Do-it-yourself radio repair

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Master Wink. All with your own hands! is a site for those who like to make, repair, create with their own hands! Here you will find free guides, programs.
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Many Chinese radios work in the kitchen, today we will tell you how to fix a very common breakdown with your own hands. This article will not open America to experienced radio amateurs, but it may well come in handy for beginners Samodelkin. Today we will talk about how to fix the most common breakdown - crackling during operation and volume control. It often happens that the receiver lives quietly and calmly, no one drops it, does not water it from the kettle, but it starts to make a terrible rattle when you try 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 worn groove in the glass-textolite base. The experimental exhibit we have is a very common cheap Chinese radio KIPO KB-308AC

So let's get started with the repair. 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 on the reverse side, an indicator plastic plastic is attached to one of the components (a variable capacitor), which runs around the scoreboard 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 that I spoke about above wiped with a slider in the resistive layer.

Now, with the help of a match, we apply lubricant without stint, here you can’t spoil the porridge with oil, you can fill the entire volume. Well, we collect in the reverse order.

Turn on and...he's still rattling! We turn off the receiver, turn the regulator from the extreme to the extreme position about 30 times and ... Voila, everything works! The volume is adjusted softly and smoothly, like on his own assembly line in the Chinese village 🙂!

I hope the article will be useful to someone, in my life I have repaired many receivers in this not tricky way.

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This question is often asked by inaccurate users of civilian range equipment. The problem occurs quite often and requires wide consecration. 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 civil band decide to install communication equipment in a car on their own. The problem is that due to 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. This blows the fuse located on the positive power cable. When you try to replace it with a spare, it also burns out. Particularly 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 sobers 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 cover 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, logically, 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 illustrations and photographs using the MegaJet MJ-600 walkie-talkie as an example. However, a similar method of protecting the station is used in 90% of radios and, having understood the principle, it is possible to easily repair this malfunction in other stations.

Let's take a look at the diagram. We are interested in the power circuit at the input of the radio station. We find the connector CN2, and next to it is the protective diode D20, marked as 1N4002.

As you can see, the diode is turned on so that during normal turn-on, the cathode to (+), the anode to (-) current does not flow through it. However, if we reverse the polarity, current will flow through the diode, and the current strength will be much higher than that for which it is designed.

Let's turn 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 greater than its nominal value 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 of this, the current in the circuit will exceed 3A and the fuse on the cable will already burn out. Naturally, replacing the fuse with a new one, without repair, will also burn out the new fuse.

What to do? You just need to replace the protective diode.

We open the radio station, for MegaJet MJ-600 you will have to remove both covers and find a protective diode on the board. As a rule, it is located near the junction of the power wires with the board.

It is necessary to unsolder the old diode from the board and in its place solder a similar one or one designed for a higher current, for example, 5-7A, in this case, the next time the polarity is reversed, the fuse will burn out before the diode and it will not be possible to climb inside the station.

Another protection option is not the parallel connection of the diode, but series, up to the filter capacitance.

In this case, it is best to use a Schottky diode with a current of 3-5A more than the station's peak consumption 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 hence the output power. If connected incorrectly, the radio simply will not turn on. Another bonus of such inclusion is a significant reduction in the "howl" from the engine generator, if any.

In your hands, dear reader, is the first book published in Russia on the repair of portable radio stations. Don't let her out of your hands.

The proposed book describes thirteen models of seven types of mass portable radio stations available on the markets of Russia and the CIS countries.

The principal 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 troubleshooting methods using the simplest available instruments.

The book is intended for a wide range of readers familiar with the basics of radio engineering: students of colleges, schools and schools of 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 users of wearable radios!

With your radio, acquired a long time ago or not, problems began:

¦ You hear, but no one answers your appeals: it seems that the transmitter of your radio station is out of order;

¦ You don’t hear anyone or anything: the receiver is out of order, although the transmitter may be in working order.

You are already thinking about purchasing a new radio station, and it can cost a lot of money. Don't rush, dear reader.

In this book, you will find detailed troubleshooting techniques that will help you get your radio back up and running at a cost far less than a new radio.

Please note that the purchase of a new radio station does not always guarantee getting rid of any problems, because there is practically no trouble-free 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 electrical circuit diagram;

¦ study the placement of devices according to the wiring drawing or wiring diagram in order to be well oriented in the location on the circuit board of functional units, devices and individual elements;

¦ have the necessary minimum of measuring instruments available and be able to use them;

¦ to have, finally, certain and necessary skills to perform installation work to replace radio elements, including large integrated circuits.

The first chapter of the proposed book gives a brief summary of the theoretical foundations of modern radio stations in general, and portable ones as well.The composition and constructive construction 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 following seven chapters describe the technical characteristics and construction of several models of seven types of portable (portable) radios; the order of search and elimination of possible malfunctions and methods of regulation (setting) of receiving and transmitting devices of all models of radio stations are given; finally, 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 work is given.

The first wearable radio stations - for 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 CIS countries are literally flooded with many 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 wearable radio users 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.

The proposed 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 and troubleshooting; methods of regulation of radio stations with the use of available instrumentation are given.

On the diagrams given in the book, the values ​​​​of capacitances in microfarads, resistors in ohms, and inductances in microhenry are given without letter designations.

This experience is for a beginner who has achieved 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 who knows that these are electronic components. At the same time, he has an enduring desire to bring "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 Okean-209 radio, perhaps even an old one. It is in good condition, but it is simply not possible to use it anymore. The reason - for example, not quite adequate sound reproduction. The first thing you need to learn and remember throughout the entire event is that you can’t master the repair “in one sitting”, so do everything thoroughly and during the repair, don’t really rely on your excellent memory, but take notes and even a photo of what will have to be done in its process. I started by searching the Internet for information, and in full, about the restored radio. This is an instruction manual, a diagram of the location of blocks and assemblies on the chassis of the radio receiver, a circuit diagram, wiring diagrams of printed circuit boards and a list of components and parts used in it.

After reading the instructions and studying the radio diagrams, I unscrewed the screws and removed the back cover, side case and front panel.

I didn’t burden myself with super-complex tasks, but simply, as most electronics luminaries advise, I decided to check the serviceability of electrolytic capacitors and variable resistors, to replace the unusable ones. To do this, I removed separate blocks 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 on each end. There will be two cards, 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 node. It can be seen from the circuit diagram that his transformer is designed to work with both 220 V and 127 V mains voltage. I did not catch the time when there were sockets with a voltage of 127 V, so this “feature” of power is perceived by me as an insidious legacy, from which needs to be disposed of

Having measured the resistance of the input windings of the transformer, he revealed the average tap for 127 V, bit off the bare end, wound it with a ring and isolated it. The presence and location of electronic components is especially clearly visible in the wiring diagram. There is only one electrolyte of interest to me here. I solder it, discharge it and measure the capacitance - 60 uF is not enough to the norm, 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 microfarads, slightly larger than what is missing, but for the same voltage - 25 V. Before installation, a new component must be checked for compliance with the capacitance, and ESR to a valid value. I did it, applied a mains voltage of 220 V to the PSU and measured the output received - everything is normal, the power supply is working.

Now the sound amplifier. Everything is more serious here.

I find seven K50-12 electrolytic capacitors on the board, well, very ancient in appearance. I move the wiring diagram closer to me and solder each container one leg from the board. Naturally, where possible. Where not, the capacitor is soldered completely.

You can completely solder everything, there is a montage, but it may not be, and then it will save a lot of time and save your nerves.

I checked the ESR with a probe. The one in the photo (91 millivolts) corresponds, according to the conversion table for this probe, to somewhere more than 30 ohms. According to the tolerance table, it can be seen that a capacitance close to 50 uF x 16 V has a limit of 1.3 ohms.

The rest, except for two, are about the same. They are not suitable for further use. For two electrolytes with a valid 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 cod in the dynamics when it was rotated. I connected an ohmmeter to it and, when it rotated, I saw a real “leapfrog” on the display, in some places the current-carrying track inside its case was erased. I put a serviceable identical variable resistor and assemble the amplifier board in its original position. Now check. The output is a suitable speaker, 9 V power supply 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 RF-IF node remained. He did not take it off, and there was no need. It had poorly-proven K50-12 electrolytic capacitors on it, 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, he turned on the radio receiver in the network. Everything worked and most importantly better than it was. And may all your work end in success, Babay.

Hello everyone, today I found a Chinese KIPO FM receiver in the attic, but what's the difference what it's called - they are almost all the same in design and layout. I assessed the condition by eye - everything seems to be buzzing, the mains plug was really torn off, I stripped the wires and into the outlet - silence. Yeah, we take it apart, we see everything is fine, and then it dawned on me that it had been buggy for a long time, the frequency was gone, the volume was disappearing, I wanted to repair it, but my hands didn’t reach, but no one knows how he ended up in the attic, or maybe I’ll remember. Let's move on - appearance.

We disassemble the receiver. First, let's remove the battery cover 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 a hole on the right side, unscrew the bolt and finally, remove the cover. Unsolder all the wires but remember where it was.

I began to think that it 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 donor of the resistor and capacitor.

Below in the photo, I already soldered a variable capacitor, and clamped the contacts of the variable resistor with tweezers. Hooray, the receiver came to life!

Since the getinax is very fragile, especially Chinese, the tracks are very difficult to tolerate heat, they instantly peel off, a little broke but soldered the variable resistor, and to be sure, I fixed it with hot glue, like this.

I forgot to say, the FM receiver is built on the popular SONY CX16918 chip with very good parameters, in the future I will make another radio receiver with an audio signal amplifier and the like on this chip - winter is still ahead.

The Alpinist 320 receiver was brought to me for repair with a complaint that the receiver did not catch anything but noise. But instead of a simple repair, 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 module supply voltage is limited to 7.5V, but it's better not to risk it, and power the board from 5-6V, and the receiver's power supply is 9V, a quick and hasty decision to use a roll. The internal antenna is ferrite and is not suitable for FM. I removed a telescopic antenna from another radio. And I purchased the variable resistors missing in the package without any problems, while leaving the volume control native, although according to the circuit the recommended resistance is 100K, but the voltage between the extreme terminals is 1.25v, and I used a variable resistor of 8K without any problems.
Here is the current look of the insides of the radio

But the decision to use the roll was hasty, we have a classic power supply on a single transistor, the only thing I needed to change was the zener diode, and with 9V I got 5V, there was no such zener diode, but there were two powerful ones at 2.7V, but due to the fall received 5.2 - 5.3V

Now we just pull out the old insides and instead of them we fix the board of the new receiver

We solder the power wires, adjustments ... Please note that we get the maximum frequency and volume by grounding the middle terminal of the variable resistors, and not by pulling it to the power source!
To facilitate the design, I removed all the unnecessary part of the board, leaving only the resistor fasteners. The antenna was soldered to a piece of textolite, which is screwed to the old board mount.

That's it, a new radio in the old building, the reception is confident and clear.

JLCPCB is the largest prototype PCB 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!

You can download movies, clips, episodes, trailers for free, and you do not need to visit the Youtube site itself.

Download and watch the ocean of endless videos in high quality. Everything is free and without registration!

Good afternoon. Today I want to describe the repair of a radio made in China. I am wary of any Chinese electronics. Because not a single Chinese product that came into my hands had the quality of at least a small C grade.
And so, we have a recently purchased radio. In operation was once in nature.
Complaints are as follows:
- Very poor reception (initially)
- The setting wheel does not spin well (constantly sticks) - this problem arose in the middle of the day of the first and last operation.
The product did not fall and did not drop, did not plunge into the water.

Let's start with visual analysis.

This is how the product arrived 🙂
It is immediately clear that there was contact with sand 🙂 We will fix this with a needle. Carefully clean each cell with a needle and shake the sand out of the speaker. Or even easier. Use an old dry toothbrush and brush slowly.
Next, we proceed to disassembly.

This is where the screw is hiding.

Another bad habit of Chinese craftsmen is to assemble plastic products with screws! Several disassemblies or miscalculation of strength and you need to screw in a screw of a slightly larger diameter.

Under the cover holding the batteries, there is another screw - we also carefully unscrew it.
Very carefully and extremely carefully open the receiver. Chinese masters are very fond of saving on everything and do not want to make detachable connections. Therefore, the wires connecting the nodes of the device are thin and their length is “stretch”. Therefore, in order not to cut off any wire and then not to look for where it fell off for a long time - do not use force!

Poor reception problem solved. As shown in the figure 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 "signet".

Carefully unscrew both screws holding the circuit board.

We solder the broken wire to the output of the RC circuit. The site is displayed on the side of the elements (in the figure it is indicated 1). The 2nd is a capacitor that forms a circuit with a coil, which is near the antenna wiring site (marked 1).

Reception will be! Now let's deal with the frequency adjustment wheel.
The first thought that came to me was that the time for an air condenser had come, without even starting! :) :) :)
But no. To my amazement, everything turned out to be even easier. It's just that the Chinese geniuses did not turn 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.

We assemble the receiver, insert the batteries and listen to the radio!

Thank you for your attention. Hope I helped someone.

A blog for beginner radio amateurs who want to make their first radio station with their own hands, 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 range with your own hands. This radio DOES NOT REQUIRE any permission or call sign to operate this radio. It is necessary to collect two radio stations. The practical application 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 you to conduct experiments to change or improve the circuit without a serious risk of damaging the elements. Radio stations have a reserve for modernization, which will significantly increase the reliability and range of radio communications. Radio stations operate with amplitude modulation in half-duplex mode. A real radio amateur is one who has assembled his own radio station at least once in his life!