Car audio maintenance method 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.
The brand of luxury car is not necessarily good.
Most people don't know much about audio, so the way most people judge whether it's good or not is that Mercedes-Benz BMW is good and ordinary brands are bad. In addition to the price gap, the powerful publicity ability of luxury brands also makes consumers admire the audio brands they promote. For example, the Voice of Berlin was ignored several years ago. Since Mercedes-Benz began to promote vigorously, it has become a household name immediately.
In fact, audio and automobile are two completely unrelated technical fields, and there is still a big gap between the brand promoted by automobile manufacturers and the brand value in the professional audio field. For example, BOSE, which is loved by many high-end manufacturers, is actually about the level of Nike Adi in the field of professional audio, but it is also very happy to be chosen by automobile manufacturers because of its popularity among ordinary consumers. BOSE mainly sells home theater or headphones, computer speakers and other products, and the most expensive home theater system sold in China is about 50 thousand yuan.
Another example is the recently popular focus sound used in the newly listed Peugeot 5008. If it is not adopted in 5008, I am afraid that few people have heard of it. But in fact, FOCAL is indeed the top brand of fever audio, and its Utopia series is even more famous among professional audio players. It's not a problem that a sound system can easily sell for hundreds of thousands, and the price of top-class Jin Lang audio will even exceed one million dollars. So from the brand level, Jinlang and BOSE are completely different. So if you want to know the real gold content of a car audio brand, the easiest way is to check the price of its products in the traditional audio field.
The gap between products of the same brand can be exaggerated.
Is it enough to choose the right brand? It's not that simple. The impression gap between different models of the same brand has also been exaggerated. For example, they are all BOSE brands. The Cadillac CT6 is equipped with 34 top-mounted system speakers, and even speakers are arranged on the backrest of the seat, which is far better than the BOSE used in most models. Another example is the widely promoted Voice of Berlin by Mercedes-Benz. It is equipped from C to S, but the price of optional equipment alone is about 1 10,000 yuan for the Voice of Berlin system for C, and the price of the top-mounted Voice of Berlin for S will reach 6.5438+10,000 yuan. Aside from the premium rate of the model itself, the gap in products is also very large. Therefore, when we compare the sound system, we should not only look at the brand, but also look at the number, layout, power and other information of speakers.
Big names don't mean skills.
Most high-end audio brands have their patented technologies and distinctive highlights, but these patented technologies are not necessarily applicable to car audio. For example, Dana started as a speaker at first, and the biggest feature of the self-produced speaker products later was the use of a large voice coil, but the large voice coil needed a high-power and high-quality amplifier to promote it, which was difficult to achieve in car audio, and Dana could not arrange speakers in the car, so the car-mounted Dana system could not convey all the characteristics of Dana audio.
Back to the FOCAL mentioned above, it really started with a speaker. It provides speaker units for more than 50 audio manufacturers. W? One of the characteristics of the vibrating basin is that it is light to push, which is very suitable for car audio.
No matter how many audio brands there are, there is actually only one name left. For example, the well-known Harman Group owns many audio brands such as Mark levinson and Harman Kardon, while Mark levinson used by Lexus is a brand famous for its power amplifier. As the exclusive audio of Lexus, it is more about distinguishing brands, so if you remove a speaker like Harman Kardon from the door of Lexus, you don't have to panic at all. Therefore, for players who are more interested in studying, you should know what the characteristics behind the audio brand are, whether it is suitable for you, and whether it can be reflected in the car.
Method for judging the quality of audio host 1. Output power: At present, the power of the host computer is mostly music power, ranging from 40W to 60W, and the power should not be too large.
2. Frequency response: The frequency range that the human ear can hear is between 20 Hz and 20 kHz, so the index should at least reach this value, and the wider the better.
3. Signal-to-noise ratio: refers to the ratio of music signal to noise. Generally, high-end car stereos are above 90DB, and the larger the value, the better.
4. Harmonic Distortion (THD): This indicator reflects the reduction of sound reproduction. The smaller the value, the higher the degree of restoration and the better the sound effect.
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