Modern music center - repair by own hands

Modern music center - repair by own hands

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Music is one of the person's favorite entertainments. She accompanies him everywhere on the road, at work, studying and, of course, at home. Good music, of course, is great, but do not forget that for enjoying your favorite songs you need a quality sound. In order to achieve it was invented such an electrical device as a music center. For a long time, its electronic filling has been adjusted and improved, and everything in order to expand its functionality, in particular, to improve the sound. To date, music centers are structurally complex devices that consist of advanced electronics and modern mechanical elements. It is worth noting that the process of their modernization and repair with their own hands is still in full swing, and this despite the extensive and diverse selection of products.

Content

  • 1Modern equipment
    • 1.1Device (package)
      • 1.1.1Cassette deck
      • 1.1.2Optical disc player
      • 1.1.3Radio Tuner
      • 1.1.4Equalizer:
      • 1.1.5Built-in hard disk
      • 1.1.6Speakers
  • 2Electronic components of musical centers
    • 2.1Electronic decoder
    • 2.2Sound Processor
    • 2.3The LF (low frequency) and HF (high frequency)
  • 3The main types of malfunctions and repair options yourself
    • 3.1Does not turn on
      • 3.1.1Video: possible consequences from mounting an improperly selected fuse
    • 3.2Do not read discs, slow reading
      • 3.2.1Video: laser head cleaning
    • 3.3Do not adjust the sound with the button, periodically independently adjusts the volume
      • 3.3.1Video: cleaning the swath encoder
    • 3.4Problems with sound reproduction and amplification (diagnostic technique)
      • 3.4.1Checking the speakers (speakers)
      • 3.4.2Checking the integrity of the connection between the output connector and the copper contact tracks
      • 3.4.3Video: disassembly of the music center
      • 3.4.4Checking the output gain path
    • 3.5Harsh and distorted sound from all sources
      • 3.5.1Replacement of the UHCH chip, for example, STK 403-070
    • 3.6From the speaker can hear noise and crackling or it does not work at all
      • 3.6.1Video: rewind voice coil speaker
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Modern equipment

Musical equipment of this type is a universal device of electroacoustic type intended for reproduction and recording of audio files. It supports a wide range of audio formats that are aimed at working with various kinds of audio media.

Device (package)

Modern music centers are complex electrical devices, consisting of many complex electrical nodes and mechanical components.

Cassette deck

Represent the site for the installation of film cassettes. This component is considered obsolete, however, in certain models it can still be found. When buying a music center, you should see whether the selected model is equipped with a pair of decks. If not, it's better not to buy it, because if necessary, you can not re-record music or listen to one tape while rewinding another.

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By the mechanism of control decks are of two types: mechanical - open by pressing a button - and touch (open with the help of an easy touch).

Optical disc player

The optical disc player is an integral part of any modern device.

Appearance of the optical disc player

The main component of the optical disc player is an optical drive. In general, the optical drives included in the package of modern centers are of the universal type, which is capable of supporting a wide range of various popular media formats.

Optical drive

It should be noted that simple centers are equipped with an optical drive capable of reproducing only one disc. In more complex MCs, the drive is supplemented by a changer - a device designed to simultaneously accommodate multiple disks (usually three to seven) and consecutively play them.

Speaking of optical disc players, it's worth mentioning the ways in which you can load disks into an optical drive.

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The audio equipment market has a large number of music centers, which can be divided into devices with front and vertical loading.

  • Front loading of disks is carried out by inserting the disk in the vertical plane under the front panel. And for the rotation of the disk in the device can be observed.
  • Vertical loading is based on the direct installation of the disk on the optical drive spindle, located at the top of the center (under the cover). Before loading the disc, open the lid or move the protective curtain.

In addition to the methods described above, there are various loading mechanisms:

  • Tray is the most common type of disk loading. Before playing, the optical disc is placed on the drawer, which moves it into the interior of the optical drive.
  • The slot is a special hole on the music center in which the disc is mounted. After installation, we slightly push it and further processing will be done by the loader itself.

The following types of loading mechanisms are used in devices that are equipped with the ability to work with several disks at once. Such mechanisms include:

  • Carousel - a volumetric tray, a sliding type designed to install a group of disks, and these discs can be moved. After the disks are installed one can choose one of them and it will be moved by the mechanism to the optical drive for playback.
  • The store is a special cassette for storing disks. Before playing audio files in it, you must install the selected discs in a sequential order.

Radio Tuner

A radio tuner is an electronic device designed to receive signals that come from radio stations.

The display of the digital radio tuner MC from the manufacturer LG

Modern music centers can be equipped with both digital and analog radio tuners. All of them fulfill the same task: they provide high-quality reception of radio programs in different bands sound frequencies (FM, AM, MW and LW), however, digital type tuners have a number of analogues advantages. Among which:

  • Making better signal reception.
  • More accurate frequency adjustment, which makes it easier to detect the required radio station, using manual mode.
  • Commit user settings.
  • Ability to save settings for more than ten radio stations.
  • Stereo sound playback at FM and AM frequencies.
  • Service support, Radio Data System (RDS) providing listeners with the ability to receive messages that are broadcast by most FM stations (in parallel with the main signal).

Equalizer:

Equalizer (EQ) is a device that is used for special processing of an audio signal in a selected frequency range. It is an element that is part of almost all modern MCs, however, their device and characteristics are very different (depending on the model chosen).

Built-in hard disk

Hard disk of the music center

A device for storing audio files intended for playback and recording them directly. The capacity of hard drives depends on the manufacturer and usually ranges from 80 to 250 GB.

Speakers

Represent a device that serves to output audio information (music playback). Depending on the configuration of the center there may be a different number of columns. According to the number of speakers and their design features, the musical centers are built on the basis of three acoustic systems:

Microsystem:

The simplest models of musical centers are built on the basis of a stereopair (two columns containing one speaker each). In this case, the audio signal is divided into two parts, which are transmitted along one of the channels (broadband speaker) to the left or right.

Mini and microsystems:

They are used in more complex music centers, where more than 2 speakers are used in each speaker. In this case, the spectrum of sound frequencies is subdivided into several narrow frequency bands (subbands). Each of these bands has its own characteristics and therefore the dynamics that make up the columns have their own individual design, which is characteristic for a particular band. The difference in design causes an improvement in the reproduced sound.

Dignity - high sound quality and its purity.

The disadvantage is the complexity of manufacturing (due to the fact that it is necessary to create an individual design of each speaker).

A separate and most interesting kind of acoustic systems is a two-way.

This type of system is used in music centers using speakers that are equipped with two speakers with fundamentally different designs. In this case, the frequency band is divided into two broad bands. Typically, in systems of this kind are used: a speaker, a combined type that reproduces both low and medium frequencies, and high-frequency.

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The number of frequency bands and channels can be found in the technical description of the MC, the selected model.

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Electronic components of musical centers

In addition to the various types of acoustic systems discussed above, the following electronic components and modules are used to generate a sound signal and improve its properties.

Electronic decoder

Used to convert information that is recorded to digital tracks of a disc into a multi-channel sound signal. In the event that the music center has the latest models of decoders, it is possible to increase the format of the audio system and improve the quality of its sound.

Electronic decoder board from the manufacturer DOLBY

Sound Processor

Digital Sound Processor (Digital Sound Processor) performs complex processing of the audio signal.

Microcircuits of the sound processor

With the help of the processor, sound processing is performed, which is based on the required frequency, the number of bands, as well as the sound atmosphere of the room used as the installation site audio systems.

Earlier the sound processor was an element that was mounted only in expensive models of music centers, but now it is used practically in any centers.

The LF (low frequency) and HF (high frequency)

Realizes the possibility of rough adjustment of the audio signal through amplification / attenuation, which is performed by an adjustable high and low frequency filter.

During operation of the music centers, various malfunctions may occur, for example, electronic components and modules may fail or mechanical parts may be damaged. We will consider them below.

The main types of malfunctions and repair options yourself

The most common problems that users of music centers complain about are:

"Does not read discs"

Does not turn on

One possible cause of the malfunction may be damage or burning of a fuse located in the input circuit of the power supply.

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To perform the diagnostics, perform the following steps:

  1. Open the back cover of the music center.
  2. Disconnect all connectors from the power supply.
  3. Unscrew all the screws that fix the board, and take out the power supply.
  4. We perform a visual inspection of the board.
  5. If there are traces of burning or an unpleasant smell in the input circuit of the power supply unit (near the fuse), then replace it.
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Remember that to replace the element you need to choose a fuse of the same value (you can see it in the device diagram or on the element itself), as well as the damaged one! Otherwise, a number of unpleasant moments are possible, for example, a microchip of the right or left channel can burn.

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If after the replacement of the fuse everything is OK and nothing happened with the microcircuits, just in case, we will check them for this:

  1. Take a tester or a multimeter (we shorten both probes to check operability).
  2. Connect the power supply board to the mains (for 3 seconds) and turn it off.
  3. We transfer the measuring device to the "Voltage measurement" mode.
  4. According to the scheme of the device or the description of the microcircuit - TDA -7265 - (you can find it on the Internet) we study the legs.
  5. To the input of the chip we bring the red probe ("+"), and to the output black () ie check the passage of voltage.
  6. If this parameter is below the minimum, then we make the replacement of the chip.

The TDA-7265 also needs to be replaced if it has been burnt as a result of soldering a new fuse (see p. video possible after installation of an improperly selected fuse).

Video: possible consequences from mounting an improperly selected fuse

And also often there are problems with the amplification and quality of sound reproduction. These faults can be divided into the following:

  • There is no sound in all modes of operation (tuner, cassette deck, CD / MP 3 player, external signal).
  • Humming, poor sound reproduction from any source.
  • There is no sound in one of the speakers.
  • From time to time, the sound disappears and again manifests itself.

Do not read discs, slow reading

Such malfunctions in most cases arise due to the fact that over time, during use, the laser head becomes dirty and old. They (pollution and aging), in turn, contribute to reducing the transparency of the plastic lens. In the aggregate or one by one, these phenomena can manifest themselves in different ways, for example, after installing the disc in the music center player starts scanning media information tracks and tries to read the data, but some time later the reading stops or But the device considered the information and started playback, however, in the process there are noises accompanied by frequent malfunctions during playback music.

In order to diagnose these faults, we check the operability of the laser itself and the degree of transparency of the lens for this:

  1. Remove the body of the music center (necessary in order to observe the laser head).
    One of the possible options for the design of a laser head
  2. We open and after a few seconds, close the carriage of the player.
    The carriage in the musical
  3. We wait until the carriage returns to its original position and provokes rotation of the rotor of the motor of the optical drive.
    The optical drive motor in the music center
  4. Let's see that the lens moves in the direction "from the top down" and "from the bottom up" respectively (due to the electromagnet) along the axis of the laser head.

One of the easiest ways to eliminate malfunctions and incorrect playback of CDs is to clean the laser head, which consists of two stages:

At the first stage, we clean the lens. To do this, perform the following steps:

  1. Take a soft damp cloth.
  2. We wipe the surface of the lens (this action is performed with the utmost care).

At the second stage we proceed to clear the prism (we perform only if cleaning the lens did not lead to a positive result). For this:

  1. We take out the laser head from the device.
  2. Remove the plastic cap that covers the lens and electromagnet, which are mounted on the metal plate.
  3. We unscrew all the screws fixing the plate on the base.
  4. Raise the plate and see a small hole.
  5. We take a match and wrap it with a thin layer of cotton wool.
  6. We dip a match with cotton wool in a jar with alcohol.
  7. We wipe the surface of the prism.
  8. In the reverse order we collect the head and install it in the center.

Video: laser head cleaning

Do not adjust the sound with the button, periodically independently adjusts the volume

These faults mainly arise in the music centers, which are built on a digital control system (microprocessor). The thing is that instead of the usual variable resistor used to control the volume level, these devices use the encoder (encoder) - a special sensor.

The encoder is located under the body with the inscription "VOLUME"

Rotation of the shaft encoder causes the corresponding contacts to close. The processor, in turn, monitors the direction of rotation of the "regulator" and, based on the information received, produces a gain change in the path. Accordingly, if the contacts are oxidized or contaminated during operation, there will be intermittent malfunctions and there will be a violation of the normal sound adjustment.

This fault does not require complicated diagnostics, since it can be visually performed so we will immediately proceed to troubleshooting. In order to clean the contacts of the encoder we perform the following:

  1. We disassemble the musical center.
  2. On the front side, the dismantled apparatus we see a large printed circuit board.
  3. We disconnect from it all trains and unscrew the screws.
  4. We remove the board and find the valcoder.
    Valcoder
  5. We turn it over and evaporate the regulator.

We disassemble the encoder:

  1. We razginaem metal frame.
    Valcoder in disassembled form
  2. We take alcohol and wash the inner contact tracks.
  3. We clean the tracks from the oxide using an eraser.
  4. Wipe again with alcohol and lubricate the track with grease (you need a small amount).

After that:

  1. We collect the valcoder.
  2. Solder to the board.
  3. The board is screwed to the device.
  4. We connect loops and check the work.

Video: cleaning the swath encoder

Problems with sound reproduction and amplification (diagnostic technique)

Among specialists and novice radio amateurs, there has long been a definite method for diagnosing music centers in which problems with amplification and sound quality appear. It is quite simple so anyone can apply it. At its first stage, you need to check whether the speakers (speakers) are working and evaluate the sound quality.

Checking the speakers (speakers)

Checking the speakers is done in any case (with a hoarse sound, its absence and so on) as it will help to narrow down the range of troubleshooting and more or less accurately determine their source.

  1. We take obviously serviceable columns (you can take it from any other device) with an impedance of about 4-8 Ohm.
    Remote music speakers
  2. We connect the column to the music center.
    The connecting cords are connected to the left (L) and right (R) channel connectors
  3. Turn it on and listen to the center.

After performing these actions, there are probably two options:

  • The fault has disappeared, indicating that the speakers are damaged (faulty) and you will need to carry out repairs.
  • The fault has remained, then the machine itself should be repaired, and not the remote elements (columns).

Checking the integrity of the connection between the output connector and the copper contact tracks

At the second stage of the diagnostics, the integrity of the connection of the output connector and the contact copper tracks on the control board of the device should be checked. (only if the speakers are working), because it also affects the sound quality and can: cause a rattling or contribute to a sudden loss / appearance of sound.

In order to evaluate the quality of soldering, we perform the following actions:

  1. We'll analyze the music center.
  2. We examine the contact connections, the soldering of the output connector to which the speakers are connected.
    Output connector (two red terminals near the housing part)

Video: disassembly of the music center

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I would like to note that contact damage or poor-quality soldering is usually found immediately, as these things are clearly visible.

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In order to prevent, as well as to avoid possible degradation of soldering - small gaps between the contact of the connector and the edges of the groove boards - that are formed in the apparatus after a long operation due to overheating or high mechanical stress. It should be carried out the soldering of the contacts of the connector.

Checking the output gain path

In this case, the problems can be related to the incorrect operation of two microchips: an amplifier designed to amplify the power of the audio frequency (UHMZ), a processor, and a signal switch.

To perform diagnostics and to accurately identify the faulty chip, perform the following steps:

  1. Turn the device on.
  2. We select one of the operating modes (tuner - receiver cassette deck, CD / MP 3-player or external source, connected via AUX IN).
  3. We estimate the quality of the signal and the presence / absence of malfunction (excessive bass, sound loss of one of the channels, etc.).
  4. We check the remaining modes of operation.

In the event that the manifestation of a malfunction occurs when each of the modes is turned on, it is most likely that the cause of the problem lies in the UHFS chip. However, the cause of the malfunction may be in the malfunction of another unit of the device, for example, in the incorrect operation of the chip of the sound processor responsible for switching signals.

Such a situation can lead to confusion and serve the fact that we will look for a fault in the wrong node. In order for this to happen, we will conduct additional diagnostics:

  1. We take household headphones (you can and from the phone).
  2. We connect them to the Phone connector.
  3. Reduce the volume of the center, if it is set to a large value.
  4. Alternately listen to music in each mode of operation.
  5. We carry out the audit of the path to UMZCH by ear.

After completing these simple steps, it is possible to significantly narrow the troubleshooting area, since if the headphones reproduce a quality and "Even" sound, this indicates the correct operation of all nodes of the sound path: the sound processor, the signal switch, preamplifiers. Accordingly, a fault is associated with the part of the electronic circuit that provides the amplification of the signal power.

In the event that after the steps described above, the malfunction remains, then it means that the UHMZ chip is faulty or it works incorrectly (from two channels, the sound is played only in one channel or the sound passes through both channels, but in one of them with distortion). Accordingly, this chip (can be of different series, for example, TDA 8588J. 4 or STK 403-070) is subject to replacement with a new one.

Harsh and distorted sound from all sources

We perform the apparatus check according to the procedure described above and determine the malfunction. In the event that, according to the results of the diagnosis, the UMPF works incorrectly, it should be disposed of and replaced with a new one.

Replacement of the UHCH chip, for example, STK 403-070

Before proceeding with the dismantling of the chip, we will do the following:

  1. Mark (mark) all loops and connectors that connect the various units of the device. To ensure that after repair do not get confused when assembling.
  2. We disconnect all marked loops and connectors, as well as fasteners (screws).
  3. We pull out the amplifier board and put it on the desktop.
  4. We examine the board and find the necessary microcircuit.
    STK403-070
  5. We turn the board over and see the soldered contacts of the chip.
  6. Take the flux and spread the contacts of the chip.
  7. We turn on the soldering station and switch it to the hot air supply mode. Next, heat.
  8. We take the heated soldering iron and evenly pass through the soldering points of the contacts.
  9. After you see the process of melting the solder, with a free hand, carefully take out the microcircuit.

After the chip is soldered, do the following:

  1. We clean the pad from the solder remaining after the chips are squeezed, for this you can use a copper braid.
  2. We take a new microcircuit.
  3. Paste the contacts down to their original location.
  4. We spread the flux, take the solder, transfer the soldering station to the "Soldering iron" mode.
  5. Solder the chip.
  6. We conduct testing after repair (we connect all loops and turn on in all modes of operation).

From the speaker can hear noise and crackling or it does not work at all

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These faults can be caused by a break in the coil winding or by touching the coil winding of the magnet system of the speakers. However, before dismantling the speakers, you should check the operation of the speakers of the music center by connecting other speakers (as described in the procedure and perform other steps).

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Please note that this repair is very complicated and time consuming. It should not be performed without the proper experience and skills, as well as the availability of tools for work!

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If during the inspection of the defect path (problems with the microcircuits) it was not revealed, and the faults disappeared, then it is necessary to repair the speakers. For this:

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  1. Gently remove the speaker from the speaker housing.
    Woofer
  2. We take it out and put it on the table.
  3. We check the speaker for "rustling" (we press with equal force the points located on opposite sides with respect to the center of the diffuser).
  4. We listen attentively and determine whether there is rustling or not.
  5. If it is, we can also check the working speaker in a similar way.
  6. If there are no extraneous noise in it, the cause of the malfunction lies in the fact that the coil winding touches the magnetic system (as shown in the video below). To correct this defect, you can rewind the coil.

Before you start rewinding the coil, you need to disassemble the speaker. For this:

  1. We take a screwdriver with a flat slot (end).
    Flat blade screwdriver
  2. We support the rubber suspension of the diffuser under the speaker and unfasten it.
  3. We mark the suspension and the body (on one side) of the dynamics in order to make it easier to assemble after repair.
  4. We turn the speaker and evaporate the conductive wires of the coil.
  5. With the same screwdriver, gently weave the centering washer and unfasten it.
  6. We take out the diffuser.

The process of disassembling the speaker is over and now you can start rewinding the coil.

  1. We inspect the coil (it can be painted with black paint).
  2. For the convenience of rewinding, insert a large capacitor into the coil, preferably on the diameter of the sleeve (if the capacitance is less then wrap it with molar tape until the diameters match).
  3. We take small table clamps and fix the diffuser behind the condenser.
  4. We are looking for the end of the winding wire and snacking it.
  5. Slightly unscrew and we mark the side in which the wire is coming from the output.
  6. We unwind the coil. You can not count the number of turns.
  7. For the second wire, we also make a note of the winding direction (from the output).
  8. We take the coils with a copper wire (the diameter of the cross-section can be, mm).
  9. We select the wire (visually compare the diameters of the wire taken from the coil and the selected one).
  10. If, the cross-section of the selected wire is greater, then more wires are reeled accordingly.
  11. We take the brush and lightly clean the surface of the sleeve (the coil base) from the paint.
  12. We clean out the conclusions and tin them.
  13. We clean, tin and solder the wire to the bottom of the coil.
  14. We take glue and slightly lubricate the surface of the sleeve.
  15. Slowly and with a little stretch reel it on the reel. We look, that the winding was accurate and even.
  16. We put an additional layer of glue and let it dry (to avoid the failure of turns).
  17. Similar actions are performed with the second wire.
  18. Again, apply glue to the spool and spread it evenly.
  19. Again we clean the wire and solder it to the terminal.

Video: rewind voice coil speaker

Before assembling the speaker, we check to see if the coil is touching the magnetic system. For this:

  1. We insert the diffuser with the rewound coil into the case.
  2. We perform a test for "rustling".
  3. If there is no rustling, then lubricate the coil leads with glue and dry it.
  4. Then measure the resistance of the rewound coil with a tester (multimeter).

We build the speakers:

  1. Blow the dust from the speaker housing.
  2. We apply glue for centering washer and diffuser suspension.
  3. Install the diffuser by label.
  4. Solder the conductive wires and test the speaker.
  5. Carefully take hold of the centering washer and smoothly move it along with the diffuser, thereby achieving a purity of sound (ideally without minor distortions that may be present).
  6. After finding the desired position of the diffuser, we apply an additional thin layer of glue under the centering washer.
  7. Leave for a day to dry.
  8. Secondarily check the work.
  9. We apply glue to the surface of the column and glue the speaker.
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Remember that the work at all stages of eliminating these two faults must be done very carefully. Especially assembling a speaker with a rewound coil, otherwise with inaccurate assembly noise may remain, but the sound quality will nevertheless become higher.

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In the current market of audio equipment, all kinds of music centers are sold. Each of them has its own characteristics, which are determined by the applied components and modules used in the development and creation of the device. Some modern centers have a built-in Wi-Fi module, which allows you to go online and download music. In addition, most MCs can be re-equipped and supplemented with speakers, external acoustic systems, amplifiers, desktop EQs and other devices in one way or another associated with sound.

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