If you make an amplifier for a subwoofer with your own hands, you can select and control the sound parameters in accordance with your own preferences. When assembled correctly, it will work reliably and efficiently.
Purpose
A car amplifier is designed to increase the sound power of the audio system in the car, as well as the normal functioning of the subwoofer. This device will be useful if the standard speakers do not produce loud enough sound.
Often car radios do not have a special amplifier designed to work with a subwoofer. If you connect a subwoofer directly, the audio quality will leave much to be desired.
Main characteristics
The sound volume directly depends on the output power of the device. The higher this indicator, the louder and undistorted sound the speakers can reproduce.
The output power for a subwoofer should be greater than that for full-range speakers. Another important characteristic is the output impedance. The smaller it is, the higher the output power and current consumption of the device.
How to do it yourself
You can make a sound amplifier in a car yourself using ready-made kits. This will simplify testing and adjustment, and reduce the likelihood of errors that could lead to incorrect operation. Another advantage is that no radio engineering skills are required.
The kit for self-assembly of an amplifier consists of blocks of a limiter, preamplifier, power amplifier, crossover, stabilizer and control device. Another option is to assemble the device from discrete parts according to the diagram.
Frame
It must provide adequate cooling to amplifier components that may become hot during operation. To do this, slots or holes should be provided, which should be located as close as possible to the output chip. To improve the cooling of the powerful amplifier, a 12 V fan is installed. It will provide additional protection against overheating.
The housing can be made of plywood or metal, such as sheet aluminum or tin. In this case, it is necessary to ensure the isolation of the components and the device board. To improve shielding, you can connect the negative pole of the board to the case. It needs to provide seats for terminals that are attached to the reverse side. To avoid mistakes when connecting, explanatory notes should be placed on the housing.
Speaker amplifier
First, it is recommended to make a power filter with a fuse. Its rating is at least 20 A. The filter itself includes a choke, which can be taken from a faulty radio, and capacitors. They are combined into a battery to improve operating efficiency.
The filter capacity must be at least 6000 µF. The larger it is, the better the amplifier will perform at high volume. To automatically turn on the device, a mechanical or electronic control relay must be installed. The winding is connected to ground and the blue and white stripe wire of the radio. The contacts are connected to the positive wire gap in front of the filter capacitor.
If you are assembling a car sound amplifier with your own hands from a ready-made kit, then you should connect the blocks in accordance with the instructions. The amplifier and preamp are connected to each other using the included cables. A power stabilizer or voltage converter is connected to these blocks if more than 14 V is needed for normal operation of the microcircuit.
After this, the assembled structure is installed in the housing and secured with the elements included in the kit.
If the amplifier is assembled on a board from separate parts, then you will need to solder them to the required points. When connecting this device directly to the speaker outputs of the radio, it is necessary to provide an adjustable divider. It is not required if the connection is to a low level line output. Wire resistors necessary for protection and matching are included in the speaker terminal gap. Their resistance is 1-2 ohms.
Subwoofer amplifier
It is distinguished by the greater power required to drive the subwoofer, as well as the presence of a low-pass filter. The amplifier chip is installed on a heat sink with a larger area for more efficient cooling.
The sound power of the subwoofer can be increased by connecting it using a bridge circuit. If you need an amplifier in your car for both speakers and a subwoofer, then each channel has its own unit. The entire structure fits into 1 housing.
How to install and connect
Before installation, you should carefully check the build quality and compliance with the diagram in a garage or home. If the amplifier was assembled from discrete parts, then check the cleanliness of the printed circuit board and the absence of solder drops between the terminals of the components. The device should then be powered from a 12V car battery or screwdriver through a 5A fuse. This is necessary to reduce the risk of fire in the event of critical installation errors.
If, after connecting the power, there is a clicking sound in the speakers and subwoofer, followed by a slight noise or hum, and the fuse has not blown, then the amplifier is assembled correctly. If you touch the audio input with a screwdriver, an AC hum will be heard. If a fuse blows, loud clicks are heard, or sparks jump between the power wires and the battery terminals, then there is a short circuit in 1 or more parts.
If there is no sound, clicks or background in the speakers, then a break is suspected.
The next step is to check with the radio. It is connected to the audio input of the amplifier, and power is supplied from the same battery by branching wires. First, you should only apply power to the radio, set the volume to the lowest level to avoid overload, and then turn on the amplifier. The sound must be high quality and undistorted. Otherwise, you need to check the installation for errors.
The speakers and subwoofer are connected to the output terminals of the device, power and sound from the radio are connected to the input terminals. Do-it-yourself installation of the amplifier in the car is carried out after a complete check. The device is placed where proper access and cooling are provided.
Before I start my article, I want to say that if you have strong nerves, a lot of free time, certain skills in electronics, like to listen to very loud music in the car, powerful bass and are willing to spend a lot of money on such a project, then this article is just for you !
The idea of creating a high-power amplifier has been around for a long time, but due to lack of time and finances, the project was postponed. And then summer... vacation... It was decided to turn the idea into reality and exactly 3 months were spent for this, since there were big problems with the parts, but despite this, the amplification complex was successfully assembled and tested.
To begin with, I would like to clarify the meaning of the expression “enhancing complex”. The fact is that it was decided to assemble a high-quality amplifier that could power the entire car audio system. The entire power part (power amplifiers) had to be combined “under one roof”, the result was 5 separate amplifiers with a total power of 680 watts, do not confuse with Chinese watts, there is a pure 680 watts of rated power, the maximum power of the system reaches 750 watts.
The requirements for the complex were as follows.
1) High sound quality
2) High output power
3) Relatively simple design
4) Low costs compared to the prices of factory systems of this kind
5) Ability to power 10 -12 speakers + subwoofer
To implement this idea, 5 separate power amplifiers were used, including a high-quality Lanzar amplifier to power the subwoofer channel.
Below are the parameters and series of microcircuits that were used in this amplifier.
TDA 7384 - 4x40W (2 pieces, total power of microcircuits 320 watts or 8 channels, 40 watts per channel)
TDA 2005 - 1x20W (2x10W) (2 pieces, total power 40 watts or 2 channels 20 watts each)
The above microcircuits are designed to power front speakers. This solution is the most economical; to create an amplifier of this kind, you can find out about the monetary costs at the end of the article.
The most difficult part in any amplifier of this kind is the voltage converter, it is designed to power the subwoofer amplifier, perhaps we’ll start with it.
Voltage transformer
It took me exactly two weeks to create.
The voltage converter pulse generator (from now on PN) is built on a traditional TL494 microcircuit. This is a high-precision push-pull PWM controller, a domestic analogue of 1114EU3/4.
The microcircuit does not contain an additional output amplifier. The additional stage is built on low-power transistors, the signal from them is fed to the gates of the field switches.
The circuit is known as a push-pull or push-pull converter. The circuit is not new, but I had to change some of the circuit values to suit my needs. On each shoulder there are two powerful field workers of the IRF3205 series. Through heat-conducting gaskets they are mounted on heat sinks that were removed from computer power supplies
In the rectifier part, KD213A diodes are used, they are just for such purposes, since they can operate at frequencies of 70-100 kHz, and the maximum current reaches 10 amperes; in this circuit, the diodes do not need additional heat sinks, I did not notice any overheating.
I used 2 relays for power supply, 20 amperes each, but it is advisable to install a relay for 50-60 amperes, since the converter draws a considerable current. The remote control system (REM) is implemented in the PN, i.e. No powerful switches are needed to turn on the subwoofer. By applying plus to the remote control, the relays are instantly activated and power is supplied to the converter.
I especially struggled with winding the transformer, since the transformer was of my own design. Unfortunately, I could not find ferrite rings, so I had to go for an alternative solution.
We got several computer power supplies for free, and large transformers were soldered out of them.
The ferrite halves are tightly glued to each other, so they need to be heated with a lighter for 30 seconds, then carefully removed from the frame. As a result, the standard windings were unwound from the transformers, and the terminals were cleaned.
At the end the frames are attached to each other. The result is one elongated frame onto which we can freely wind the windings we need
Through experiments, the required number of turns in the primary winding was found. As a result, the primary winding contains 10 turns (2x5vit) with a tap from the middle.
Winding was done immediately with 5 strands of 0.8 mm wire. First, 5 turns are wound along the entire length of the frame, then we insulate the winding and wind another 5 turns on top identical to the first. We wind the windings IN THE SAME DIRECTION, for example clockwise.
After winding the wires, we twist them into a pigtail, not forgetting to remove the varnish in advance, then we tin them and cover them with a layer of tin.
Now you need to phase the windings. In fact, there is nothing difficult here, you just need to find the “beginning” and “end” of the windings and connect, for example, the beginning of the first winding with the end of the second or the beginning of the second with the end of the first, the connection point is a tap to which the plus from the general power supply is supplied ( see diagram).
After phasing the windings, we wind a test secondary winding; it is needed so that if the phasing is incorrect, we do not wind the entire secondary winding. The test winding can contain any number of turns, for example 3 turns with 0.8 mm wire, then we assemble the transformer by inserting the core halves.
When turning on the circuit, the transformer should not emit a “buzz”; the transistors should not overheat if the converter is idle. We connect a 12-volt incandescent lamp of a couple of watts to the secondary winding, which should light up with almost full heat, while the transistors should be cold and only after a few minutes of operation you can feel a slight heat release. If everything is normal, then remove the test winding and wind in its place a normal one, which is wound according to the same principle as the primary.
This time the winding is wound with two strands of 0.8-1mm wire and contains 30 turns (2x15 volts). Two identical windings are wound, each with 15 turns and stretched along the length of the entire frame. After winding the first half, we insulate the winding and wind the second one on top. The windings are phased according to the same principle as the primary.
After winding the secondary winding, the wires at the ends are twisted and tinned. At the final stage, the core halves are strengthened. The transformer is ready!
IMPORTANT! In converters of this kind (push-pull) there should be no gap between the halves of the core! Even the slightest gap of a fraction of a millimeter will lead to a sharp increase in the quiescent current and overheating of the field-effect transistors! It was because of my clumsiness that I burned several field-effect transistors. Make sure that the ferrite halves are pressed against each other as tightly as possible. Such a transformer is capable of providing the required voltage and current to power the subwoofer amplifier.
We solder the transformer onto the board and begin winding the chokes.
Throttle
The circuit uses 3 chokes. They are designed to filter out RF noise and interference that can form on the power lines. The main choke is used on the positive power line of the converter. It is wound with 4 strands of 0.8 mm wire. The ring used those in computer power supplies. The number of throttle turns is 13.
The remaining two chokes are located after the diode rectifier in the PN, they are also wound on rings from computer power supplies and contain 8 turns of 3 cores of 0.8 mm wire.
To be honest, I didn’t expect that such a high-quality voltage supply would be obtained, the quiescent current of the circuit does not exceed 200 mA, this is normal for such a monster, the output voltage is +/-63 volts, the slope is insignificant, only half a volt. The maximum power of the converter would allow powering two of these amplifier, but here it works with a large margin.
Amplifiers based on TDA2005, for low-power heads
Assembling this block took only 2 hours. During this time, two identical power amplifiers were assembled. The amplifiers were chosen as the cheapest option for low-power speakers; they can be used to power speakers located on the front panel of the car. Each microcircuit develops 20-24 watts of power and has very good sound quality.
Each microcircuit is connected via a bridge circuit; with a stereo connection, one microcircuit is capable of delivering up to 12 watts into a 4 ohm load
The microcircuits are installed on the heat sink through an insulating gasket. The volume is adjusted in advance using a regulator. At first, another board was planned, amplifiers were assembled from this one, then a general board was invented, which was entered into the project archive.
TDA 7384 for front speakers
For more powerful speakers, TDA 7384 quadraphonic microcircuits are used. Each microcircuit is capable of delivering up to 40 watts of power per channel into a 4 Ohm load. The result is 8 channels of 40 watts, sounds very good.
Such microcircuits are used in car radios; if you are too lazy to buy them, you can get them from non-working radios.
Microcircuits have different filters independent of each other; if you use a common filter, then noise and excitation are possible.
Both amplifiers start working when +12 volts are supplied from the battery to the REM pin. The amplifiers were assembled on one board, but later the blocks had to be rearranged, so each amplifier was implemented on a separate board.
Subwoofer amplifier
The famous Lanzar circuit, full description, assembly, circuit and configuration are described here, so there is no need to talk about this amplifier. The amplifier is completely assembled using transistors, has very good sound quality and increased output power. I made some changes in the diagram and below is the diagram I used to assemble it, the original diagram in the same forum thread.
Since I could not find some of the circuit ratings, I had to make some changes, in particular the emitter resistors were replaced with 0.39 Ohm 5 watts. The BD139 transistor was replaced with a domestic analog KT815G, in addition, the low-power transistors of the differential stages and pre-output stages of the circuit were replaced.
Electrolytic capacitors can be removed at the input if the input is replaced with 2.2 µF or more.
It is advisable to do the first start-up of the amplifier with one pair of output transistors with the input shorted to ground, so that in case of breakdowns the transistors of the final stage do not burn out; they are the most expensive thing in this amplifier.
Pay special attention to the installation of the circuit, monitor the pinouts of the transistors and the correct connection of the zener diodes, the latter, if connected incorrectly, work like a diode. I installed a regular quiescent current regulator, I do not advise anyone to repeat my mistake, it is better to install a multi-turn one, it can be used to accurately adjust the quiescent current of the circuit, also convenient for setup.
The output stage of the amplifier operates in AB mode, this is essentially a fully symmetrical circuit, the level of nonlinear distortion is reduced to a minimum. Due to its high performance, this amplifier belongs to the Hi-Fi category; getting 300 watts from this amplifier is not a problem. It is also possible to connect a 2 Ohm load at the output, i.e. you can power as many as two subwoofer heads by connecting them in parallel. In this case, you cannot raise the amplifier voltage above 45-50 volts.
You can increase the power of the amplifier by adding one or two more pairs of output transistors, but do not forget about increasing the power supply, since the output power of the amplifier directly depends on the power supply.
AC protection
Despite the fact that the power amplifier is quite reliable, sometimes problems can occur. The output stage is the most vulnerable part of any amplifier; due to the failure of the output transistors, a constant voltage is formed at the output. The constant disables the expensive dynamic head. Any amplifier of this kind has protection that will protect the speakers from constant voltage.
When the amplifier is turned on, the relay closes, including the head; with a constant voltage at the output of the PA, the relay opens, maintaining the head
The protection has a relatively simple circuit, contains 3 active components (transistors), a 10-20 ampere relay, and the rest is little things. When the PA is turned on, the relay closes with a slight delay. Power for protection is supplied from one arm of the converter, through a limiting resistor of 1 kiloohm, select a resistor with a power of 1-2 watts.
Low-power transistors can be replaced with any others whose parameters are similar to those used. The relay is connected to the collector of a more powerful transistor, therefore, the final transistor needs a more powerful one. From the domestic interior, you can use transistors KT 815.817 or more powerful - KT805.819. I noticed heat generation on this transistor, so I mounted it on a small heat sink. Protection and output signal indicator are mounted on one board.
Stabilization block
Bipolar voltage stabilizer provides the necessary voltage to power the filter unit and audio signal indicator. Zener diodes stabilize voltage up to 15 volts.
This unit is assembled on a separate board; it is advisable to use zener diodes with a power of 0.5 watts
Audio level indicator
I won’t go too deep into the operation of the circuit, since the circuit of such an indicator is described in one of my
The indicator uses LM324 microcircuits. It is advisable to use an operational amplifier for these purposes, since the microcircuits cost only $0.7 (each). The indicator uses 8 LEDs; you can install any LEDs that are at hand. The indicator operates in the "column" mode. The indicator is powered by a voltage converter, then the voltage is stabilized to the desired value and supplied to the level indicator. The indicator is connected to the output of the power amplifier, using a trimmer we adjust the indicator to the desired level of LED response.
Adder and low-pass filter block
The adder is designed to sum the signal of both channels, since we have only one subwoofer. After this, the signal is filtered, frequencies lower than 16Hz and higher than 300Hz are cut off. The regulation filter cuts off the signal from 35Hz - 150Hz.
Assembly
After a thorough check of all blocks, you can begin installation.
Unfortunately, I couldn’t find a case from a DVD player or anything else convenient. I attached indicator LEDs to the front panel, where the display used to be located. All boards are attached to the bottom of the amplifier through insulating washers, which in turn were removed from domestic equipment
All microcircuits and transistors are screwed to the heat sinks through insulating gaskets. It is advisable to use thermal paste; unfortunately, we do not sell it, but even without it everything is not so bad.
The input connectors of the amplifiers were soldered out of the DVD, and a connector from the car radio was used as output terminals.
My design uses only one cooler, it is designed to cool the heat sinks of the PN and TDA7384 power switches; the subwoofer amplifier does not need forced cooling, since for it I selected a huge heat sink that practically does not heat up.
The power wires of each amplifier are connected to common power terminals. REM control allows you to turn off any of the amplifiers (for example, a pair of TDA 2005) at the right time. Each amplifier is powered through relays, which are activated when positive is applied to the REM pin.
Each of the amplifiers has a separate remote control system, which is located on the contact platform on the side of the housing.
Subwoofer box
A couple of months after the start of assembly, I managed to buy a SONY XPLOD XS-GTX120L subwoofer head, the head parameters are below.
Rated power - 300 W
Peak power - 1000 W
Frequency range 30 - 1000 Hz
Sensitivity - 86 dB
Output impedance - 4 Ohm
Frequency range - 30 - 1000 Hz
Diffuser material – polypropylene
Since stores only sold laminated chipboards, and we don’t have MDF at all, we had to choose from what was available. Fortunately, we were lucky with the material. Chipboard from USSR times was perfectly preserved in the attic, thickness 22 mm.
The diameter of the FI port is 14 cm, the length of the pipe is 7 cm.
A hole with a diameter of 28 cm was cut for the head. After making all the parts of the box, it was time to assemble it. It is convenient to start assembly by joining the bottom and front of the box. First, holes for the screws were made with a drill (with a small diameter drill), and only then the screws were screwed on. Before this, the fastening points were covered with PVA glue.
There is no need to spare glue, so as not to complain about whistling later. I got a pretty good box, I worked as neatly as possible. Finally, the seams were coated with silicone on the inside of the box (silicone has an unpleasant odor, so this work should be done in a garage or outdoors). After assembling the box, I couldn’t resist, put the head where it was supposed to be and turned it on
I cannot convey this in words or even in a video, because it needs to be felt, not heard. You can feel the full volume of the box, the scope of the head, the power and quality of Lanzar, and all this is embodied in the pressure on your chest.... It’s impossible to describe in words and only then you begin to understand that everything around you is collapsing and falling apart, the glass is moving on the table by itself, the glass is starting to "swell" from pressure. In a word, everything in the house was under a “dose” of vibration.
We sold special glue for carpet, but a can of aerosol costs $25, so we had to use PVA glue. To begin with, I sanded the box; this process took me 4 hours. Apply PVA glue to the already cut carpet. After this, the box needs to be “rolled” over a pre-cut carpet. We wrapped the box, now in order for the glue to dry properly, we hammer small nails along the edges, then after drying they can be removed or left.
Then we cut out the holes for the head and the bass reflex. The head is attached to the box with ten self-tapping screws, this ensures tight contact, no additional gaskets are needed.
This alternative solution is again caused by a shortage of factory connectors.
It turned out well. A separate hole was cut for it.
On the inside, after sealing the wire, the connector hole was sealed with silicone sealant to avoid whistles and unwanted noise.
Total construction costs
Voltage transformer:
BC557 3pcs - $2.5
TL494 1pc - 1$
IRF3205 4pcs - 10$
Diodes KD213A 4pcs - $4
Polar capacitors - $10
Resistors - $2
Chokes and transformers - from old PC power supplies
Relay - from voltage stabilizer
Lanzar amplifier:
Transistors
2SA1943 2pcs - 6$
2SC5200 2pcs - 6$
2SB649 2pcs - 2$
2SD669 2pcs - 2$
2N5401 2pcs - 1$
2N5551 2pcs - 1$
Resistors 5 watt - 4 pcs - $3
Other resistors - $4
Non-polar capacitors - $3
Polar capacitors - $5
Zener diodes - 2 pcs - 1$
Other amplifiers:
TDA7388 2pcs - 15$
TDA2005 2pcs - $2.5
Resistors - $2
Non-polar capacitors - $4
Non-polar capacitors - $6
Filter block:
TL072 1pc -1$
TL084 1pc - 1$
Non-polar capacitors - $3
Resistors - $2
Regulators 3pcs - 4$
Indicator block:
LM324 2pcs - 2$
LEDs and everything else - $2
Stabilizer block:
Transistors 2$
Zener diodes 13 volt 6pcs - $1.5
Stabilizers 7815 2 pcs - $1.5
Zener diodes 7915 1 piece - $0.7
The rest is $2
AC protection:
Transistors - $2
Relay - for free
everything else is 1$
Fortunately, plugs, sockets and connectors were in stock
Subwoofer Box:
Self-tapping screws 50 pcs - $0.5
Sealant 2 bottles - $2
Chipboard - for free
PVA glue - for free
Head - $65
Carpet - $15
Results
That's all. I'm pleased with the results, very pleased! It is not possible to buy such an amplifier; amplifiers of similar power cost from $400! Although Chinese manufacturers offer it for significantly little money, quality and reliability.... In general, the amplifier turned out to be a thrice-bang success! Everything works great, all you have to do is buy a car and enjoy your hand-made amplifier, while the amplifier will work at home for now, from a powerful 12-volt power supply.
Here I will share my modest experience in the field of car amplifier repair. I hope the information will be useful to novice radio mechanics in their difficult task of restoring audio equipment, as well as to car enthusiasts who are familiar with electronics and want to repair their amplifier themselves.
To begin with, I would like to talk about how to turn on a car amplifier without a car radio and at home. Read more about this. This will be needed when repairing a car amplifier.
If you don’t have a powerful enough power supply at hand, then any one with a voltage of 12V and a current of 1 - 3 amperes will do. But here it is worth understanding that we only need it to turn on and set up the amplifier. We will not operate it at full power, so the current consumption will be minimal.
I also strongly recommend reading or taking note of the material on the design of a car amplifier converter. This information is very important.
Well, now, examples of repairs from real practice. They mainly concern one of the main blocks of any car amplifier - a voltage converter, or in other words, an inverter.
Repair of car amplifiers CALCELL.
1. Malfunction: the car amplifier goes into protection. The red PRT (Protect) LED lights up on the front panel. After a couple of turns on, the amplifier stopped showing signs of life altogether - the PRT LED stopped lighting.
The cause of the malfunction turned out to be the 2N4403 transistor in the circuit of the TL494CN chip (converter). One of his crossings was breached. In addition, a 10Ω (Ohm) resistor burned out. In the photo R7 is him. While the resistor “endured”, the amplifier turned on, but went into protection. When it burned out, the amplifier stopped turning on altogether.
Pinout of bipolar P-N-P transistor 2N4403.
Why did the amplifier go into protection? The fact is that this transistor is part of the on/off circuit. Due to the breakdown of the P-N junction of the transistor, the amplifier did not turn on and went into protection.
There was no suitable replacement for the 2N4403 PNP transistor at hand. Therefore, a risky attempt was made to take the same transistor from the preliminary stage of one of the amplifier channels. Luckily they were there. Yes, just think, I decided, well, I’ll take the transistor out of there, solder it in place of the faulty one, and check the amplifier. Oh yes, I did just that. But after a few seconds after turning it on, I smelled a burning smell. It turned out that due to the absence of one small transistor, the powerful complementary transistors of the UMZCH output stage began to get terribly warm. Fortunately, the transistors survived. Therefore, I do not advise you to “cunning” like that.
Replacing the transistor was complicated by the fact that it was stained with some kind of rubber glue that glued the barrels of electrolytes to the board.
2. The CALCELL POP 80.4 amplifier does not turn on. Safety fuses blow.
The device arrived “dead”, apparently after an incorrect connection. After a quick inspection of the parts without soldering, it was discovered that the 11V zener diode in the “piping” of the TL494CN PWM controller chip was broken. A breakdown of the TL494CN microcircuit itself was also discovered. When measuring the resistance between pin 12 (+ power, Vcc) and 7 (- nutrition, GND) the multimeter showed “0”. Apparently the amplifier supply voltage was greatly overestimated.
After replacing the TL494CN chip and the zener diode at 11V, an attempt was made to turn on the amplifier. But, after turning it on, the red PRT LED lit up for a few seconds (as it should be), and then complete silence... . The power supply from which the amplifier was powered went into protection due to overcurrent.
It turned out that one of the two groups of MOSFET transistors on the converter board was getting very hot. Transistors of the other group are cold. After checking 3 STP75NF75 transistors that were heating up, it turned out that they were broken (Source - Drain). The 2N4403 transistor, which is a buffer for this converter arm, was also broken. You can familiarize yourself with the diagram of a typical car amplifier converter (inverter) in more detail.
After replacing the 2N4403 buffer transistor and three STP75NF75 MOSFETs (labeled as P75NF75), the auto amplifier began to work properly.
3. Amplifier CALCELL POP 80.4. When the amplifier is turned on, the red LED lights up "PROTECT" and after a few seconds it goes out. The amplifier does not turn on - there is no indication.
This happens when the converter goes into protection due to high current consumption or a short circuit in the load. The load in this case is all four amplifiers, a filter block and preamplifiers.
The most likely reason for the protection to trip is the failure of the output transistors. The CALCELL POP 80.4 amplifier uses powerful bipolar transistors as output transistors. You can evaluate their serviceability using this method, and it is not at all necessary to unsolder the transistors. As a rule, a breakdown of a transistor junction is easily determined; the multimeter begins to beep unpleasantly with a buzzer - a signal that there is zero resistance between the terminals of the transistor.
It is worth considering that with such a quick test, parts associated with the transistor being tested (low-power transistors, etc.) can affect the readings. Therefore, if in doubt, unsolder and check the transistor separately. It is not uncommon that it is the elements associated with our transistor that are broken, and not the transistor itself. Some amplifiers, for example, such as the SUPRA SBD-A4240, use MOSFETs as output transistors. MOSFET transistors can be checked with a universal tester, since a conventional multimeter is not always suitable for such purposes.
Let's return to our amplifier. For greater clarity, I will refer to the circuit diagram of this amplifier - CALCELL POP 80.4 auto amplifier circuit. When checking the output transistors of one of them, the Base-Collector (B-C) transition “ringed” as if it had been broken. In the diagram it is designated as Q312 ( 2SA1694). To check the performance of the amplifier, I removed the faulty transistor and its complementary pair - transistor 2SC4467 (Q311). I turned on the amplifier, but it went into defense again. This means there is something burnt somewhere. In addition, the low-power transistors Q309 got very hot ( MPSA06) and Q310 ( MPSA56). The check showed that transistor Q309 (MPSA06) had both junctions broken.
Since there was no complementary pair 2SC4467/2SA1694 on sale, I decided to replace it with more powerful analogues - a pair 2SA1943/2SC5200 manufactured by TOSHIBA. Like this. They feel heavy to the touch and inspire confidence.
After installing the new 2SA1943/2SC5200 transistors, it turned out that they were too large and because of this the board did not fit into the case.
I had to bite out a small part of the printed circuit board so that they would fit into the case and fit tightly to the surface.
After replacement, the amplifier began to work properly.
During the electrical run, I noticed that even without a load, the low-power transistors in the preamplifiers heat up quite noticeably. When playing music with a lot of bass, the heating increases. The amplifier drove two subwoofers (one per bridge).
Perhaps long-term operation at maximum power led to overheating and failure of the low-power transistor MPSA06 (Q309), and this in turn to a breakdown of the B-K junction of the powerful transistor 2SA1694 (Q312) in the output stage of the amplifier.
4. Non-standard case. A CALCELL amplifier that had just been purchased in a store was brought in for repair. According to the owner, after connecting the power, smoke came out of the amplifier's ventilation holes.
After opening and inspecting the printed circuit board, it turned out that there were traces of solder paste and solder balls on the terminals of one of the MOSFET transistors of the converter. Here is a photo.
Apparently, current flowed through the remaining solder paste when turned on. Because of this, the rosin in the paste heated up and began to evaporate in the form of a white haze. After this, the amplifier did not turn on due to a solder bridge formed when the solder paste melted. It's no secret that cheap electronics made in China do not pass pre-sale testing. Hence these "blunders".
Repair of Lanzar VIBE 221 car amplifier.
Diagnosis: car amplifier does not turn on. No LED indication. Judging by the appearance of the printed circuit board, they tried to repair the amplifier, and even the key MOSFET transistors in one of the converter arms were replaced. Instead of the native IRFZ44N, STP55N06 were installed. But the amplifier died for a long time. Also in the gate circuit of the MOS transistors there were “burnt” but serviceable 100 Ohm resistors. When checking the 2SA1023 buffer transistors, which “drive” the IRFZ44N mosfets, it turned out that they were working.
After replacing the TL494CN PHI controller chip, the amplifier started working. Just in case, 2SA1023 buffer transistors and 1N4148 diodes in the base-emitter circuit of these transistors were replaced.
Mystery car amplifier repair.
Problem: The amplifier turns on, but there is no sound. Car amplifier Mystery 1.300 a typical representative of the so-called monoblocks. That is, it is a monophonic amplifier. The sound power declared by the manufacturer is 300W. Such amplifiers are usually used to drive a powerful low-frequency speaker, that is, a subwoofer or subwoofer.
After opening and inspecting the printed circuit board, it turned out that several transistors (2SB1367 and 2SD2058) were poorly soldered, there was solder degradation and excessive heating of the solder points. The transistors appear to be part of the 15V stabilizers in the secondary power circuits. These stabilizers are used to power operational amplifiers and amplifier filters. This node can be called differently preamplifier. It is to this that we connect the very “tulips” through which the sound signal from the car radio is sent. Naturally, if there is no power to the preamplifier, then there will be no sound.
Why did it happen? The fact is that the transistors that overheated do not have a radiator; their housing is plastic. They rely on their own conclusions. There is no additional fastening. Due to overheating and constant shaking (it was installed in a car), the soldering was destroyed and the contact was broken. Therefore, the stabilizers stopped working. Any more and the transistors would simply fall out of the mounting holes!
After restoring the soldering of the transistors, the amplifier was fully operational, but the noticeable heating of the transistors suggested that there would be a repeat after some time.
It was decided to install heating transistors on a homemade radiator to reduce heating. Also update the pin soldering and make it more reliable. This is what came out of it.
At the same time, adjacent transistors were placed on the radiator, which heated up less - to impart rigidity to the structure. Since the transistors are in a plastic case and do not have a metal flange, I also applied thermal conductive paste KPT-19 to the place of thermal contact with the radiator.
Among other things, on the printed circuit board of the monoblock there was a clearly “swollen” electrolytic capacitor of 3300 µF* 63V in the secondary rectifier. The power supply - inverter usually contains 2 electrolytic capacitors, since food amplifier stages bipolar, around ± 28 - 37 volts. The adjacent electrolyte looked better and was not “swollen”.
It was decided, just in case, to replace the electrolyte that had swollen with a new one at 4700 µF * 63V (this was available). During an electrical run of the car amplifier, it turned out that the replaced electrolytic capacitor was slightly heating up. It turned out that it was heated by powerful resistors located nearby. For reference, the neighboring electrolyte does not have such resistors nearby. This is an obvious flaw. As you know, heating has a bad effect on electrolytic capacitors, since the electrolyte dries out faster and their capacity decreases.
Repair of car amplifier Fusion FP-804.
Malfunction: The car amplifier does not turn on. No indication. After opening it, it didn’t take long to find the cause. The converter burned out all the HFP50N06 MOSFET transistors (the original was STP50N06), as well as several 47 Ohm resistors in the gate circuit of some of these transistors. The 2SA1266 buffer transistors were also knocked out.
Instead of the burnt HFP50N06 transistors, IRFZ48N were installed, new 2SA1266 buffer transistors, burnt 47 Ohm resistors were replaced, as well as a TL494CN PHI controller chip, just in case.
The device turned on and began to work properly. But my joy was short-lived. Three days later, the owner of the amplifier called me and said that a weak monotonous whistle had appeared in the rear speakers. The whistle was only heard when the engine was running.
The first thought that came to mind was interference from the generator that gets into the audio path of the amplifier. This happens when wiring has been done hastily and the supply and signal (interblock) circuits are close together. But the electrical wiring and interconnect cables were made with high quality, which I was convinced of. A day later they brought me a “dead” Fusion FP-804 amplifier with a familiar diagnosis: it won’t turn on.
The most interesting thing was that the power indicator "Power" glowed barely noticeably. But I didn't pay attention to this. After opening it, it turned out that the same MOSFETs were knocked out again. So this amplifier ended up in my scrap pile - they gave it away for parts.
After some time, I decided to restore this amplifier, and I wanted to figure out what was the reason for the widespread burnout of rather expensive mosfets in the converter. I bought new transistors to replace the faulty ones, installed them and...
At the first launch I witnessed an enchanting show. Immediately after switching on, I heard a growing whistle - a slow start of the converter, and then I saw sparks jumping from the center of the toroidal transformer.
Here it is - a malfunction! Breakdown of windings in a transformer. If I had hesitated and not turned it off, I would have completely burned out this batch of MOSFETs.
After this, it became clear why the green LED was dimly lit "Power" with 12V power connected. The current entered the secondary circuit through a breakdown between the windings of the transformer and slightly “illuminated” the power indicator LED. This is the first time I encountered such a problem. The only way out is to rewind the toroidal transformer.
Schematic diagram of the Fusion FP-804 car amplifier (aka Blaupunkt GTA-480).
SUPRA car amplifier repair.
Car amplifier SUPRA SBD-A4240.
Malfunction: Turns on normally - " green LED". But when a signal is applied to the inputs, there is no sound in any channel. The amplifier is silent.
This malfunction is not typical. To better explain the method of troubleshooting and troubleshooting, I will refer to the circuit diagram of this amplifier. Diagram of the Supra SBD-A4240 car amplifier (opens in a new window).
Measurements of the supply voltage in the secondary circuits did not yield anything - everything is normal. After a quick check, a broken 7.5V zener diode was discovered (indicated in the diagram as ZD4).
A broken zener diode led to the shutdown of the signal circuits of all amplifiers, since it was installed in the input signal blocking circuit (Q3, Q101, Q201, Q301, Q401, ZD3, ZD4).
This circuit blocks the passage of the audio frequency signal to the inputs of the preamplifiers. The signal is “blocked” for a short time, immediately after the amplifier is turned on. This is done in order to avoid “clicking” in the speakers.
Since there was no 7.5V zener diode available, a 5.6V zener diode was installed instead of the broken one (this led to slight distortion of the signal; later a 7.5V zener diode was installed). After this, 3 channels began to work with slight distortion, and 1 channel produced strong distortion with signs of self-excitation of the amplifier. When the tweezers touched the input of the sound signal ("tulips"), a periodic "gurgling" was heard in the speaker.
Suspicion fell on the block of input filters, the one implemented on operational amplifiers - KIA4558 microcircuits (in the diagram U1-A And U2-A). Therefore, in order to determine where the fault lies, the signal circuit going from the output of the input filter block to the input of the preamplifier was broken. This is done simply - one terminal of the electrolytic capacitor is soldered off (in the diagram it is C108).
Next, use tweezers to touch the output of resistor R115 or the base output of transistor Q103. Thus, we apply a “noise signal” to the input of the preamplifier. Moreover, if the amplifier is working properly, then we will hear a characteristic hum in the speakers. But in this case, along with the hum in the speaker, I again heard a nasty “gurgling”. It became clear that the problem should be looked for in the preamplifier, and not in the input filter block.
Finding a faulty element in the preamplifier was complicated by the fact that it was made using low-power transistors (in the diagram Q102 - Q116), of which there are quite a lot. Checking these transistors without unsoldering them from the board (for breakdowns of transitions) did not give any results. Therefore, it was decided to unsolder all the preamplifier transistors and check them more carefully.
This also did not give any results, although it was possible to detect two 2N5551 transistors, which caused mistrust. I checked them with a universal tester, and every other time they were determined to be broken. I had to replace them with new ones. All other transistors turned out to be in good order, as were other elements of the circuit: diodes (D3 - D5) and capacitors. BUT! I didn't check the resistors!
During an external examination, I noticed that on the body of one of the resistors (in the diagram R124 - 47 Ohms) there was a barely noticeable burnt. When checking, it turned out that the resistor was broken.
Since resistor R124 is installed in the emitter circuit of transistor Q106 (2N5551), its break led to incorrect operation of the amplifier and that same “gurgling”. After replacing the faulty resistor, the amplifier began to work properly. The Q106 transistor was also replaced with a new one. As I already said, when checking, a pair of 2N5551 transistors came under suspicion. Perhaps one of them is transistor Q106, in the circuit of which resistor R124 burned out.
Another malfunction of the same amplifier.
A car amplifier we were already familiar with was brought in for repair. SUPRA SBD-A4240 (V1M07) with “torn out” electrolytes in the secondary circuits of the converter. To my question: “How did this happen?”, the owner replied that the amplifier was in the car that was involved in an accident. As a result, the amplifier worked properly, but there was a terrible background in the speakers - impulse noise from the converter was doing its job. New capacitors with a capacity of 2200 uF * 35V were installed in place of the original capacitors. The background is gone.
If possible, then, of course, it is better to install electrolytes with a larger capacity (2200 - 4700 μF).
There are times when finding a large-capacity electrolytic capacitor is quite difficult. No problem! You can make a composite capacitor from several, the capacity of which is small. Read about how to properly connect capacitors.
Other little things.
All active elements - transistors, both field-effect and powerful complementary pairs of transistors are installed on the radiator through an insulating mica gasket. To improve heat transfer, thermal conductive paste is used.
In some cases, it is necessary to remove the printed circuit board from the amplifier housing, which is also a radiator. Naturally, the heat-conducting paste smears, stains everything around, and dust and dirt stick to it. Therefore, you have to remove it from the radiator and transistor housings, and clean the insulating mica gaskets from it. It's not a pleasant job.
After repairs, everything needs to be restored as it was. Have thermal conductive paste on hand KPT-8 or KPT-19. It is better to apply the paste on both sides, both on the metal substrate of the transistor and on the radiator. In this case, the mica will be in the middle and covered on both sides with a layer of thermal paste. I don’t recommend applying a lot of paste; the main thing is that an even, thin layer of paste forms on the surface.
I advise you to also buy mica for the occasion. For example, I bought a mica plate measuring 10 * 5 cm and about 1 mm thick. Mica can be easily “flaked” using a sharp knife blade. Get several insulating pads made of mica. They can be used to replace broken, damaged or lost insulating gaskets. Mica can be easily cut with a knife into plates of suitable size.
Where can I get parts for repairs?
When repairing a car amplifier, parts are often required to replace faulty ones. It happens that you cannot find such ones. Where can I buy? You can buy radio components online. For example, I ordered on AliExpress. It is not always possible to find what you need in our online stores.
If you don’t want to spend money on expensive audio gadgets, you can try to assemble a car amplifier with your own hands. This operation is not at all difficult. The main thing is to approach its implementation competently.
1 Amplifiers - how not to get confused in their classes?
Many audio systems in modern vehicles are equipped with a special built-in device that allows you to achieve greater sound volume and music quality. Unfortunately, such a standard car amplifier does not always cope with its tasks. Its power is simply not enough. In such cases, you have to purchase another device that can increase the current and voltage of the sound signal to a certain level.
Nowadays it is easy to purchase almost any car amplifier that is more powerful and of higher quality. The only question is how much you plan to pay for this device, which is important for lovers of good music. Car amplifiers for reproducing high-quality sound are usually divided into different classes depending on the purity of the signal they produce and the efficiency indicator.
A minimum of distortion is ensured by a car (relatively inexpensive) class A amplifier. But its efficiency does not exceed 20%. B-class devices are more powerful. Their disadvantage is a significant distortion of the reproduced music. The golden mean in this case can be considered class A/B devices. They are characterized by average values of sound purity and useful action.
Car amplifiers of the indicated classes can have a different number of channels - from 2 to 5:
- three-channel audio devices allow you to connect two speakers to them;
- in two-channel car devices, only speakers can be connected;
- four-channel ones can operate in tri-mode (one mono and two stereo systems are connected to one output), and a subwoofer is additionally connected to five-channel ones.
There are also high-power bass amplifiers. They are called monoblocks. The cost of such devices is high. Therefore, a monoblock car amplifier is purchased quite rarely and by those car owners who are not used to saving on anything.
2
When choosing a modern car amplifier, you first need to decide on its class, and then on the number of channels. And only after that begin a substantive analysis of the technical capabilities of the audio device you are interested in. How to choose a car amplifier in practice? Pay attention to the following characteristics:
In addition, it makes sense to understand the number of car amplifier connectors. Expensive devices have a variety of linear and high-amplitude inputs. The first ones are necessary for connecting equalizers, processes and other systems to the audio system. And without the latter, you will not be able to install a radio in your car without a linear output.
3
Experts in the field of radio electronics say that transistor and microcircuit audio amplifiers cannot be compared with ULF devices in terms of the quality of the sound produced. Any pro will tell you that a tube car amplifier will delight you with excellent music without any distortion.
At the same time, you can assemble such a sound amplifier with your own hands in a couple of hours and with minimal financial costs.
Tube amplifier
A tube auto amplifier can be made using a simple single-ended circuit. It is shown below. This circuit is good in that it allows you to increase the output power due to the parallel pairwise arrangement of light bulbs working on the load.
Let's see how to assemble a simple car amplifier at home using the diagram below. You need to take the audio output and power transformers from the old TV, find (or purchase) an unused power supply and light bulbs. It is advisable to place products marked 6N2P at the entrance. And a 6P14P lamp is more suitable for the output. If you cannot find an old power supply for a homemade car amplifier, you will have to buy a new device. Choose any. The main thing is that it is designed for 50 Hertz and has windings for the specified voltages.
Focusing on the diagram, you assemble all its elements into one whole (as you yourself understand, without knowledge of the basics of radio electronics it will be difficult to do this). Then you look for a suitable housing to house a homemade car amplifier. As such, you can use an unnecessary case from the system unit. You don’t even have to remove the fan from it - it will blow on the tube amplifier. The fan should not run continuously. Therefore, be sure to make a switch for it. Place this device on the back of the system technician's case. You will turn it on only as needed.
Tube amplifier
You can make your car amplifier more elegant and practical by illuminating its bulbs with multi-colored diodes. Then, when the audio device starts, the lamps will glow, for example, green, in standby mode – blue, and so on. That's all the wisdom of self-assembling a simple amplifier for a car. Believe me, it will not differ much from an average-priced factory device, and will even surpass it in sound quality.
4
Semiconductor elements make it possible for any craftsman who has the skills to perform simple electronic work to make a small semiconductor amplifier for his car. Let's see how to build an excellent audio device using the TDA8560Q chip. Instead, you can use TDA2005, TDA1558, and any other circuit that produces the following (approximately) characteristics:
- frequency range – from 20 to 20000 Hertz;
- power (output) – 25–40 W;
- power supply (voltage) – from 6 to 18 V.
To make a car semiconductor amplifier, you need to purchase all the required elements: capacitors and resistors (0.2 μF), a transformer (power) with a current of up to 5 A, a cooling radiator, a power switch, sound balance and volume controls, diodes marked D245 ( or their analogues), capacitor (electrolytic) 25 V x 4700 µF, connectors (output and input). You assemble all these components according to the circuit on a printed circuit board, solder them, and solder a thin wire into the power traces. Then mount the manufactured structure on the cooling radiator. Your little sound amplifier is ready!
Auto amplifier on TDA chip
Now you should think about how to correctly connect a car amplifier. Everything is simple here. Assemble the power supply yourself (diagram below) and connect it to the on-board network. More on this later.
5 Connecting and setting up homemade and factory audio devices
Let's figure out how to connect a car amplifier yourself. If you have never done this kind of work, it is recommended to purchase a special set of electrical wires designed specifically for this purpose. A ready-made set will allow you to quickly connect an amplifier (made yourself or factory-made). True, the sound quality in this case may not be the best. You can achieve ideal sound by using separate stranded copper wires:
- 2x4 for subwoofer;
- 2x1.5 for tweeters;
- 2x2.5 for rear and front speakers.
Any wire can be used as power wiring. It is usually connected to the car body with a minus, and to the power output of the radio - with a plus. But car audio pros recommend connecting the amplifier a little differently - directly to the vehicle’s battery. In this case, you will have to spend money on a more expensive and thick wire KG-35 or KG-25. It must be connected to the existing terminals on the battery. The remaining wires (between the speakers and individual sides of the audio system) are also connected to terminals and special outputs.
Setting up a car amplifier yourself, as a rule, does not cause serious problems. This operation should be performed strictly according to the instructions included with the factory sound amplification device. And homemade “gadgets” are adjusted using sound balance and volume controls, which, as noted above, are mounted in semiconductor and tube amplifiers.
