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Car amplifier repair channels do not work. Car amplifier repair. Cost of repairing car power amplifiers

After all, as they say in the narrow circles of radio mechanics - “In electronics there are only two types of faults”:

1. Presence of contact where there should not be.
2. Lack of contact where it should be.

List of technical equipment required for repairs:

1. Screwdrivers of various designs, side cutters, pliers, assembly knife, tweezers, magnifying glass - that is, what is needed at a minimum for repairs.
2. The measuring device is multimeters.
3. An adjustable bipolar power supply for 16...24 or 36v, preferably with an output current limiting function.
4. And lastly, experience in electronics repair.

Determining the malfunction should begin by checking the output voltage - whether it is there or not. If it is missing, the fuse may simply have blown, there is no reliable contact at the wire terminal, etc. The moment is standard and ordinary, but it is at this stage that in 10% of cases the repair is completed.

The next steps when you start should be: - search for a circuit diagram for the amplifier; if you can’t find it, then you’ll have to rely on your experience and knowledge. We remove the cover of the device and begin a visual inspection of the printed circuit board to identify leaks or swelling of electrolytic capacitors, blackening of resistors, broken printed tracks, etc. Sometimes only such an inspection makes it possible to quickly identify a part that has failed. Then, with the amplifier turned on, you need to check all the components installed on the board with a touch of your finger. If strong heat is generated on the element, then it can be assumed that this may be the problem.

Car audio amplifier repair- this is troubleshooting not only in the sound amplification path, but also in the main unit of the amplifier - the power source. We examine the power supply and output voltage. Basically, automobile ULFs have bipolar ones from 20v and more. If we find blackened resistors or broken transistors, we replace them with serviceable ones.

The actual sequence of checking actions is as follows:

We turn on the amplifier, after applying voltage, you need to short-circuit the Remout input to the “+” power supply (or to “-” in different ways everywhere) and observe the Protect protection indicator, if the LED lights up, therefore, the amplifier has switched to protection mode. This can happen due to a malfunction of the voltage conversion module or a broken transistor junction in one of the arms. Also, the cause of the breakdown may be the lack of power on the microcircuit installed in the transistor circuit of the converter (usually TL494 or others are installed there).

In addition, the protection of a car power amplifier can also be triggered if one or several UMZCH transistors of one of the channels are knocked out. When the transistor of the output stage of the PA is knocked out, a short circuit occurs, creating a colossal load in the PN circuit. As a result, the protection is immediately activated.

Therefore, continuing car audio amplifier repair, and after turning on the power to the amplifier the fuse remains intact, then you need to check the output voltage on the converter, which should be 2 x 20v or more (bipolar). Most likely, when the protection indicator is lit, there will be no voltage in the output voltage circuit. Based on this, it is necessary to disconnect the PA from the converter. One of the most convenient options may be to unsolder the transistor leads one at a time on each channel or unplug them all. After the terminals of the MOSFET transistors are unsoldered and the amplifier turns on normally, the protection LED does not light up. Then we use the method of ringing transitions to find the broken field field and change it.

If the LED continues to light when voltage is applied, then we continue to look for a fault in the converter. First of all, we determine whether there is voltage on the PN microcircuit; transistors in the voltage supply path to the microcircuit may burn out. Pay special attention to the transformer, see if there are any singed turns of the enamel wire or a break. It would also be a good idea to sniff to see if there is a burning smell. In some models of car amplifiers, diode assemblies are installed in the converter circuit between the amplifier, which can also cause the protection to trip.

An audio amplifier is a device where the signal passes through series-connected stages. Troubleshooting is carried out using a fairly simple algorithm, so the question of how to repair an audio amplifier with your own hands is not too difficult. The only condition is the availability of measuring equipment. A conventional tester can detect some defects, and the presence of measuring equipment such as an oscilloscope and an audio frequency generator will allow you to repair the device efficiently and quickly.

How to fix an audio amplifier

Troubleshooting low frequency amplification systems must be performed in a specific sequence. This will avoid mistakes and waste of time. Repair of an audio amplifier begins with an external inspection. In this case, you can easily notice torn wires, broken conductors or mechanical damage to individual elements. Since all parts of the sound system that are exposed to too much current change, inspection will reveal defects associated with electrical damage in various circuits. On permanent resistors, the paint completely burns off, and the printed tracks on the board are often damaged. Defective electrolytic capacitors can be easily detected by swelling in the upper part of the cylindrical housing. Typically, such damage to radio components is not a cause, but a consequence of another malfunction, therefore, after eliminating visible defects, it is not recommended to turn on the device, but all cascades should be checked sequentially. The first thing you can do is ring the speaker system and check for an open circuit between the amplifier output and the speakers.

power unit

Checking the audio frequency device should start with the power supply. Most units use simple transformer power supply circuits, and only some designs use pulse voltage converters. If the defect in the audio frequency system is unknown, then before checking, the power supply should be disconnected from the main circuit. This can be done by cutting the printed tracks. Testing the power supply begins with measuring the output DC voltage. If it is very high, you need to check the regulating transistor and zener diodes.

If there is no voltage, check the diode “bridge” and the presence of alternating voltage on the secondary winding of the power transformer. The tester should check the electrolytic capacitors of the filter. A bipolar power supply is checked in a similar way, since the electrical circuits at “+” and at “-” are usually the same. If there are faulty parts, they should be replaced and the presence of DC output voltage checked.

Amplifier path

The next step is to check the output stage. A common malfunction is the breakdown of power terminal transistors. If the device fails during operation, you need to touch the housings or heatsinks of the output semiconductor devices with your finger. Strong heating of the radiator indicates that the transistor is broken. Using the tester, you can easily check the base-emitter and base-collector junctions. If there is any doubt, it is better to remove the transistors from the board. In order to properly repair an audio amplifier, one tester is not enough. To work you will need a low frequency generator and an oscilloscope.

If the power supply and output transistors are working properly, you need to look for defects in the pre-final and preliminary stages. To do this, a signal from a generator with a frequency of 800 Hz-1 kHz and an amplitude of 100 mV must be sequentially applied to the cascades of the audio frequency unit and the passage of the signal through the speaker system must be controlled. When repairing structures with high output power, you need to use an equivalent load instead of speakers, and monitor the signal with an oscilloscope.

Designs assembled on specialized integrated circuits do not have discrete elements. The board may contain power filter capacitors and input capacitance. In this case, any diagnosis does not make sense. If the supply voltage of the device is normal and there are no breaks in the input and output circuits, then the microcircuit will have to be changed. In automotive systems, defects in printed wiring are common faults. Such violations occur among Chinese manufacturers. Poor-quality soldering is damaged by shaking and vibration, and the automotive low-frequency unit fails.



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Do-it-yourself audio amplifier repair Currently, more and more users of audio equipment who have at least some skills in electronics prefer to repair their sound amplifier with their own hands

Everyone knows that modern and inexpensive audio equipment is mainly produced in China and, of course, it cannot be compared with Hi-Fi class equipment, not only in terms of the parameters declared by the manufacturer, but also in terms of build quality, operational reliability, and sound qualities. and of course the lack of technological capabilities regarding normal repairs. Therefore, most lovers of natural sound independently maintain in working order both Soviet-era equipment and used imported equipment. Especially lately, due to their cheapness, power amplifiers of imported manufacture in faulty condition are entering our markets. p>

This article will describe purely practical tips that I use during the renovation process. Therefore, if you have certain skills and desire, you can repair the sound amplifier yourself at home. Most failures of amplifiers or similar devices are indicated by the absence of an input signal, or when the mains voltage is turned on, the high-voltage fuse or fuses in the DC circuit immediately blow. In this case, the fault is most likely located in the output stage of a device assembled with transistors or a hybrid circuit using integrated circuits. If the mains fuse blows when turned on, there is a high probability that the power supply is faulty or there is a short circuit in the high-voltage circuit; there may simply be a simple short circuit in the mains plug or wire. Nevertheless, start doing audio amplifier repair should be in this order: before proceeding with direct troubleshooting, you need to conduct a visual inspection of all components, 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 the containers.

After a thorough visual inspection, you can start doing it yourself DIY audio amplifier repair, having prepared in advance the necessary tools and measuring instruments. I always start troubleshooting from the final circuit of the amplifier, and only after identifying a non-working cascade should I look for the problematic part there. With the power of the device turned on and applied to the input signal circuit, without using measuring instruments for now, you need to touch the surface of the housing of powerful transistors or microcircuits installed on the cooling radiators with a dry finger, thereby determining the approximate temperature of the element. If no heat is felt at the output switches, this means there is no current in the circuit, which actually should have heated the transistors or the microcircuit. And if, on the contrary, it is impossible to hold your 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 the capacitors, they must be replaced; this is true for all electrolytes that are present in the circuit.

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

A low frequency amplifier (LFA) is a device whose purpose every music lover knows. This component of the audio system allows you to improve the sound quality of the acoustics as a whole. But like any other electronic devices, the AC can fail. Learn more about how to repair car audio system amplifiers yourself in this article.

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Typical faults

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 so many of them. The main task of repairing a sound amplification device is to restore a broken component, the failure of which led to the inoperability of the entire board.

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

  • contact is present where it should not be;
  • There is no contact in the place where there should be contact.

Functionality check

Repair of car amplifiers first begins with ULF diagnostics:

  1. First you need to open the case and carefully inspect the circuit, use a magnifying glass if necessary. During diagnostics, you may notice damaged components of the circuit: resistors, capacitors, broken conductors or burnt out board tracks. But if you find a burnt-out component, you need to take into account that its failure may be a consequence of the burnout of another element, which in appearance may seem intact.
  2. Next, diagnose the power supply, in particular, check the output voltage. If burnt out resistors are identified, these elements will need to be replaced.
  3. Apply power to the ULF and the Remout output, then you need to short-circuit the system to positive and look at the PROTECTION diode indicator. If the light comes on, this indicates that the device has been protected. The reason may be poor power or its absence on the board, a broken transistor, or problems with the operation of the voltage converter. In some cases, the reason lies in the breakdown of the transistor power amplifier for one of several channels.
  4. If, after power has been applied, the fuse element does 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 broken circuits. Smell this element, it may smell burnt. In some ULF models, a diode assembly is installed between the PN output and the amplifier - if it fails, the assembly can also include protection.

Troubleshooting

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

  1. If a transistor in a car amplifier breaks down, then before directly replacing it, it is recommended to diagnose the power supply safety element. 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 need to be changed.
  2. For more specialized repairs, you will need an oscilloscope. By installing the device probes on pins 9 and 10 of the generator board, you need to make sure that there are signals. If there are no signals, then the driver is changed; if there are signals, then the field-effect transistor elements are replaced.
  3. Capacitors are changed much less frequently during the repair process - as practice shows, this happens infrequently (the author of the video is the HamRadio Tag channel).

Basic Amplifier Settings

Now let's move on to the question - how to set up a car amplifier? There are several configuration options - for use with or 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 this, adjusting the audio system settings with an equalizer, the system is configured to suit your preferences. The volume must be set to maximum and turn on some track. How to set it up for use with a subwoofer - the procedure is also not particularly complicated.

For proper 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;
  • As for the rear crossover, it is set to the LP position, and the Low control must be set in the range from 60 to 100 Hertz.

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

If you don’t understand anything about this, it’s better not to go there, because repairs will cost more after you burn or break.

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