Method of repairing sound 1. The stereo music is silent.
1. Insert a wired microphone into the M 1C (microphone) input port of the combined power amplifier, turn on the power supply of the power amplifier, turn the microphone front input control knob to the twelve o'clock position, and turn the microphone output volume knob to the twelve o'clock position. Turn on the microphone switch to make a phone call. If there is no sound in the microphone, insert the direct plug of the microphone into the other two microphone input ports in turn for testing. If all input ports are still silent after trying, the power amplifier may be faulty. You can contact the manufacturer's technical engineer by phone to consult the treatment method. If there is no electronic technical support, you should write down the fault state of the power amplifier on a small piece of paper and stick it on the power amplifier. After packaging, you should return to the factory for maintenance.
2. If the microphone has sound and the music is silent after the above method, first of all, check whether the input of the sound source (VOD) is correct, whether the input line is intact and whether it has been connected to the power amplifier reasonably. If the line is intact and connected correctly, but the music is still silent, you can check whether the selection of the music input port on the front panel of the power amplifier is consistent with the audio input port, and re-select the input port until there is music (if it is connected to the power amplifier after VOD output? CD？ Input terminal, and the front panel of the power amplifier has been selected? VOD？ Port, then the music must be silent).
3. If the music is still silent and the microphone can hear it after the above inspection operation, please check whether the VOD is faulty. You can move the amplifier to a room where both the music and the microphone have sound. If there is sound in other rooms, you can check whether there is something wrong with VOD (computer for ordering songs). If there is a problem with the setting or output of VOD, just reset and solve it.
4. If the audio adopts the combination of professional pre-stage and professional power amplifier, the inspection is roughly the same as the above method.
Second, the speaker sound is abnormal.
1, it is generally impossible for a speaker to burn out all high, medium and low units at once, so if the sound is silent, please check whether there is any problem with VOD, front stage and power amplifier first, and then check the speaker after confirmation.
2. Is the speaker issued? Bubu? Abnormal sound.
(1) Disassemble the box net, and check whether there is air leakage in the box and whether the unit is firmly installed on the box (sometimes the unit is not firmly installed, and in the process of high-power and dynamic use, the iron edge of the unit collides with the box, which will give off strange wind leakage). If all units are firmly installed, listen carefully to which unit the abnormal sound comes from.
(2) Take out the unit with abnormal sound, lay the unit flat on the ground, and check whether the bubble edge is broken and degummed, and whether the dust cap is degummed (usually? Bubu? The sound is related to the above reasons). If there is no degumming leakage, press down the unit naturally with the paper tray of the triangle scale with your right finger (there should be no noise when the normal unit is pressed down, but the unit will make abnormal noise caused by friction and voice coil deformation. )
(3) If the unit is not installed firmly and there is noise, it can be reinstalled firmly. If the unit has bubble edge or dust cap degumming air leakage, it can be sealed with agricultural machinery glue (glue for roadside shoe repair) and dried naturally.
(4) Check whether there is no foam rubber buffer strip at the contact point between the loudspeaker iron mesh and the box. If there is no foam rubber buffer strip, the noise can be eliminated by adding rubber strips.
⑤ If the horn unit is burnt out, it should be returned to the manufacturer for repair, because the voice coil and paper basin will affect the timbre. If the original voice coil and paper basin are not used, the timbre of the speaker will change.
Third, the speaker is inverted.
In actual use, the sound feels good after turning on one speaker, but after turning on two speakers at the same time, the sound becomes dry, and the low volume energy does not double, but the volume energy decreases or does not increase significantly. This phenomenon is due to the opposite phase of the speakers. It can be solved in the following ways.
1, check whether the speaker cable at the output end of the power amplifier is connected correctly (the positive electrode should be connected to the positive electrode, and the negative electrode should be connected to the negative electrode, which is generally extremely red. ), and then check whether the speaker cable is properly connected to the speaker port. If the system connection error leads to phase inversion, restore the correct connection.
2. If the speaker unit is installed upside down, remove the speaker and check whether the connecting cable of the bass unit is connected incorrectly. If so, just connect the two wires correctly. In addition, the battery can be used for polarity test. Touch the battery with the speaker cable to see the action direction of the speaker unit. After the positive and negative poles of the horn wire collide with the positive and negative poles of the battery, if the woofer moves outward, the phase is normal, and if the horn retracts, the opposite is true.
3. In addition, if the speaker is installed backwards, the simplest way is to reverse the positive and negative poles of the speaker line of a speaker at the output end of the power amplifier.
Car audio maintenance skills 1, a simple method to estimate DC working voltage
The maximum DC working voltage of cassette recorder can be estimated according to the number of batteries used in cassette recorder. If four No.5 batteries are selected, the working voltage is 4? 1.5v = 6v. This value is the same as the working voltage of the motor (except for motors and microcomputers with governors, the motor voltage is lower), and it is also the same as the DC working voltage of the audio power amplifier integrated circuit.
2. Check the printed circuit board copper foil connected to the socket.
When checking various sockets, pay attention to the copper wire connecting the socket pins. Because the socket is often used, when it is pulled out and inserted, the socket swings, which will break the copper foil wire connected with the socket pin or make the pin desoldering. Can I check with a magnifying glass or a multimeter R? 1? Document measurement.
3. Good habit of checking faults
When repairing the machine, we should rely on the electrical schematic diagram to establish the logical thinking of checking faults, rather than simply disassembling and replacing components, especially those suspicious faults, and rely on analyzing the working principle of the circuit to deal with them.
4, coarse and fine inspection problems
Check the fault first, and then check it carefully. If the fault can be handled directly, there is no need to stick to the routine system check. Only after the rough inspection fails can we enter the detailed system inspection, which is also divided into rough inspection and fine inspection.
5. Schematic diagram of inspection when there is no electricity.
Should we make full use of the sound without electrical schematic diagram? How to distinguish the audition function? And then what? Visual inspection? . When checking the circuit, make full use of the material manual to find a typical circuit as a basic reference circuit to find out the cause of the problem. Should be used as little as possible? Disturbance method? 、? Short circuit method? Wait a minute. In the absence of electrical schematic diagram, as long as we understand the working principle and structure of each unit circuit of audio, we can make good use of the material manual to check and troubleshoot.
6. Experience in distinguishing integrated circuits.
When the measured static working current value of the integrated circuit is greater than the given limit value of the material, it can be judged that the integrated circuit is damaged. If the static operating voltage of the output pin of the integrated circuit of the audio power amplifier violates half of the operating voltage VCC, the abnormal operation of the integrated circuit can be identified. When the working current of the measured integrated circuit is zero, the grounding condition and DC voltage of the integrated circuit can be checked first. If they are all normal, it can be judged that the integrated circuit is open.
Note: The premise is that the peripheral components are good.
7. The replacement process needs to be checked again.
During maintenance, if there is any doubt about a part, can I use it first? Current inspection method? When you find any doubt during inspection, don't rush to open it. At this time, you should use another inspection method to verify it, such as? Resistance test? . Because sometimes it's the first time to repair irritability? Current method? Misoperation or misunderstanding will occur during the inspection, and it is considered that the motor is in doubt. It took a lot of time to replace the motor, but the root of the problem was not found.
8. Check the ingenious use of the balance knob.
Flexible use of stereo balance potentiometer in maintenance can effectively distinguish defective parts. The balance control circuit is usually located before the left and right channel power amplifier circuit and after the preamplifier circuit. Listen to another channel by turning off the left channel or the right channel, and distinguish the fault parts according to the presence or absence of faults. This is the specific application of audition function distinction. When checking the circuit, it is usually necessary to distinguish whether the component is the left channel or the right channel. By adding disturbance to these components and changing the balance knob to change the speaker sound, it can be distinguished whether the left channel or the right channel is defective.
9, double card machine reference check
When repairing the movement of dual-card recorder, if the key can't be locked, the slider of the magnetic head of the movement can't be in place and the tension spring falls off. You can carefully remove the movement of another card and check the fault, which is the fundamental method of reference check. In a dual-card recorder, in most cases, the movements of the two cards are basically the same.
10, check the method of correcting the magnetic head lead.
In order to determine the mute problem caused by the open circuit of the recording and playback head lead, you can insert the spoon mirror for cleaning the head into the tape bin door (press? Play music? Key, let the head stretch forward), check with the help of a mirror. When the welding lead is disconnected, the front cover can be opened for welding. If you can only remove the tape recorder on the back cover, and it is very troublesome to remove it, you can try to weld it directly to the door of the warehouse. At this time, an improved electric soldering iron can be used. l？ ), directly into the welding. However, the operation should be very careful to avoid scalding the casing. If necessary, a heat-resistant cylinder can be placed in the door of the belt bin, and the welding head is welded from the cylinder, which is safer.
1 1. Requirements for measuring printed board resistance
When measuring the resistance directly on the printed board, after measuring with pointer multimeter, switch the red and black pens and measure again, and take the one with large resistance as the reference value (the dispute is definitely the accurate value); When measuring with a digital multimeter, it is enough to measure once. Of course, this is only the reference value of the measured resistance.
12, a simple method for measuring power transformer
A simple method can be used to measure the primary winding of power transformer: using multimeter R? 1? Measure the resistance between the two pins of the power cord plug; If the power input circuit is normal, the measured resistance is the DC resistance of the primary winding of the power transformer; If it is an open circuit, it cannot be judged that the primary winding is open, and it can only be judged by directly measuring the resistance between the outlet surfaces of the primary winding.
Audio maintenance methods pay attention to the storage environment.
The normal working temperature of audio frequency of power amplifier should be 18℃ ~ 45℃. Too low temperature will reduce the sensitivity of some machines (such as electron tube machines); If it is too high, it is easy to burn out the components or make the components age prematurely. Especially in summer, we should pay attention to cooling and keep the air circulating. It should be stored in a dry room, avoiding direct sunlight as much as possible, and never in a humid place to prevent the high-density machine-made board from expanding in the tide.
Remember to use it often.
Don't leave it unused for a long time. Use 1-3 times a month at least, and use 1 hour or more each time. Otherwise, it will bring a lot of troubles, such as static fatigue of materials, leakage of non-polar electrolytic capacitors in frequency divider, deformation of some parts and so on. , will affect the normal work and life.
Reset the function key every time you use it.
If the function key is not reset for a long time, its pull button spring will be in a stressed state for a long time, which is easy to cause dysfunction.
Matters needing attention when switching
Turn on the CD player from front to back, that is, turn on the CD player first, then turn on the front stage and the back stage. When turning on the power amplifier, set the volume potentiometer to the minimum. Turn off the power amplifier first and then turn it off, so that the amplification function of the power amplifier is completely turned off. At this point, when you turn off the front-end equipment again, no matter how big the surge current is, it will not affect the power amplifier and speakers. Similarly, when turning off the power amplifier, turn the volume potentiometer to the minimum, and then turn off the previous power amplifier and CD player after turning off the last power amplifier.
Close and reconnect.
Never turn on the power amplifier to connect the speaker cable, because the terminals of the speaker are generally very close, and the speaker cables are two closely parallel. When wiring, the speaker cable is often accidentally short-circuited, and the consequence is that the power amplifier will be burned out quickly. Although some power amplifiers are equipped with protection circuits, some HI-FI pure power amplifiers often omit this part of protection measures in order to improve the sound quality and reduce unnecessary sound pollution. So what? Turn it off and then connect? This sentence has long been a rule that enthusiasts must abide by.
About heat engine
Try to play some light music within half an hour after starting the machine, listen to the music at a moderate volume, and then turn up the volume to enjoy it after the machine is warmed up. Don't turn up the volume when the power amplifier is preheating, put on some explosive music. The reason is that the power amplifier module is in a cold state when it is just turned on, and its life will be shortened if it works with high current.
Regularly electrify
In the case of long-term non-use, especially in humid and high-temperature seasons, it is best to electrify for half an hour every day. In this way, the heat generated by the components in the machine can be used to drive away moisture, internal coils, speaker voice coils, transformers and so on. It can be prevented from being damaged by moisture.
Clean the contacts thoroughly every six months.
Soon after the metal is exposed to the air, the surface will be oxidized, lose its luster and become dull. Even though the surface of the signal wire plug is not easy to oxidize after gold plating, it is in close contact with the fuselage plug. But after a long time, there will still be a certain degree of oxidation leading to poor contact, so it will be cleaned once every six months at most. Use cotton dipped in alcohol to smear contact lenses. After such heavy work, the contact can be restored to the best contact, and the sound will be clearer and more transparent.
Cleaning the laser pickup of CD player
Obviously, the laser pickup has only a small area, but it depends on it to read the marks on the CD, so as long as there is a very small amount of dust attached to the pickup, it will affect the accuracy of reading signals. Although most CD players are sealed, don't forget that there is still a gap for dust to take advantage of in the process of frequent loading and unloading of CDs. After a period of time, there will be more or less dust on the surface of the pickup head.
At this time, it is necessary to unscrew the cover screw, open the cover and clean it directly with alcohol with a cotton swab. When cleaning a CD player that hasn't washed its hair for a long time, people will feel covered with gauze when listening to it again. The high frequency will restore the clarity of the past and the details will be much more beautiful. This step of cleaning the pickup head needs to be done once a year. Even if the pioneer reverse turntable system is used (the laser head is downward instead of upward), the dust will still be attracted by the static electricity carried by the pickup head and stick to it, so this time can't be saved.
Try to avoid overlapping machines.
Because of environmental problems, it is also helpless to stack the devices, but if possible, try to place the most important CD information source and the amplification part independently, because overlapping will lead to resonance and affect the machine. When the loudspeaker plays music, the vibrating air makes the equipment follow the vibration, and when the two machines overlap, it will spread harmonic vibration to each other, making the subtle information in the music vague, interfering with the transmission of each frequency band and producing a kind of sound pollution. For example, one of them is a CD player. When the motor rotates continuously, the amplitude of harmonic vibration intensifies and has a great influence. Therefore, the equipment should be independently placed on a stable rack.
The separated power supply keeps a certain distance from the main engine and the mono rear stage.
If the split power supply is far away from the front desk, if it is placed in another rack, the overall isolation can be improved in real time, and the audio and video will be more accurate. The same is true in the later stage of mono. Conditional two pieces of equipment are placed separately to ensure that they are beneficial and harmless.
Cancel the adjustable volume output of CD player
Many single CD players are equipped with an output that can adjust the volume, so that the volume can be controlled by the remote control. If you don't need this adjustable output, you can scrap it, or even scrap the earphone output device in front of the fuselage when you don't need it. The two sets of signal outputs are separated by the main signal. Once it is abolished, when only a set of fixed volume output is used, the energy of signal output does not need to be refined, the sound will be cleaner than before, and the sense of force will be better. It is not complicated to abolish these two sets of output modes, just open the cover and pull out the relevant connecting wires in the machine.
Reduce interference
Indoor household appliances and computers should avoid sharing a set of power with the stereo, and even if they are put together, they should get electricity from other places. Secondly, the entanglement of wires will also make the wires absorb noise from each other and destroy the sound quality. Whether it is the equipment or the connecting cable, it should be kept free from interference from other electrical appliances or power cords.
Horn setting
The placement of speakers is an important part in the use of audio, and poor placement will inevitably greatly reduce the playback effect. How to find the best placement in the room is quite a test of personal efforts. In addition to listening carefully to the effects of different placement positions, you can also ask relevant experts for guidance.
Dim environment contributes to listening effect.
It is a matter of habit to turn off the lights and listen to music. In a dark environment, the ears will be particularly sensitive, at the same time, the visual obstacles will be reduced, and the sense of sound picture reorganization and the position of musical instruments will be clearer. A good atmosphere is far from turning on the lights. Friends who don't like the dark environment can also use other dim lights to create a listening atmosphere.
sound-absorbing
In the general family environment, furniture and sundries are already excellent sound-absorbing materials, so there is no need to make sound-absorbing too complicated. Carpeting basically enhances the sound absorption effect. The advantage of adding carpet is that it can reduce the reflected sound of the floor and avoid mixing the sound from the front to cause turbidity. I want to know whether the room needs to be carpeted and whether the sound on the floor has changed.
When the horn is too close to the back wall, you can also consider adding tapestries to increase the sound absorption effect, but be careful not to use too large a piece, otherwise it may even absorb UHF.