. When turning on the power switch, pay attention to whether the speaker makes a "pop" sound. If there is, it means that there is no problem with the speaker, the power supply is good, and no sound may be caused by a sound card driver error or sound failure, or it may be muted or the volume is too low, and the signal cable plug is not properly connected. Or the signal wire is broken. Also, if we touch the plug of the signal cable to the metal part of the chassis, the speaker will emit a "humming" hum, which is particularly obvious.

However, this case is because the speaker has been used for too long and the internal temperature is too high, causing the temperature fuse in the power transformer in the speaker to fuse. Don't worry, we don't need to replace the power transformer, just remove the transformer carefully, and observe the primary coil of the power transformer (that is, the end connected to 220V) from the outside, and see which side is protruding a little. On the convex side, use sharp tweezers to carefully disassemble the plastic film on the surface, and you will find a small white square with the words "250V2A" written on it. This is the temperature safety resistor. Because the use time is too long and the temperature of the transformer is too high, in order to avoid fire, the fuse resistor operates to cut off the current supply. We only need to short-circuit both ends of the fuse resistor directly, but in the future use, we need to pay attention to heat dissipation and do not use it for too long.

Many computer peripherals that use power transformers, such as the external power supply used by CANON and HP inkjet printers, the power adapter used by the external modem, the external power supply used by some speakers, the 220V/9V or 12V transformer in the box, and the coil inside All are equipped with temperature insurance resistors. Especially the power transformers of CANON and HP printers are difficult to match, and the repair fee is very high. However, the actual repair is to disassemble the transformer and short-circuit the fuse according to the above method.

5. There is sound, but only treble, but no bass.

This kind of malfunction is usually caused by the loud speaker volume, long time use, burning the subwoofer we usually talk about, or it may be a broken wire. It only needs to spend more than ten dollars to replace a new one.

6. There is sound, but the sound is not clear, and the specific content cannot be heard clearly.

In addition to damage to the tweeter, this failure may also be a broken signal line or a damaged integrated block for the tweeter amplification.

Note: If you are using a soft sound card, sometimes you may inadvertently change the settings, so that the speaker can only be heard clearly, but the male voice cannot be heard clearly.

7. As soon as it is turned on, it will "buzz" directly, no matter how the volume is adjusted, the noise cannot be eliminated.

This situation is generally due to long-term use, and the speaker is closed, the heat cannot be dissipated, the internal temperature is too high, and the integrated block is overheated and damaged. In fact, all genuine power amplifier integrated circuits have a temperature protection function. When it is overheated, the power amplifier integrated circuit will automatically stop output. When the temperature drops, it can automatically resume work. However, in order to reduce production costs, some speaker manufacturers use integrated circuits that are not brand-named by large manufacturers, but use integrated circuits that are imitated by small manufacturers, which are of poor quality. The solution is to buy an integrated circuit of the same model to replace it, and the cost is only 5 yuan.

8. When the computer is turned on, the sound played by the computer is normal, but after using it for a period of time, it "buzzes" and the ears can't bear it.

This example of failure is the same as the previous example, but the power amplifier integrated circuit has not been completely damaged, and the failure occurs when it is overheated. We can open the case and increase the area of the loose chip of the power amplifier integrated circuit, or replace the good quality chip.