Choosing for a long time among chic in its own way, for use or, you have the right to hope for a high quality product. It is understood that not only the "assembly" of the device will be good, but also the clear sound. But the practice of operation shows that malfunctions of walkie-talkies periodically take place.
Since the cost of portable radios can be quite high, if you try to perform repairs yourself, it can be dangerous for them to completely fail. Why? Because almost all radio components are produced not only in the country of origin of the equipment, but can also be imported from other countries. Therefore, in the "local" conditions, it is almost impossible to find a replacement for an imported part.
Repair of portable radios should be carried out in special workshops. For example, if you decide to purchase a walkie-talkie in the Forter online store, its consultants will definitely tell you the addresses of official or licensed repair shops. They can perform both warranty and post-warranty repairs. idle walkie-talkie.
How do the masters “fight” with the malfunctions of your device? First of all, testing is carried out using a special stand and software. So they successfully deal with determining the reason why the radio does not work. After eliminating and replacing the non-working part/unit, the specialist will configure and program the device. Individual requests of the owner will also be taken into account - changing the radio frequency, power of the equipment.
Radio malfunctions many problems can be named. Their list is roughly as follows:
- background buzz in dynamics;
- the device does not turn on at all;
- failure of the transmitter module;
- no receiving signal.
The traditional recipes for the “treatment” of the first point are checking the antenna connection (the quality of the contacts, the applicability of the antenna for this model, etc.), installing a power filter (especially true for car radios), shielding the power wires with a ferrite ring, etc.
The reason for not turning on the device often lies in the fact that the contacts are reversed when connected - “+” and “-” are reversed. An idle transmission module - and now you already hear the air, but you cannot transmit anything to it. It is treated by replacing the output stage. You can list a number of other malfunctions, in addition, the consideration of problems due to mechanical damage is postponed.
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How to fix a radio station?
First of all, you need to remember that repair and adjustment cannot be combined. It is not recommended to twist the contours, trimmers and other trimmers in any case.
Basically, all malfunctions of radio stations can be divided into four main groups.
- The radio station does not turn on.
- The radio turns on but does not work.
- "Can't Hear Me" and
- "I can't hear anyone"
Then there are complex defects, somehow - the radio station hisses all the time (the squelch does not close), poor speech intelligibility, distortion during reception and transmission, and the like - but these defects will not be dealt with in this article.
The radio does not turn on
if the radio is turned on by the switch, then you need to check if it works. If with a button, then you need to immediately look for a power stabilizer chip. Stabilizers mainly produce a voltage of 5 or 9 volts. If there is no voltage at the output of the stabilizer, but there is voltage at the input, it most likely needs to be replaced.
If there is no voltage at the input of the stabilizer, then most likely the malfunction should be sought in the burned-out metallization layer, through which the supply voltage is supplied to the input of the voltage stabilizer.
But when connecting a radio station with the wrong polarity, you need to replace the protective diode, fuse, and sometimes restore the metallization.
Next, you need to check if the crystal oscillator of the radio processor is working. Sometimes a faulty quartz is the cause of this defect, but more often than not, a failed trimmer capacitor next to the quartz is the cause.
The radio turns on but does not work.
- in car radio First, change the PTT to a known good one. Through it, the signal also enters the loudspeaker of the radio station (for SI-BI radio stations), it also gives the command to transmit, it also switches the microphone to the input of the radio station's modulation amplifier. And, as a rule, it is the cause of many defects.
- antenna - both for portable and car radios - is not an ornament, but an essential element for good and high-quality communication. A very large part of the defects of the type - "the radio station does not work" ends with the repair of the antenna.
- in portable radio you need to see what frequency you are working on. It happens that attempts to communicate on different frequencies are the reason that the radio is brought in for repair. At the same time, sometimes the radio stations are deprogrammed, and if the channel numbers match, they try to work at different frequencies.
- it is recommended to check the battery charge, which is sometimes enough to turn on the radio, but alas, not enough to power the radio even at reception.
"Do not you hear me"
Basically, it all starts with a faulty antenna. Sometimes, if this is quickly discovered, then the owner of the radio station gets off only with its repair, and if not, then you have to change the output transistor.
It’s easier, of course, if everything rests on a broken PTT wire or on a faulty microphone. Again, first of all, you need to replace the PTT with a known good one.
There were cases that the radio station did not work in AM mode, but worked perfectly in FM, and this was due to a faulty transformer at the output of the UZCH microcircuit. Naturally, on the track where everyone works in AM, only the carrier was broadcast from this radio station.
First you need to check the power supply to the output transistors of the radio station. At the same time, it should be taken into account that the power must always be there, it goes there directly, without any switching. Then check the signal level at the base (output gate) - there should be a volt that way with a 5 RF signal. On the collector (drain) of the output volts from 12. If there is a signal at the input, but not at the output, change the output (voltages are indicated for a car radio station). For a portable one and a half times less.
At the same time, you need to know that one RF signal at the input is not enough for a field-effect transistor, in order for the transistor to work, a bias voltage must also be applied to the gate - from 3 to 5 Volts - it is with this voltage that the output power of the radio station is regulated.
"I can't hear anyone"
First of all, you need to restore the last steps before the appearance of this malfunction - did you drop it on the floor, or maybe you connected a DVR to the car, which works fine, but it also happens that it completely crushes the sensitivity of the radio station.
If you dropped it, then you can safely change the IF filter (black cube) - usually if it malfunctions at the radio station, you have to unscrew the noise suppressor knob almost to the limit in order to close the noise.
Sometimes, the speaker fails, but this is easy to find out by connecting an external speaker for a car radio and a headset for a portable one - a malfunction of the PTT or oxidized contacts in the headset jack is also checked.
Conclusion
This article did not talk about complex defects such as a malfunction of the VCO, PLL, open circuits, excitation of output transistors and other defects, for the repair of which, it is necessary to use specialized equipment, but nevertheless the author hopes that the above will help to cope with simple defects who are accustomed to do everything with their own hands.
This question is often asked by inaccurate users of technology. civilian range. 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, at the next polarity reversal, 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.
Vertex and Yaesu radios
We are witnessing the rapid development of radio electronics and radio electronic means of communication. Technology leadership in this area is a key success factor for YAESU. An example of communication technology are radio stations manufactured by the Japanese company Vertex Standard. Impeccable communication quality, ease of use, the possibility of concealed wearing using special headsets, work on one frequency channel using built-in CTCSS and DCS encoders / decoders allows you to work without interference for radio stations operating on the same channel, which is a significant advantage in cities with very high frequency division. There is a possibility of analog and digital coding of the speech signal of the communication channel for special services. Additional features on Vertex Standard radios include: Time Out Timer (TOT), Automatic Power Off (APO), Automatic Repeater Shift (ARS), Automatic Station Identification System (ARTS) to determine if you are within range of other radios, equipped with the same system. A special noise reduction system allows the user to set the squelch opening threshold according to the S-meter readings. The use of light metal alloys and durable plastic housings, a successful technical design solution, the use of a minimum number of controls with an optimal number of functions make the radio efficient and reliable in use.
This is only a general, incomplete description of the functionality inherent in different models of radio stations, and the more complex the radio station, the greater the capabilities it has. The design of modern radio stations based on 3, 4-layer printed circuit boards using SMD components and microprocessor technology reveals the great possibilities of such communication technology. Exposure to atmospheric and climatic influences, harsh technical operating conditions, non-compliance with technical requirements, and sometimes incompetence lead to various damage and malfunctions of radio stations. A feature of detecting malfunctions that occur in radio stations (as well as in other radio engineering, radio electronic devices) is the control of the output parameters of microcircuits, radio electronic components, nodes that form and convert certain signals of radio stations, control of CPU supply voltages, power stabilizers that feed these nodes, malfunction of electronic keys and the integrity of the circuits switched by the keys, the serviceability of the DATA bus circuits. These are the general directions for troubleshooting. Turning to specific models of radio stations, and in particular wearable ones, I would like to recall that the main causes of malfunctions arise due to their harsh operation.
The breakdown of the output transistor of the radio transmitter occurs, as a rule, for several reasons:
- Turning on the transmitter during battery charging, i.e. during surges in the power supply to the radio station.
- Long, unnecessarily, keeping the radio station on the transmission.
- Long transmission without an antenna or with a defective antenna.
- Reversal of the supply voltage.
With significant drops in the supply voltage, a breakdown of the protective zener diode connected in parallel with the supply voltage circuit occurs, both for portable radio stations and mobile base stations, as well as a breakdown of low-voltage stabilizers + 3V and + 5V, a failure of the energy-intensive CPU EEPROM memory. In some cases, an energy-intensive memory chip becomes faulty due to internal breakdowns of semiconductors.
The reason for the malfunction of this microcircuit is as follows:
- when the transmission is turned on, a three-time BEEP signal is heard in the speaker. the sensitivity of the receiver is underestimated, due to the fact that the central processor gave the wrong potential of the constant control voltage to the varicaps of the buffer bandpass filter.
- errors of digital data in the cells of the energy-intensive memory of the CPU lead to abnormal operation of the radio station and a discrepancy between its parameters and technical specifications. In this case, you need to either reprogram the CPU memory or replace it with a new one.
Quartz and ceramic filters are used in the receiver path when forming the signal of the first and second intermediate frequencies.
The causes of failure of these filters can be divided into two categories:
1. Internal mechanical damage, a crack appears in the receiver when tapping on the filter.
2. Deterioration of the quality factor of the filter, attenuation of the intermediate frequency signal when passing through the filter -30 dB or more.
In both cases, the filters must be replaced. It should also be noted here that there are reasons of the following nature: Open circuit between the outputs of the microcircuit of the amplifier of the limiter and the shaper of the second intermediate frequency (TA31136FN) and the conductors connecting it to the filter. In some models of radio stations, there are malfunctions in circuits where there are high-frequency SMD capacitors. The reason is as follows, a microcrack appears between the contact plate and the capacitor case. If you heat up such a capacitor with a soldering iron, the contact plate is soldered from the case. A similar reason occurs in the RC filter circuit of the noise amplifier, which is part of the second intermediate frequency driver chip. In this case, the radio station does not turn off the noise. There is another reason why the radio station does not respond to the noise suppressor is a violation of the soldering of the contacts of the ceramic discriminator included in the noise amplifier circuit. In very rare cases, the discriminator fails. As mentioned above, due to the harsh operation of portable radios (strong mechanical shocks), there is a violation of the contact between the quartz crystal and its holder of the master clock generator of the central processor, in some cases the quartz resonator is torn off the main board. When forming the frequency range in Vertex Standard radios, a programmable frequency synthesizer is used, controlled by the central processor via the DATA bus. The malfunctions that occur in this node are of the following nature: Mismatch between the set parameters of the transmitter frequency and the frequency of the first local oscillator, in some cases the absence of one of the signals.
The troubleshooting features of this node are as follows:
1. checking the integrity of the control circuits of the digital DATA bus from the central processor to the synthesizer
2. correspondence of the frequency parameters of the master oscillator of the synthesizer.
3. integrity and serviceability of the varicap.
The central processors, as a rule, work well for all Vertex Standard radio stations, maintain high stability of the set parameters and high speed of their processing, have protection for control circuits, control of the battery supply voltage or the on-board supply network for mobile base radio stations and when the supply voltage drops below critical level is automatically disconnected from it. The high reliability of the processors of radio stations from YAESU was noted. They very rarely go out of business. Only in those cases when the influencing factors greatly exceed the degree of protection, especially for those models in which the control circuits go to the external connectors of the radio stations and have a galvanic connection with the processor, that is, when high-voltage pulses enter these circuits. The VX-2R has a fault feature that is broken jumper contacts between the SW UNIT panel and the MAIN UNIT. When moisture gets on the MAIN UNIT board, as for all radio stations, a number of malfunctions occur, among the first are the reprogramming of the energy-intensive memory of the central processor, the breakdown of low-voltage voltage stabilizers + 3V + 5V and, as a rule, multiple breaks in conductors and transitional contacts of multilayer printed wiring. If the radio station is not dried in time, then the oxides will gradually corrode the conductors and transitions until the radio station is completely unrepairable. This applies to all radio models. Especially often wearable radio stations are exposed to this, with a sharp change in temperature in winter. To avoid these unwanted malfunctions, the radio station must be dried well with hot air, a hair dryer. Mobile base radios have their own fault characteristics. Starting with the power circuits, you should pay attention to the health of the protective zener diode, the "role" of which is performed by P6KA18. If the radio station is powered by the car's on-board network, then, as we know, impulses arise in this network high voltage, from electronic switches and the ignition coil, from poor contact in the starter release mechanism, when starting the engine, etc. The breakdown of this zener diode also occurs when an erroneous polarity reversal occurs when a radio station is connected. The VX-3000 radios have a control circuit output that connects to external J1004 and MIC UNIT connectors. These circuits have a galvanic connection with the central processors and audio processors, and although they are protected from static voltage by diode arrays connected between the circuit and the radio case, a breakdown still occurs at very high voltage pulses, most often the audio processor.
The reasons for this are as follows:
1. No deviation, because The audio processor contains stages for amplification, compression, and automatic gain control of the signal coming from the microphone.
2. The absence of a signal in the path of the preliminary ULF receiver.
3. Indication of two channels at the same time on the front panel of the radio is a sign of a fatal problem with the CPU.
The reasons for changing the output stages of transmitters are as follows:
- There is no radio emission in the antenna, and, as a rule, a small radius of radio traffic.
- Weak current when the transmitter is turned on
The peculiarity of replacing the output stage in VX-2000 radios is such that the manufacturer VERTEX STANDARD changed the output stage switching circuit and replaced the M 57741 microassembly with the RA30H1317 microassembly. This microassembly has a large gain and better dynamic performance, and in this regard, the following cascades were excluded from the circuit:
Q1014
Q1015
Scheme of automatic adjustment of the supply voltage of the first stage, microassembly M57741. The pre-terminal stage of the Q1018 transmitter, which is the buffer stage of this microassembly, is excluded. When replacing the VX-2000 output stage, the power must be adjusted and set according to the technical data Hi 25W and Lo 5W, respectively, potentiometers VR1002 and VR 1003. For VX-2500 radios, this is done by software. All radios of the latest release are programmed latest version software, and arrive at our company no later than 30 days from the date of issue. Replacing the output stage on the VXR-9000 requires a more thorough approach. During a long transmission, especially if the repeater is used in trunked networks, drains field effect transistors output stage are heated to the melting temperature of the solder. Therefore, when replacing transistors, it is necessary to change the usual refractory solder, after carefully removing the old one. It should be noted that the surface of the source and the contact plate, between the source and the heatsink, have a high grade of processing, because. the source is one of the three electrodes of the transistor and has a galvanic connection with the minus of the power source (case), through which a current of about 8 amperes flows, no heat-conducting paste is applied in this place. The most complex in their multifunctional capabilities and circuitry are amateur radio transceivers. The input power circuits are reliably protected, which does not entail serious consequences even if the supply voltage is reversed (the radio simply does not turn on). In the event of a breakdown of the protective zener diode, a command will not be received to turn on the supply voltage to the transceiver circuit. It also controls the reduction of the supply voltage by the central processor. There were cases when the electronic keys for turning on the transceiver were broken by the input voltage, these are Q3040, Q3007, Q3005, but when they were replaced, the transceiver's performance was restored. The reason for the sharp deterioration in sensitivity of the FT-897 receiver, FT-857, in most cases was due to current leakage through transistor Q 3027 (turning on TX), which closes the receiver input circuit to the body through diode D3018 when the transmitter is turned on. This is due to the ingress of high-voltage electromagnetic pulses (lightning discharges) into the input part of the receiver through the antenna connector.