How to rebuild the sound in a VCR to our standard. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Телевидение

 Comments on the article

It is not uncommon now to sell (at a price 2-3 times lower than new) in the markets of used video recorders, imported, in particular, from Germany. The main problem that the inexperienced consumer faces is that such VCRs are not able to play sound on our TVs (meaning when connected through the high-frequency input on the TV). The fact is that in Germany the frequency of the sound subcarrier is 5.5 MHz, while in our country it is 6.5 MHz. If you are the owner of such a device and understand which side to hold the soldering iron on, you can change the sound yourself.

First you need to find where the high-frequency converter is located - naturally, it is located where the RF cable (RF Out) is plugged in, therefore, I think there will be no problems with this.

Method one (the easiest)

Without opening the converter, try to gently twist the core of the coil responsible for the frequency of the audio subcarrier. Usually there are two coils on the converter - one is responsible for tuning to a television channel and one for the audio subcarrier. Opposite the channel tuning loop, there is usually a hole on the back of the device and a corresponding inscription (for example, 21-49 Ch), indicating in what limit the video signal frequency can be tuned. Thus, the remaining circuit is the culprit for the lack of sound. Moreover, it is the only one similar to the contours familiar to our eyes. Therefore, you should try to twist its core.

This method does not guarantee that you will immediately be able to rebuild the VCR, but nevertheless it is worth a try, since in my practice there were two such cases when it was possible.

Method two (a little harder)

If the advice described above did not help in any way, then we proceed to the second part of the plan for "Russification" of our apparatus. Usually, ferromagnets are used as cores for circuit coils, i.e. carbonyl iron or ferrite. Ferromagnets, as is known, lower the circuit frequency, while diamagnets increase it. Thus, if you carefully unscrew the native core and screw in a suitable brass or copper screw in its place, you can tune in to receive sound.

Method three (soldering)

If the second method did not meet your expectations, then you will have to attach a soldering iron to the whole thing. First you need to decide how the converter is electrically mated with the backplane of the VCR itself. Most often, unfortunately, the converter is soldered directly to the backplane, so you have to carefully unsolder it. To do this, I use a 60-watt soldering iron: fill all the contacts of the converter with low-melting solder, gently heat all the contacts evenly and try to pull out the converter module without undue effort. Then we remove excess solder with a braid and free up the mounting holes. If the converter itself communicates with the backplane via a detachable connection, then consider that you are very lucky, and you can not turn on the soldering iron for now.

Carefully remove the converter covers, screw the coil core back in and try to find the audio subcarrier circuit capacitor. The capacitor itself is usually soldered in parallel with the coil, so finding it is not difficult, but you need to make sure once again that this is the right capacitor. If the tape recorder is relatively old, then the converter is most likely made on discrete elements, and therefore the capacitor there looks in the usual way. If there is a chip there and the installation is done using surface mount elements, then you can proceed to the next step. Suppose you are lucky and the capacitor looks like a normal capacitor, unsolder it and read its value. Further, using the formula L \u836d 599 / C [pF], we find the inductance of the coil [mH], then, based on the found inductance, we determine the capacitance of the new capacitor using the formula C [pF] \u1d 1/3 [mH]. If the calculated capacitance value is not in the series of capacitors, then it can be made up of two or three connected in series or in parallel, in practice it is usually taken 9500-31 pF less than the calculated value. For example, in the AKAI-VS33 EG VCR, the native capacitor C23 was 2 pF in the circuit. The calculation showed that it is necessary to replace it with a capacitor with a capacity of 47 pF, leaving 39 pF for the parasitic capacitance of the installation. I put a composite capacitor of two connected in series (XNUMX pF and XNUMX pF).

After that, you can carefully lightly solder the converter unit in place and try to tune it by rotating the core to the desired sound subcarrier. After completing the setup, you need to insert the screens into place and boldly solder the converter as a whole (if it was soldered).

The situation is somewhat more difficult with tape recorders of the last years of production, since there the installation is carried out on the surface of the printed circuit board. Part marking is often absent as such, and the converter itself is assembled on a single chip, which is also sometimes unmarked. The installation is tight, so there is a chance of damaging it (especially if a drop of solder breaks off the soldering iron tip). As before, it is necessary to build on the contour. Usually there the circuit looks something like this (see fig.).

Sometimes it is enough to unsolder the capacitor C2, and you can achieve the appearance of a sound by restructuring the inductance of the coil, and if this does not work, then it is necessary to solder the capacitor C1 and in its place solder a 10 pF / 490 pF variable capacitor with a capacitance from a pocket receiver and rotating its axis catch the soundtrack. Based on the plate overlap sector, determine the approximate capacitance needed to replace the capacitor.

If, as a result of your tuning and restructuring efforts, you managed to smash the circuit to smithereens, do not despair - just find a 10.7 MHz circuit, recalculate it to 6.5 MHz and build it into a converter (or take a 6.5 MHz circuit from some TV that you have not repaired, then and you don't have to count).

I deliberately do not give any references to microcircuits and other parameters of the elements, I myself have not seen a single converter circuit except in [1], even in the native descriptions of tape recorders, converter circuits are represented by a rectangle with the inscription "RF converter".

Literature

1. Radio amateur. No. 1 1991 p.4-5
2. Reference book of a radio amateur designer. Moscow. Radio and communications, 1990, edited by N.I. Chistyakova, p. 18-19.

Author: Oleg Agarkov, Khmelnitsky; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Телевидение.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive A battery powered by hemoglobin has been developed 10.02.2024 Scientists at the University of Cordoba in Spain have developed a prototype battery that runs on hemoglobin, a key component of red blood cells. The new device is capable of operating for 20-30 days, providing a promising alternative to lithium-ion batteries. The development of a hemoglobin-based battery represents a significant step in the development of bioengineering and energy. This innovative solution opens up the prospect of creating more sustainable and environmentally friendly energy sources suitable for various fields, including medicine and electronics. Zinc-air batteries are one of the more environmentally friendly options compared to the commonly used lithium-ion batteries. They work through an oxygen reduction reaction involving zinc oxidation at the anode and oxygen reduction at the cathode. Scientists have turned their attention to hemoglobin as a potentially effective catalyst for this reaction. Hemoglobin, the protein responsible for transporting oxygen in the body, has unique properties necessary to catalyze the chemical reaction in the battery. The prototype battery demonstrated impressive performance, capable of maintaining functionality for several weeks with just 0,165 mg of hemoglobin. This opens up the prospect of using similar batteries in implantable medical devices such as pacemakers due to their biocompatibility and similarity to conditions in the body. However, several technical limitations need to be addressed before industrial application. In particular, it is necessary to search for a protein that can ensure the regeneration of oxygen and resume the reaction, as well as the development of methods for recharging the battery. It is also worth considering that the use of oxygen-based batteries may be limited in space applications.

Other interesting news:

▪ Integration of smoke detectors into computers and mobile devices

▪ Thread - 8500 years

▪ Graphene becomes a superconductor

▪ space mission to save the planet

▪ Smart surveillance camera with tracking function

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Amateur Radio Technologies. Selection of articles

▪ article Put a pig in. Popular expression

▪ Article What sports are considered Olympic? Detailed answer

▪ Derez's article is bearded. Legends, cultivation, methods of application

▪ article Subwoofer for a car. Part 1. Encyclopedia of radio electronics and electrical engineering

▪ article Intelligent charger for Ni-Cd batteries. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024