DIY car radio repair

Aradio is a very common electronic device. With rare exceptions, this undoubtedly useful device is not present in the car. The evolution of car radios is the video recorder and the car CD / MP3 player. But despite changing the recording medium in a car player, these devices are still referred to by the familiar word. car radio... It has been well established since the massive use of car cassette players.

Danny section of the site is devoted to the issues of repairing car radios with your own hands. It's no secret that car players of various modifications and manufacturers break down.

Non the pages This section will not be a simple listing of specific malfunctions of certain car radio models, but methods of repair and restoration of these devices will be revealed. The presentation will be conducted without interrupting practice, with examples of repairing specific models of car turntables.

Introduction article. It describes the necessary devices that will be required in the process of repairing car radios.

How to connect a car radio or car CD / MP3 receiver to a computer power supply (PSU)? Anyone who wants to "power" a car radio from a 220V network faces this question. This makes sense if you plan to repair the car radio or upgrade it to a stationary music center.

Here you will learn about typical car player malfunctions and their causes.

What is a complex malfunction and how can error codes help in car radio repair? A real example of troubleshooting a complex malfunction of the Pioneer DEH-P3500MP car CD receiver.

When repairing disc car radios, it is often necessary to disassemble the CD mechanism. Shown in detail is the method of disassembling the CD mechanism, which is widespread among modern car CD / MP3 players.

CD drives for car receivers of different brands differ in their design. This means that you need to be able to disassemble CD mechanisms of different types. Here you will learn how to disassemble the CD drive of the Kenwood car radio without errors.

An article that tells about one of the typical malfunctions of car CD / MP3-receivers - there is no display backlight. How to fix this breakdown will be discussed.

Here we talk about an atypical breakdown of the Mystery MCD-778MP car CD / MP3 receiver. A real example of repair using an oscilloscope.

The volume control of the car radio does not work? The knob may be the cause of the problem. The rotary encoder is very often used in digital equipment to adjust various functions and control the device. Is it really necessary to replace the rotary encoder if it does not work correctly? How to restore the correct operation of the knob and avoid replacing it is described in this article.

In the practice of repairing car players and CD-receivers, there are cases when a schematic diagram, information on the pinout of the connector or a table for decoding error codes is needed. This information is contained in the service manual for a specific car radio model. You can download the service manual for some models of popular car radios by clicking on the link above.

Which brand of car radio should you choose? Read this article and this question will disappear forever.

Find out about the device of SD / MP3 car receivers. Among all kinds of modifications of car radios, so-called flash car radios have found their place under the sun. This article examines the device and the elemental composition of car SD / MP3-receivers without a disk using the example of the Velas V-201U model.

The car radio, like any other device or mechanism in the car, can fail. As practice shows, the repair of car radios is usually carried out in the event of improper operation of the device or in the event of malfunctions not related to use. In this article, we suggest that you familiarize yourself with the main causes and methods of eliminating audio system breakdowns.

It's no secret that over time, the mechanical elements of a multimedia system tend to wear out. So, if the system does not turn on or off, it is necessary to either repair or replace it.

But first, let's figure out the main reasons why the radio tape recorder does not work:

1. Dirty device. If the radio tape recorder stops working, this may be due to contamination of the mechanisms - dirt or dust can accumulate between them, especially if the system is used in harsh conditions. As a rule, optical or mechanical components break in this case. One of the signs of contamination is a disc that is stuck and cannot play properly.
2. Also, mechanical failures can be the reason. This type of failure is usually associated with the power circuit. If the connection of the head unit was made incorrectly initially, or the electrical circuit is characterized by sharp drops, then there is nothing to be surprised at. The first symptom of problems with the power circuit is the lack of screen backlighting or the inability to start the radio.

Car audio system board

Before removing the radio from the car and starting to repair it, read the list of faults specific to audio systems. Getting and repairing the car radio from the car is not such a problem, but before you pull it out, you need to know exactly what to repair.

1. Perhaps the problem is the lack of power at +5. If you decide to get the device and repair it yourself, first of all you need to pay attention to diagnostics of the second contact of the CN701 connector. It should have a voltage in positive territory of 14 volts, this voltage should be transmitted to the collectors of the transistors. If there is no voltage, repairing car radios consists in replacing transistors or a zener diode.
2. There is no power activation signal. Before repairing car radios, you need to check the voltage of + 4.8 volts at the fortieth contact of the IZ901 controller. You should also check for a pulse on the third contact of the controller.

Dialing a multimedia system with a multimeter

Repair of car radios on your own or by a specialist is required if there is no sound volume or when the volume is increased and the tracks are played, the sound fills.

There may be several options:

Why does the radio tape recorder not read a USB flash drive or disc after starting the engine? The disk is stuck, stutters, the system does not see the USB flash drive?

The reasons may be as follows:

1. The radio tape recorder does not read the USB flash drive, does not see the disc, or the disc stutters or is stuck after starting the engine. Perhaps the device simply does not understand the recording format. Repair of radio tape recorders in this case is not required, you just need to burn the disc in a different format.
2. If the system does not see the disc when starting the engine, the disc is stuck, stutters or heats up, this may be due to contamination of the optical lens. As mentioned above, problems in the operation of buttons and the device as a whole after starting the engine can be associated with dirt. In this case, the problem is solved by using a special cleaning disc. The operation of such a disk is carried out in accordance with the requirements specified in the instructions. You can self-clean the system by blowing the elements or cleaning with a cotton swab.
3. Another reason may be the lack of laser current; you can get rid of such a malfunction by adjusting it.
4. Inoperability of loops and wires. Perhaps, during the operation of the car, the screws inside the structure simply loosened, or it could be a leakage of resistors.

Buttons do not work - there are several reasons. First, it may be mechanical damage to the buttons. To restore the functionality of the buttons, you need to disassemble the front panel and check the condition of the contacts. Perhaps the contacts from the buttons simply leave and they need to be re-soldered. If the button is inoperative, then it will have to be changed.

Secondly, the problem with the buttons may be due to a software malfunction. The malfunction is solved by rebooting the audio system and returning its functionality to the factory configuration. All settings will be erased from memory. After returning to factory settings, the device must be turned off for a few minutes.

If the radio tape recorder heats up and turns off arbitrarily, there may be several reasons:

1. The system heats up and shuts down as a result of poor power supply. Lack of power will cause the radio to turn off arbitrarily, or this is due to power failures. When the radio tape recorder heats up and turns off, you need to check the power cable - it may just come off or break, then it will have to be changed.
2. The device heats up due to poor ventilation and turns off when overheated. If the system heats up, this indicates insufficient ventilation. Such a malfunction is relevant for Pioneer radio tape recorders and, as car owners of such systems assure, there is nothing to worry about. But if the system heats up constantly and turns off at the same time, you need to think about additional ventilation.
3. Sometimes the device turns off due to software glitch. You can try to solve such a malfunction by resetting the radio to factory settings.

Hello everyone. Guys, if your mafon is broken, you don't need to take it in for repair. You can fix it yourself.

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The radio does not turn on. I disassemble and see if there is any external damage. A solder burst on the power connector.

No electronic device, including a car radio, can last forever. No matter how high-quality the audio system is, it can fail, and there can be many reasons for this. In what cases the car radios are repaired, and what malfunctions are typical for head units - we will talk about this below.

For what reasons, the radio tape recorder in the car does not work and turns off when the engine is started, why does the device not turn on, does not see or read a USB flash drive, fonit and stutters, warms up?

First, we suggest that you familiarize yourself with the main causes of malfunctions:

1. The system stopped working due to contamination of the internal mechanisms. If the radio is used in harsh conditions, dust and dirt can accumulate inside, and this, in turn, can cause damage to both optical and mechanical components of the device. If a disc is stuck in the device, then this is most likely due to pollution.
2. Mechanical malfunctions can also be the cause of inoperability, as practice shows, in this case, malfunctions are usually associated with the power circuit. Such problems can be caused by incorrect connection of the system. The system may not have enough power, causing it to turn off when the volume is turned up.
3. Fuse blown. As you know, fuses and relays are responsible for the operation of all electrical appliances in a car. It is possible that the fuse installed on the car radio itself is out of order.
4. Failure of the device itself.

So, how to get the head unit and repair the radio with your own hands, we suggest learning about the main problems in the operation of the systems, as well as options for their elimination. Where to get your car radio repaired? In any specialized service center, but now we propose to find out how to repair such a system at home.

What reasons can lead to such a malfunction:

1. In most cases, the reason lies in the fact that +5 power is not supplied to the device. In this case, after dismantling and disassembling the device, check the pin number 2 on the CN701 connector. A voltage of 14 volts should be applied to this contact, subsequently it goes to the collector elements of the transistors. In the event that there is no voltage, then most likely you will have to change the transistors or zener diode.
2. No power-on signal. In this case, the diagnostics is reduced to checking the voltage level at pin 40 of the IZ901 controller. In addition, we also recommend that you make sure that a signal is received at contact number 3 (the author of the video is Dmitry Epishev).

If the audio system is working, but there is no sound, or the sound is muted or phonet, then there can be many reasons.

They all depend on the specific situation:

Why does the head unit not play data from a memory card or disc, how to remove it if it is stuck?

Such a malfunction can occur for the following reasons:

1. Most often, such problems are associated with the fact that the audio system does not perceive the format of a music track recorded on a disc or flash drive. There is no need to repair such a radio; you need to record music in a different format.
2. Often, problems with playing tracks, as well as stuttering discs, are caused by dirty optical components, in particular, we are talking about the lens. If the system really does not function due to contamination, then this problem can be solved by installing a special cleaning disc in the drive. Read the instruction manual for the disc before use. If such cleaning does not help, then you can try to blow through the internal components of the system with a vacuum cleaner or disassemble the device and clean the optical lens with a piece of cotton wool.
3. The problem may be due to a lack of laser current. In this case, you can get rid of the malfunction by adjusting the laser beam.
4. Malfunctions in the wiring or loops. In the course of prolonged use, the screws in the structure of the device may loosen, in which case they just need to be tightened. If there is a leak in the operation of the resistor elements, then the damaged parts must be replaced.

If the buttons do not work, then first of all this may be due to their mechanical damage. In order to get rid of such a problem, you will have to disassemble the device, in particular, you will need the front panel on which these buttons are installed. After parsing, it is necessary to diagnose the state of the elements - there is a possibility that the malfunction is associated with the disconnection of the contacts. If so, then they need to be re-soldered. In the event that the button is out of order and nothing can be done, then it will need to be changed (the author of the video is the Radioblogful channel. The solder's video blog).

In addition, the inoperability of the buttons is often associated with malfunctions in the software part. With such problems, you can try to restart the device, if this does not help, then you need to return its settings to the factory settings. Naturally, this will remove all configuration from memory. If you return the device to the factory configuration, then before further use it will need to be turned off for 2-3 minutes.

What to do if the audio system is constantly warming up and turns off on its own:

1. The failure of such a plan may be due to poor nutrition. If there is no power, then the radio will not start, but if we are talking about power failures, the device will turn off for no reason. First of all, you should diagnose the supply wire - there is a possibility that it has moved away from the connector or is damaged, in the latter case, the wire must be replaced.
2. The car radio can overheat due to inadequate ventilation, and as a result of overheating, it will, of course, turn off. Judging by the reviews of our compatriots, such problems are more relevant for head devices from the Pioneer manufacturer, in which case overheating will not come in serious problems. If the device heats up very much, and also turns off arbitrarily, then you should consider additional ventilation for the system.
3. Malfunctions in the operation of the device can also be caused by malfunctions in the software part. In this case, again, you can try resetting the entire system configuration to the factory default.

The video below shows the procedure for repairing the Pioneer radio tape recorder, in which there is no sound (the author of the video is the Radioblogful channel. Video blog of the solder).

Video uploaded by Ruslan Usmanov
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Detailed description of disassembly and assembly of the car radio. Repair of the radio (does not read discs).
Service center "Rbt-Kazan" - repair of household appliances.
Tel. 8 (843) 297-99-22, 8 (843) 290-54-64
Gvardeyskaya 16a, office 9.>

Replacing the touchscreen on the MYSTERY MDD-7700DS car radio. In this video, we will change the resistive touchscreen on the car radio. I will also tell you how to check a resistive touchscreen. I will tell you about the problems that may arise during installation, as well as methods of solving them. The touchscreen took here 7 ″ 167mm * 93mm

Video instruction for connecting the Prology CAP-1.0 / 1.5 / 2.0 and CAD-1 / 1.5 condenser

Multimedia center with built-in LCD screen 177mm (7 ″), TV tuner, SD slot and Prology DVS-2145 USB interface, video overview of functionality.

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The player does not read the dvd disc. When the player does not read a dvd disc, but reads a cd disc, there are several possible reasons. The first reason is a malfunction of the spindle motor. The second reason is a malfunction of the optical converter, as well as all other elements in one way or another related to reading information from the disk. You can learn more about what to do if the player does not read a dvd disc from the course on repairing dvd players - https://my.housecope.com/wp-content/uploads/ext/439 link to the channel-

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when you take off the ponel the LED is on, whether it should be on or not

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I connect red with yellow and turn on the plus - it is silent and the panel is dark

Added by (13.07.2014, 16:18)
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Quite often, owners of car radios with a retractable display are faced with a situation when their favorite radio tape recorder stops responding to touching the touch screen, responding to pressing control buttons, and as a result, the display stops transmitting information to the user. The reasons can be of different nature. From simple contamination of the inner parts of the turntable with dust to the failure of various parts, mechanisms and microcircuits. The most common malfunction of car radios is the wear of the loop connecting the retractable display with the connector of the main board of the radio. And such advanced brands of multimedia producers as "Pioneer" or "Prology" are not insured in this situation.

Of course, there is no instruction in the documentation for replacing and repairing a loop for a radio tape recorder, because the breakdown described above requires service intervention.In addition, with frequent bending of the loop at the servo drive and display, a complete replacement of the entire loop is required, which means it will entail serious financial costs. This is one of the most common serious breakdowns of car radios with a retractable display from Prology and Pioneer.

Loops

Strange as it may seem, but this situation can happen to the owners of the player in a year, and maybe in 8-10 years. Even if you repair the loop in a service center, paying a lot of money for the service, no one will give a 100% guarantee that after some time you will not have to contact the same service center masters again with a similar malfunction.

Many people ask the question, is there a budget option for solving the task of replacing the loop? Is it possible to change the loop of the Prology or Pioneer radio tape recorder without causing damage to the family budget?

For example, to purchase a flat cable for a Prology radio tape recorder, MDD-716s / 719ts dvu-700 models, you need to spend an average of 1000 rubles for a Chinese analogue, which is not known for how long it will not fail. The same is true with Pioneer radios. The Chinese loop for the Pioneer AVH-3500dvd radio tape recorder costs about 800 rubles, and for the original one you will have to pay an average of 3500 rubles. As we can see the difference on the face and this, not counting the prices of service repairs.

Radio Pioneer AVH-3500dvd

But the solution to this issue still exists. If you wish, you can make budget repairs with minimal financial costs, but you will have to spend some time, since the work requires accuracy and skills in handling tools. But with a positive outcome, you will be able to use the car radio for several more years, and maybe decades.

For clarity, we will repair the loop of the Prology MDD-714 radio tape recorder. It should be remembered that many models of the MDD-7xx series are structurally similar to each other, which means that the instructions can be applied to any 7xx series players. For the repair, a number of accessories for the tools will be needed:

• frame with a train;
• stationery knife;
• FFC connector;
• universal loop;
• heat-resistant tape;
• soldering iron.

Disassembled radio tape recorder

Consumables are readily available from the radio electronics market and computer hardware stores.

You can figure out how to remove the radio tape recorder from the car and disassemble it yourself. On the Internet, there are many videos on solving this problem. Let's move on to the main thing.

In nature, there are two variants of a malfunction, a rupture and a break in the loop. Having retreated about a centimeter from the tail to the servo, we cut off the damaged train. We clean and tin the end of the remaining train. At this stage, we need a pre-prepared FFC connector; it needs to be soldered to the tinned end of the loop.

It is good if the number of connector positions coincides with the number of positions in the loop. If there are 3-5 more positions in the connector, then there is nothing wrong with that. We are preparing a universal train. It should be slightly longer than the original train we cut off. If the number of positions on the universal cable is more than on the display connector, then the extra ones must be cut off. You need to cut them off with a margin so that when connected to the display connector, the cable is tight enough in it. We connect.

Flat cable for top radio tape recorders

For the reliability of the fastening, we glue the connections with heat-resistant tape so that our cable is held tight and does not accidentally fall out of the connector. Putting everything together in reverse order and connecting.

Important to remember! Cut off the train in the places with the best fastening of it, in the places where it does not move. Thanks to this, the connection will be fixed and practically immobile.

The above technology of resuscitation of the "killed" plume has been used for several years and has not proven itself positively. In the same way, you can easily repair the loop for the Pioneer radio tape recorder, since the radio tape recorders are structurally quite similar. The advantage of this repair method is that if, for some reason, the loop fails again, then it can be easily replaced with a new one by removing the damaged area. In financial terms, it will not be expensive, but in time such work will take only an hour and then with small smoke breaks.

When replacing BA3917 with BA3918 in a PIONEER vehicle, conclusions 10-10, 9-11 (AM / FM).

13.) CLARION ARX-3470 Fault: The FM receiver does not automatically pick up even-numbered stations. Solution to the problem: put a 2K resistor on R824. After installing the resistor, it is necessary to discharge the capacitor for the power supply of the car radio (it is enough to short-circuit the positive and frame wires between each other). Otherwise, the receiver will tune as before until the capacitor itself is discharged.

14.) TOYOTA CROWN 93. The standard amplifier is in the trunk - 4 powerful outputs + a subwoofer. All 4 outputs suddenly failed, only gurgling sounds, the subwoofer continues to work. There is a preamplifier board in the amplifier - the painfully familiar capacitors in the red shell 100mkf10v are immediately striking - they flow godlessly! The electrolyte eats through the tracks. In Toyota radio tape recorders, 99 percent of electronics failures are associated with these capacitors - change without hesitation!

15.) CD-changer CDC-M3. German. He worked in tandem with his fellow countryman BLaupunkt Paris RM104 with a data adapter. Started to fail when reading a disc with the effect of driving over bumps, even in the garage. Cleaning the optics didn't help. After investigations, rubbing of the laser head plume on the bottom of the case was found. It can be seen that there, in their homeland, the train once freed itself from the adhesive tape fastening it, but then they forgot to return the tape back. Eh! Germans. You would have our problems, and yours for us!
The loop, of course, was restored by stripping and soldering with MGTF wire, fortunately, it does not work for bending in this place.

16.) ALPINE CDA-7873R. Does not read CD. Doesn't even try to start. Knowing the owner, he asked how it happened.
It turns out that he was driving around a hedgehog running across the road in his BMW. At a speed of more than 150 km / h. Well, in a ditch.
BMW died, but the radio and the owner remained almost intact. Only CD does not read (for some reason))). I checked the broach of the laser, bent something, adjusted it, but found nothing else. It turned out that BMW took a terrible blow mainly on the bottom. Aha! This means that the plate has crouched on the axis of the disk rotation drive. Raised to the desired height. And everything is ok. This ALPINE is tenacious.

17.) DAEWOO AKF-7331, AKF-9255XV and many other models where Asians like to place the tuner KCF-201VA, KCF-203, KCF-205. FM band does not work. Or it works only after warming up. Or just frozen (in the garage in winter), and when the car warms up, it goes down. In any case, you can try to strongly warm up the tuner case at the soldering point of the case bus on the top cover with a 40-watt soldering iron for 15 to 30 seconds. You will receive FM reception. But not for long. From 0.5 - 5 days in winter and up to a month in summer. And do not look for non-propane, although there are always enough of them there and of course they also need to be eliminated. If you calm down on this, wait for guests with a complaint after a while. The reason is in the communication coil, or rather in the ill-fated implanted capacitor in this coil. This has already been written in the secrets of repairing TVs No. 509 - in some detail.

18.) GRUNDIG SCD5290 RDS (GR0945) Processor with mask E59B. The radio tape recorder is constantly trying to start up with an illumination of the scoreboard. At the same time, there is no information on the board. Altering the EEPROM in the processor did not give any results. The defect disappeared when cooled from the chlodon cylinder of the radio board. The malfunction turned out to be in a capacity of 100.0x10 volts. It stands under the LED mechanism close to the radiator of the voltage stabilizer.

19.) In Chinese-made radio and audio players, crackling and wheezing often appear in the volume control. Replacement is hard to find. The defect can be eliminated by screwing on the rivets that connect the potentiometer leads to the carbon track.

20.) Opel SC202 I got a typical glitch: when the relay is turned on, it pops and falls off. The relay is powered by BAW70 SMD diodes. One of them is supplied with 12 volts across 10 ohms (SMD). A break in this resistor leads to such a defect - the weak link

21.) FREIBURG CR43 BP2475, CR42 BP1475 In both radios, a processor with a mask 8 925 900 474 is used. When turned on without a card, it turns on as expected with a CARD request. But if you insert a native card, it additionally displays on the FM display and freezes. It is required to change the EEPROM in the MC68HC05B6 processor.

22.) FREIBURG CR43 BP2475, CR42 BP1475 Both radios use a processor with mask 8 925 900 474.When turned on, there is only a backlight of the scoreboard. It is required to overwrite the EEPROM in the MC68HC05B6 processor.

23.) BMW REVERSE RDS (BP3836) P / N 7 643 836 341. Processor XC86515CFN 8 925 901 009 (68HC05B6). The radio turns on without asking for a code. The receiver is configurable and works without problems. We insert the cassette, the engine starts, but the head does not fit. We take out the cassette, and the engine continues to rotate until you reset the power from the radio. Reason: The processor EEPROM firmware has flown. It is required to change the processor.

24.) BLAUPUNKT SC202 (C) Made in Malaysia GM0202 7 642 852 521. Processor ZC408800CFN 8 925 900 612 mask 1C14H. Defect: the code is entered, the radio turns on, the receiver works, but the mechanic does not work! The EEPROM firmware in the processor has flown. It is required to overwrite the EEPROM of the processor.

25.) MERSEDES BENZ SPECIAL (BE 1350) Processor: SAB 80C535-N T40 / 85 (342) BIOS: NM27C512QE (250); LABEL: 1350 35/94 Memory: 85C82 I / SM smd. Some buttons do not work. Rather, only 3 and 4 work, so the native code cannot be entered. We redo the firmware and set the code for example 33333. Enter it. The radio turned on immediately without confirmation. Receiver tuning turns on and does not stop. The problem is in the oxides under the buttons themselves. With a tester at large limits, we measure the resistance on all buttons and look for a leak. In my case, the oxide is under the two buttons. Two cases in 2 months.

26.) PANASONIC CQ-DP33EU. Laser. On the UPD75112GF processor. Conversion from American mode (search step 0.2 MHz) to European. Solder the 47kOhm chip resistor in the place marked R625 (to the 16th leg of the processor). You will get a step of 0.1MHz.
For more “careful” ones, the option of a step of 0.05 MHz is offered. The same resistor, but on the adjacent pad under the nickname R626 (to the 17th leg of the processor).

27.) Reconstruction of car radios from the American standard (tuning step 0.2 MHz FM and 10 kHz AM):

Pioneer KEH-2600 (percent PD4502A) - move the R603 4.7kOhm resistor to an empty pad under R601. And if you come across a "Jap" (76 MHz - 89 MHz) - then you have a similar resistor soldered to R605 or R506, or both together. For us, only R601 is useful, delete the rest.

SONY XR-C5300R (RX, RV), XR-C5400R (RX, RV), XR-C5200R, XR-C4200R and others with percent. series MN101C09—- MN101C12—- (variants are possible, the last 3-4 characters in the number are unimportant). The 6th leg of the processor (DST SEL) is removed from the ground by desoldering the chip resistor R532 with a nominal value of 100 kOhm and suspended at +5 volts.

28.) SONY XR - C 35 0 restructuring of the grid from the American standard (tuning step 0.2 MHz FM and 10 kHz AM) Processor MPD 17708 GC - its 22nd leg (DSTSEL) at a voltage of about 2.5 V our grid, at a voltage of 3.5 in Japanese grid, at voltage 0 or 5 in American grid.

29.) Sony XR-C453 RDS The power was not connected properly. After replacing the UMZCH NA13157, the radio tape recorder started working, all the button commands from the panel were executed, but the indicator on the removable panel did not light up (the indicator backlight lamps were on) and the button backlight LEDs did not light up (the LEDs are mounted in the button body). When checking, in the socket, 2 punctured SMD zener diodes at 6.2V D903 and D905 (on the case designation 6-2) were found, they stand at the input of the connector. After replacing the zener diodes, the socket worked normally.

30.) LG TCC9310 Reverse works either in one direction or in both directions. The defect is typical for this model (4 cases). When you click on the corner of the board with the optocoupler, the triggering becomes less frequent. Cleaning the optics and gear does not help. I stuck foil from a different CVL to each gear segment. Working. Looks like the optocouplers are of poor quality. Next time I'll try to change them. If someone went the other way, write.

31.) I would like to share the secret of tuning the frequency of the receiver without loss of sensitivity. As you know, there are 2 main methods of frequency tuning. This is, with the help of a converter and switching of the broadcast grid by the processor with the tuning of the tuner. But there is also a third method, which I have tested in several car radios. As you know, the processor in car radios constantly monitors the frequency of the FM local oscillator and with the tuning voltage maintains the local oscillator frequency with great accuracy. And for this you cannot simply switch the broadcasting grid or change the local oscillator frequency in the tuner. In general, the method is this, we take a 2-band tuner from the car radio and solder it in parallel with the "native" one, except for the local oscillator output to the processor, cut off the output from the "native" one, solder it from the installed one, and you're done. It is very convenient in Japanese car radios where you cannot switch the broadcasting grid.

32.) To convert the JVC KS-RT515 car radio to the European standard, it is necessary to solder the diode, which is located closest to the processor on the board.In the figure, it is indicated as D1, if you solder D2, the radio tape recorder will operate in the range from 74 to 90 MHz, and if you solder D3, it will only scroll through odd stations.

33.) DENON DCT-A100. Laser pickup problem. The original head is successfully replaced by SANYO SF-C93AQ at the price of $ 15.

34.) PROLOGY KX-2000R Fault: the cassette does not spin, the speed of rotation of the drive is floating... Wrong value of resistor R317. Replace with 4.7 kOhm or install an additional 1.3 kOhm in parallel.

35.) PROLOGY CMD-100, CMD-120 Fault: does not read MP3 discs, does not read MP3 discs with a high bit rate (over 192). Wrong value of resistor R224 and R225. Replace resistor R224 by 150 kOhm, resistor R225 by 18 kOhm (15 kOhm) on the CD control board.

36.) PROLOGY MX-7010 Fault: the cassette does not spin, the radio wheezes. Defective transistor Q203. Replace Q203 (2SC3203).

37.) PROLOGY ZX-9050, ZX-9090 Fault: does not load discs. The presence of a disc in the radio is not detected. The discs are loading, but the disc does not spin up. Defect of one of the capacitors (C25, C26, C56) on the CD control board, the voltage at the VREF point when loading the disc is 0 Volts. Replacing C25, C26, C56 on the CD control board with new ones. Denomination - 0.1 uF.

38.) PROLOGY ZX-9050, ZX-9090 Fault: does not read MP3 discs. Crash when reading MP3 discs with heating... Defective capacitor C3 (very rarely C4) on the CD control board. Substitution C3 - 820 pF, C4 - 940 pF.

39.) PROLOGY ZX-9050, ZX-9090 Fault: does not read discs (Er2), the disc spins up with jerks, the laser lens is trying to adjust. Defective laser. RF0 level is below 0.7-0.9 replacement of the laser with a new one.

40.) PROLOGY ZX-9050, ZX-9090 Fault: sound disappears with heating when playing CDMP3 on both or one channel. Defective capacitor C15 or C14. Replacing C14 (C15) with a new one - 0.1uF.

41.) AIWA CT-FX727M, came with a malfunction - there is no sound. I checked the amplifier separately - it works fine. Adjusts the sound of the TDA7313, working over I2C with a processor. The signal came to her, but there was no way out. The replacement gave nothing. The study revealed that at pin 27, the I2C amplitude is only 0.8V. The problem was in the resistors R926 and R927 (22k ​​each), one of them was open circuit, going from + 5V to the I2C bus

42.) SDA 4331-2 is in MB COMAND 2.5 This microcircuit breaks down on the VDD2 power supply (21 legs are broken to GND).
A certain percentage of microcircuits can be “cured”. We solder the microcircuit and supply power to 21 and 24 legs (briefly 1-2 seconds), about 8-9 volts (observing the polarity) from a power source designed for a current of 2 Amperes. If the burn is successful, the above pins are called by the device as a diode.