DIY car audio amplifier repair. Car amplifier repair

It's no secret that you need a power amplifier to get high-quality sound and powerful bass in your car. Today, fortunately, on the market you can find car amplifiers for every taste, it all depends on your specific needs. An amplifier for 200-400 watts is enough to power the standard car acoustics, but among us there are true connoisseurs of sound pressure, audiophiles and music lovers who cannot be surprised by a couple of hundred watts of sound power.

It is for such people that class D amplifiers were invented - digital audio amplifiers that have high efficiency, compact dimensions and many other advantages.

Unfortunately, the car amplifier sometimes breaks down, in some cases the repair is more expensive than the initial cost of the amplifier itself, so it is very desirable to consider or try to repair it yourself, because sometimes a blown fuse can be the cause of the breakdown. Having at hand a simple and cheap multimeter with diode continuity mode, you can find most of the defects that are very often observed in many car amplifiers.

Any car amplifier consists of three main parts - a voltage converter, a power amplifier block and a filter block (crossover).

A voltage converter or inverter is the most vulnerable part in any amplifier - 90% of the problems are associated with this particular node. The converter essentially powers the entire amplifier including the filter bank.

Exclusively all voltage converters are made according to the standard push-pull circuit using a PWM controller, most often on the TL494. Then everything is standard - driver, power transistors, transformer, rectifier and filter unit. In some (cheap) amplifiers, unregulated inverter circuits are implemented - in a word, there is no control of the output voltage, of course this is rather bad, but it is not at all a necessary process if the amplifier is not sensitive to the supply voltage and is a cheap model.

Converter transistors - they are the ones that fail most often. In cheap Chinese amplifiers, transistors are strangely marked, even if you cannot find similar transistors, you just need to know one thing - the keys can always be replaced with IRFZ40 / IRFZ44 / IRFZ46 / IRFZ48 or more powerful IRF3205, the choice of keys is actually quite large, I just listed the most available options. In general, N-channel field-effect transistors of high power are used exclusively in all inverters of automobile low-power transistors - up to the brutal IRF1404.

Initially, we check the board by eye - sometimes visible defects can be observed (burned out resistor, broken tracks on the back of the board, etc.)

Before replacing the transistors, you must first check the power fuse, the diode on the plus and minus buses (when the power is reversed, it also burns out), and only after you have made sure that everything is ok with these parts, we replace the keys.

For more professional repairs, an oscilloscope is indispensable. Initially, you need to check for the presence of rectangular pulses at the 9th and 10th output of the generator microcircuit, if any, then the microcircuit is working. Then we check for the presence of the same pulses after the driver - on the gates of the field switches. If there are no pulses, then most likely the problem is in the driver, if they are, then we do not hesitate to replace the field-effect transistors.

It is extremely rare that there is a problem with the power amplifier, the converter burns out first, keeping the amplifiers. In the converter, other breakdowns are possible, although very rarely. There is a problem with the input and output capacitors or the diode rectifier that rectifies the high frequency AC voltage from the transformer.

A low frequency amplifier (ULF) is a device every music lover knows about the purpose of. This component of the audio system improves the overall sound quality of the acoustics. But like any other electronic device, AU can fail. For more information on how to repair amplifiers of car audio systems with your own hands, learn from this article.

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Typical malfunctions

Before you repair, install and configure the ULF in your car, you need to understand the breakdown. It is simply impossible to consider all the faults that can be encountered in practice, since there are a lot of them. The main task of repairing a device for sound amplification is considered to be the restoration of a broken component, the breakdown of which led to the inoperability of the entire board.

In any electrical engineering, including amplifiers, there can be two types of faults:

• contact is present where it should not be;
• in the place where the contact should be, it is absent.

Functional check

The repair of car amplifiers first of all begins with the diagnosis of ULF:

1. First you need to open the case and carefully examine the circuit, use a magnifying glass if necessary. During diagnostics, you can see the destroyed components of the circuit: resistors, capacitors, broken conductors or burned-out paths of the board. But if you find a burned-out component, you need to take into account that its failure may be the result of the burnout of another element, which in appearance may seem whole.
2. Next, diagnose the power supply, in particular, check the output voltage. If burnt resistors are identified, these elements will need to be changed.
3. Apply power to the ULF and the Remout output, then you need to close the system to plus and look at the PROTECTION diode indicator. If the light comes on, this indicates that the device has gone into protection. The reason may be poor power supply or its absence on the board, breakdown of the transistor, or problems in the operation of the voltage converter. In some cases, the reason lies in the breakdown of a transistor power amplifier for one of several channels.
4. If after the power was applied, the safety element did not burn out, you need to check the voltage level at the output. It should be approximately 2x20 in or more.
5. Carefully inspect the transformer device of the voltage converter; it may have burnt-out turns or open circuits. Smell this element, maybe it smells burnt. In some ULF models, a diode assembly is installed between the PN output and the amplifier - if it fails, the unit can also turn on protection.

Elimination of breakdowns

Do-it-yourself car amplifier repair is carried out in accordance with what problem was identified during its operation:

1. If the transistor in the car amplifier breaks down, then before directly replacing it, it is recommended to diagnose the safety element by the power supply. You also need to make sure that the diodes on the buses are working. If everything is in order with these parts, the installed transistors must be replaced.
2. For more specialized repairs, you need an oscilloscope. Having installed the probes of the device on pins 9 and 10 of the generator board, you need to make sure there are signals. If there are no signals, then the driver changes, if they are, then the field-effect transistor elements are replaced.
3. Capacitors change much less often during the repair process - as practice shows, this does not happen often (the author of the video is the HamRadio Tag channel).

Basic aspects of amplifier tuning

Now let's move on to the question - how to set up a car amplifier? There are several configuration options - for use with and without a sub.

How to properly configure the ULF without a subwoofer - first you need to set the following parameters:

• bass boost - 0 decibels;
• level - 0 (8V);
• the crossover must be set to FLAT.

After that, adjusting the settings of the audio system with an equalizer, the system is configured to suit your preferences. The volume must be set to maximum and include some track. How to set up for use with a subwoofer is also not particularly difficult.

For correct configuration, it is advisable to use the following parameters:

• Bass Boost should also be set to 0 decibels;
• the level is set to 0;
• the front crossover is set to the HP position, and the FI PASS control element must be set in the range from 50 to 80 Hertz
• the rear crossover is set to LP and the Low control must be set between 60 and 100 Hertz.

It is very important to observe these parameters, since they determine the quality of adjustment and, accordingly, the sound of the audio system. In general, the setup procedure is similar, using the level control to provide a more harmonious sound. The sensitivity of the rear and front speakers should be matched to each other.

If you do not understand anything about this, it is better not to go there, because repairs will cost more after you still burn or break.

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Do-it-yourself sound amplifier repair nowadays, more and more users of audio equipment are producing who have at least a little skills in electronics, prefer to repair their sound amplifier with their own hands

Everyone is well aware that modern and not expensive audio equipment is mainly produced in China and of course it cannot be compared with Hi-Fi equipment, not only in terms of the parameters declared by the manufacturer, but also in terms of build quality, reliability in operation, and sound quality and of course the lack of technological capabilities for a normal repair. Therefore, the majority of natural sound lovers independently maintain in working order both Soviet-era equipment and used imported equipment. Especially a lot of recently, in view of their low cost, imported power amplifiers in disrepair are supplied to our markets. p\u003e

This article will describe purely practical advice that I use in the repair process. Therefore, if you have certain skills and desire, you can do it yourself to repair the sound amplifier at home. Most breakdowns in amplifiers or similar devices are indicated by a lack of input signal, or when the mains voltage is turned on, the high-voltage fuse or DC fuses immediately blows. In this case, the malfunction is most likely in the output stage of the device assembled on transistors or in a hybrid circuit using integrated circuits. If the mains fuse burns out when turned on, then there is a high probability that the power supply is faulty or a short circuit in the high-voltage circuit, there may simply be a banal short circuit in the mains plug or wire. Still start doing audio amplifier repair should be in this order: before proceeding with the direct search for a malfunction, you need to conduct a visual inspection of all nodes, modules and electronic components for the presence of darkened or clearly burnt elements and wires, and when inspecting electrolytic capacitors for the presence or absence of electrolyte leaks, or swelling of containers.

After a thorough visual inspection, you can start doing it yourself repair of a sound amplifier on your ownhaving prepared the necessary tools and measuring devices in advance. I always start troubleshooting from the terminal path of the amplifier, and only after determining the inoperative stage, I need to look for the problematic part there. When the power supply of the device is turned on and the input signal is applied to the input circuit, while without using measuring instruments, you need to touch the surface of the case of powerful transistors or microcircuits installed on the cooling radiators with a dry finger of your hand, thereby determining the approximate temperature of the element. If no heat is felt on the output keys, this means that there is no current in the circuit, which, in fact, should have heated the transistors or the microcircuit. And if, on the contrary, it is impossible to keep the finger on the surface of the transistor, then this also means a malfunction in this amplifier stage. In the same way, you need to check other electronic components, namely parametric voltage stabilizers and electrolytic capacitors, in case of leakage or swelling of capacities, they must be replaced, this is true for all electrolytes that are in the circuit.

Another working way to find a malfunction, when inspecting printed circuit boards, you need to gently tap the board with a screwdriver or another insulated object and listen to the speaker connected at the output or observe the output signal on the oscilloscope, if there is a bad contact somewhere, it will be indicated by noise during tapping or crackling in dynamics. But after these steps, you need to check the present AC and DC voltages with a multimeter at the terminals of transistors and microcircuits. After a faulty element is found, the most important moment comes here - to determine why this component could fail and already know the possible reasons for the future. A more detailed description will be in the next article.