In detail: DIY repair of radio stations from a real master for the site my.housecope.com.
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Many have Chinese radios in the kitchen, today we will tell you how to fix a very common breakdown with our own hands. This article will not open America to experienced radio amateurs, but it may well come in handy for novice Samodelkin. Today we will talk about how to fix the most common breakdown - crackling when working and adjusting the volume. It often happens that the receiver lives quietly and calmly, no one drops it, does not water it from the kettle, but it starts emitting a terrible rattle when trying to make it louder or quieter, and sometimes it is not possible to find the point at which the sound volume will be comfortable for you ...
The reason for this breakdown is that a low-quality variable resistor (in the form of a wheel) is installed in the receiver, on which the resistive layer quickly wears out and the contact no longer walks along the resistive layer, but along a rubbed groove in the glass-textolite base. Our experimental exhibit is a very common cheap Chinese radio receiver KIPO KB-308AC
So let's start repairing. We unscrew all the screws connecting the case, we see the board with the details.
Carefully unscrew the screws that secure the board to the case and very carefully lift the board. The fact is that from the reverse side to one of the components (variable capacitor) there is an indicator plastic plastic that runs along the display and shows the frequency to which the receiver is currently tuned.
Then we find our variable resistor and unscrew the wheel.
Having removed the wheel, you will see a plastic gasket, carefully pick it up and take it out.
And finally, before you is the hero of the occasion in all its glory.
The photo shows those trenches about which I spoke above, rubbed with a slider in the resistive layer.
Now, with the help of a match, we apply grease without skimping, here you cannot spoil the porridge with oil, you can fill the entire volume. Well, we collect in the reverse order.
We turn on, and….it still cracks! Turn off the receiver, turn the regulator from extreme to extreme position about 30 times and ... Voila, everything works! The volume is adjusted softly and smoothly, like on his native conveyor in the Chinese village 🙂!
I hope the article will be useful to someone, during my life I have repaired many receivers in this non-tricky way.
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This question is often asked by sloppy users of civilian technology. The problem occurs quite often and requires widespread consecration. The repair of this malfunction is quite simple and can be performed by any user familiar with the soldering iron.
Polarity reversal is one of the most common problems that beginners and even experienced users of the civilian range who decide to independently install communication equipment in a car. The problem is that, through inattention or not on a sober head, the radio station is connected to the power source in reverse polarity, not (+) to (+), and (-) to (-), but vice versa. In this case, the fuse located on the positive power cable burns out. When you try to replace it with a spare one, it also burns out. Especially gifted people replace the fuse with a bug and the fuse in the car's wiring circuit already burns out. As a rule, this already sobering up unlucky experimenters, and after that the radio is handed over for repair.
However, it should be remembered that such a malfunction is the result of a gross violation of the rules for operating the radio station and the warranty does not apply to such things! And since there is no guarantee, you can climb inside the station without any obstacles.
Let's figure out why a breakdown occurs, and why climb inside the station, if, according to the logic of things, you just need to replace the fuse?
In fact, everything is somewhat worse than it seems. For reasons of economy or out of concern for repairmen, the manufacturer puts diodes inside the station that do not fully meet the requirements of protection against polarity reversal. Further, I will give all the illustrations and photographs using the MegaJet MJ-600 radio as an example. However, a similar method of protecting the station is used in 90% of radios and, having understood the principle, you can easily fix this malfunction in other stations.
Let's take a look at the diagram. We are interested in the power supply circuits at the input of the radio station. We find the CN2 connector, and next to it the protective diode D20, marked as 1N4002.
As you can see, the diode is turned on so that during normal switching on, the cathode to (+), the anode to (-), the current does not go through it. However, if we change the polarity, a current will flow through the diode, and the current will be much higher than that for which it is designed.
Let's refer to the technical documentation for the 1N4002 diode.
As you can see, the maximum current through the diode is only 1A, and the station fuse is 8-10 watts, usually 3A. If a current more than its rating flows through the diode, then a breakdown of the semiconductor will occur and the semiconductor will become a conductor, in other words, a jumper.As a result, the current in the circuit will exceed 3A and the fuse on the cable will burn out. Naturally, replacing the fuse with a new one without repair will lead to the combustion of a new fuse.
What to do? You just need to replace the protective diode.
We open the radio station, for the MegaJet MJ-600 we will have to remove both covers and find the protective diode on the board. As a rule, it is located close to where the power wires connect to the board.
It is necessary to remove the old diode from the board and solder in its place a similar one or one calculated for a higher current, for example, 5-7A, in this case, with the next polarity reversal, the fuse will burn out before the diode and it will be possible not to climb into the station.
Another protection option is not a parallel connection of the diode, but a series one, up to the filter capacitance.
In this case, it is best to use a Schottky diode with a current of 3-5A higher than the peak consumption of the station during transmission. You can also put a regular diode, but the Schottky diode is better, since the voltage drop across it is less, which will help not to lose precious volts of the station supply voltage, and therefore the output power. If connected incorrectly, the walkie-talkie simply will not turn on. Another bonus of this inclusion is a significant reduction in the "howl" from the engine generator, if any.
In your hands, dear reader, the first book published in Russia on the repair of portable radio stations. Don't let her out of your hands.
This book provides a description of thirteen models of seven types of mass portable radio stations available in the markets of Russia and the CIS countries.
Basic and structural diagrams of radio stations, individual devices and integrated circuits as part of radio stations are presented.
Methods for regulating radio stations and individual devices are given, as well as several methods for troubleshooting, using the simplest instruments available.
The book is intended for a wide range of readers familiar with the basics of radio engineering: students of colleges, colleges and schools of the radio engineering profile, specialists professionally engaged in the repair of radio stations, and finally, users and owners of radio stations, familiar with the basics of radio engineering.
Dear wearable radio users!
Problems started with your radio station, purchased long ago or not:
¦ You hear, but no one answers your calls: it looks like the transmitter of your radio station is out of order;
¦ You hear no one and nothing: the receiver is out of order, although the transmitter may still be in working order.
You are already thinking about purchasing a new radio station, and it can cost a lot of money. Take your time, dear reader.
In this book, you will find detailed troubleshooting techniques that will help you restore your radio to work, and it will cost much less than the cost of a new radio.
Please, take into account that purchasing a new radio station does not always guarantee getting rid of any problems, because there is practically no reliable equipment, especially radio equipment.
For successful repair work and high-quality repair of your radio station, you must:
¦ clearly understand the principle of operation of your radio station according to the basic electrical diagram;
¦ study the arrangement of devices according to the wiring drawing or wiring diagram in order to be well oriented in the arrangement of functional units, devices and individual elements on the circuit board;
¦ have in stock the necessary minimum of measuring instruments and be able to use them;
¦ have, finally, certain and necessary skills for performing installation work on replacing radioelements, including large integrated circuits.
In the first chapter of the proposed book, a brief summary of the theoretical foundations of modern radio stations in general, and portable ones, is given.The composition and design of modern radio stations are presented. A brief description of the purpose and principle of operation of radio stations, receiving and transmitting devices and individual functionally complete units and blocks is given.
The next seven chapters describe the technical characteristics and design of several models of the seven types of portable (wearable) radios; the procedure for finding and eliminating possible malfunctions and methods for regulating (tuning) the receiving and transmitting devices of all models of radio stations; finally, electrical wiring drawings, schematic electrical and structural diagrams of radio stations, individual blocks, assemblies, devices and large integrated circuits are presented, and a description of their operation is given.
The first portable radio stations - of special (in certain sectors of the national economy) application - appeared on the territory of the USSR about thirty years ago.
In recent decades, radio markets. Russia and most of the CIS countries are literally flooded with a multitude of models of radio stations, produced mainly in non-CIS countries and at a number of Russian factories. ‘
At the same time, there are no enterprises for the maintenance and repair of portable radio stations even in Moscow. And users of wearable radios are essentially on their own.
Documentation (technical descriptions, diagrams, instructions) for old radio stations has been lost by many, and for new imported and new domestic ones is practically absent.
This book presents the basic electrical and structural diagrams of thirteen models of seven types of radio stations, domestic and foreign; a description of the principle of their work and methods of troubleshooting are given; methods of regulation of radio stations using available instrumentation are given.
On the diagrams given in the book, the capacitances in microfarads, resistors in ohms, and inductances in microhenries are given without letter designations.
This experience is for a beginner who has reached the moral right to be called a "teapot" from electronics. That is, someone who already knows how to turn on a soldering iron, who understands the difference between radio components, well, at least in appearance and knows that these are electronic components. At the same time, he who has an enduring desire to bring back to life one of the electronic devices gathering dust in his closet, and with the condition of mandatory success. For starters, let it be an old radio “Ocean-209”, perhaps even an old one. It is serviceable, but it is simply not possible to use it. The reason is, for example, not quite adequate sound reproduction. The first thing that needs to be learned and throughout the entire event to remember is that "in one sitting" the repair can not be overpowered, so do everything thoroughly and during the repair, do not really rely on your excellent memory, but make notes and even a photo of what you have to do in the process. He began by searching the Internet for information, and in full, about the radio receiver being restored. This is an operating manual, a diagram of the arrangement of blocks and assemblies on the chassis of a radio receiver, a schematic electrical diagram, wiring diagrams of printed circuit boards and a list of assemblies and parts used in it.
After reading the instructions and studying the circuits of the radio receiver, I unscrewed the screws and removed the back cover, side case and front panel.
I did not burden myself with super complicated tasks, but simply, as advised by most of the luminaries of electronics, I decided to check the health of electrolytic capacitors and variable resistors, to replace the unusable ones. To do this, I removed separate units of the low-frequency amplifier and power supply from the chassis. When performing this operation, it is best to cut the connecting wires in half and put on a piece of cardboard with a written serial number at each end. There will be two cardboard boxes, but the number on them is the same.As for the wires, it is still necessary to install new ones during assembly.
I started with the power supply as the most understandable unit. It is clear from the schematic diagram that its transformer is designed to work with both 220 V and 127 V mains voltages. to get rid of 🙂
Having measured the resistance of the input windings of the transformer, I revealed the average tap for 127 V, bit off the bare end, wound it up with a ring and isolated it. The presence and location of electronic components is especially clearly visible on the wiring diagram. There is only one electrolyte of interest to me. I solder it, discharge it and measure the capacity - it is not enough to the norm of 60 μF, but the ESR probe shows the minimum allowable resistance. Therefore, I decide to put it in its place and in parallel to it solder another capacitor with a capacity of 100 μF, somewhat larger than what is lacking, but for the same voltage - 25 V. ESR acceptable value. I did it, applied the mains voltage of 220 V to the power supply unit and measured the output received - everything is normal, the power supply unit is working properly.
Now the sound amplifier. Everything is more serious here.
I find seven K50-12 electrolytic capacitors on the board, which are very ancient in appearance. I move the wiring diagram closer to me and unsolder one leg from the board from each container. Naturally where possible. Where not, the capacitor is completely evaporated.
You can completely evaporate everything, there is a mounting, but it may not be there, and then it will save a lot of time and nerves.
I checked the ESR with a probe. The one in the photo (91 millivolts) corresponds, according to the conversion table for this probe, somewhere over 30 ohms. According to the tolerance table, it can be seen that a capacitance close to 50 μF x 16 V has a limit of 1.3 ohms.
The rest, except for two, have about the same. They are not suitable for further use. For two electrolytes with a permissible ESR value, the measured capacity corresponds to the ratings - you can leave it.
I installed the necessary serviceable electrolytic capacitors on the board and removed the variable resistor - the volume control, there was too much crackling in the speaker when it was rotating. I connected an ohmmeter to it and when it rotated I saw a real "leapfrog" on the display, it was in places the current-carrying path inside its case was erased. I put a serviceable identical variable resistor and assemble the amplifier board to its original position. Now check. The output is a suitable speaker, 9 V power from a laboratory PSU, and any Chinese mini receiver-scanner can be used as a sound source. The sound is clear and there is no noise when turning the knobs.
The HF-IF unit remains. He did not take it off, and there was no need. It had poorly proven electrolytic capacitors of the K50-12 brand, so the bodies of the components were simply bitten out with side cutters and their conclusions were left on the board, to which new serviceable capacitors were soldered. The power supply and sound amplifier are back in place. Once again, having checked the correctness of the soldering of the connecting wires, I connected the radio receiver to the network. Everything worked and, most importantly, it was better than it was. And may all your work end in success, Babay.
Hello everyone, today I found a Chinese FM receiver KIPO in the attic, but what's the difference what it's called - they are almost all the same in design and scheme. I appreciated the state by eye - it seemed like everything was buzzing, the mains plug was really torn off, stripped the wires and into the outlet - silence. Yeah, we disassemble, we see everything is good, and then it dawned on me that he had been buggy for a long time, the frequency was gone, the volume disappeared, I wanted to repair it, but my hands did not reach, but no one knows how he ended up in the attic, or maybe I still remember. Let's go further - appearance.
We disassemble the receiver. To begin with, let's remove the battery compartment kryshka to see if there are bolts, no - we go further and unscrew all the bolts except for the one under the antenna. It cannot be touched, it only holds a telescopic antenna. There is another hidden bolt under the handle.
So we remove the handle carefully so as not to break it, there we can see the hole on the right side, unscrew the bolt and finally remove the cover. We will unsolder all the wires, but remember where which one was.
I began to think that this was a worn out variable capacitor (with which we adjust the frequency) and, of course, a variable resistor (volume). Let's check. We solder the variable capacitor, since I found the same board from the receiver in the bins - here is the resistor and capacitor donor.
Below in the photo I have already soldered a variable capacitor, and clamped the contacts of a variable resistor with tweezers. Hurray, the receiver is alive!
Since the getinax is very fragile, especially the Chinese one, the tracks are very difficult to tolerate heating, they instantly peel off, broke a little but soldered the variable resistor, and to be sure, fixed it with hot glue, like this.
I forgot to say, the FM receiver is built on the popular SONY CX16918 microcircuit with very good parameters, in the future I will make another radio receiver with a sound signal amplifier on this microcircuit and so on - winter is still ahead.
They brought me the Alpinist 320 receiver for repair with a complaint that the receiver does not catch anything but noise. But instead of simple repairs, it was necessary to expand the range of received frequencies, up to 95-108 MHz. It was decided to use a ready-made radio set.
There were a number of problems: the supply voltage of the module is limited to 7.5V, but it is better not to risk it and power the board from 5-6V, and the power supply of the receiver is 9V, a quick and hasty decision to use a roll. The internal antenna is ferrite and not suitable for FM. I removed a telescopic antenna from another radio receiver. And I bought the missing variable resistors without any problems, while the volume control left its own, although the recommended resistance is 100K according to the scheme, but the voltage between the extreme terminals is 1.25V, and I used an 8K variable resistor without any problems.
Here is the current look of the insides of the radio
But the decision to apply the roll was hasty, we have a classic power supply on one transistor, the only thing I needed to change was a zener diode, and from 9V I got 5V, there was no such zener diode, but there were two powerful ones at 2.7V, but got 5.2 - 5.3V due to a fall
Now we just take out the old insides and instead of them we attach the board of the new receiver
We solder the power wires, adjustments. ... Please note that the maximum frequency and volume are obtained by grounding the middle terminal of the variable resistors, and not by pulling it up to the power source!
To simplify the construction, I removed all unnecessary parts of the board, leaving only the resistor mountings. The antenna was soldered to a piece of PCB, which was screwed to the old PCB mount.
That's it, the new radio is in the old building, the reception is confident and clear.
JLCPCB is the largest PCB prototype factory in China. For more than 200,000 customers worldwide, we place over 8,000 online orders for prototypes and small batches of printed circuit boards every day!
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Good afternoon. Today I want to describe the repair of a radio receiver made in China. I am wary of any Chinese electronics. Because not a single Chinese product that fell into my hands had the quality of even a small C grade.
And so, we have just recently purchased a radio. In operation was only once in nature.
The complaints are as follows:
- Very bad reception (initially)
- The tuning wheel does not spin well (it constantly sticks) - this problem arose in the middle of the day of the first and last operation.
The product did not fall or fall, did not dip into the water.
We proceed to the visual analysis.
This is how the product arrived 🙂
It is immediately clear that there was contact with the sand 🙂 We will fix this with a needle. Carefully clean each cell with a needle and push the sand out of the speaker. Or even easier. We use an old dry toothbrush and brush slowly.
Next, we proceed to disassembly.
Here is a small screw hiding.
Another bad habit of Chinese craftsmen is to collect plastic items with screws! Several disassembly or non-calculation of the force and you need to screw in a screw of a slightly larger diameter.
There is another screw under the cover holding the batteries - we also carefully unscrew it.
We open the receiver very carefully and very carefully. Chinese craftsmen are very fond of saving on everything and do not want to make detachable connections. Therefore, the wiring connecting the units of the device is thin and their length is "stretch". Therefore, in order not to cut off any wire and then not look for a long time where it fell off - do not use force!
Bad reception problem resolved. As shown in the picture above - the wire connecting the antenna and the main board is broken. To figure out where to solder it, you need to remove the main board and look at the "seal".
Gently unscrew both screws holding the PCB.
Solder the broken wire to the RC loop output. The platform is brought out to the side of the elements (indicated by 1 in the figure). The second is a capacitor that forms a circuit with a coil, which is near the site for the antenna wiring (indicated by 1).
Reception will be! Now let's deal with the frequency wheel.
The first thought that struck me was that it was time for the air condenser before it even started! :) :) :)
But no. To my amazement, it turned out to be even easier. It's just that the Chinese geniuses did not screw up the bolts located under the wheel and which hold the air condenser. Therefore, the wheel clings to the bolt head and does not spin.
We twist them to the end. We put the wheel in place.
Putting the receiver together, inserting the batteries and listening to the radio!
Thank you for your attention. I hope I helped someone.
A blog for novice radio amateurs who want to make their first radio station with their own hands, to master and understand how the receiver and transmitter work. The author introduces you to a simple radio designer for making the simplest radio station for the 50 MHz band with your own hands. This radio does NOT require any permission or callsign to operate. You need to collect two radio stations. The practical use of radio stations will allow you to understand some of the subtleties of setting up equipment and antennas, as well as the passage of radio waves. Walkie-talkies allow experiments to change or improve circuitry without serious risk of damage to the elements. The radio stations have a reserve for modernization, which will significantly increase the reliability and range of radio communications. The radios operate with amplitude modulation in half duplex mode. A real radio amateur is one who at least once in his life has assembled his own radio station!
