How to disable the demagnetization loop on the TV. Demagnetization of the CRT. Posistor. You need to unscrew the back cover of the TV, slide out the board on which the radio components are located and find the plug for turning on the demagnetizing loop. As a rule, directly

Sometimes a magnetized tool is useful - for example a screwdriver, the screw will not come off from it. And when the file, tap, drill, pliers are magnetized - this is not very good, rather even very bad in terms of adhesion of metal filings and their subsequent removal. This article will discuss the topic of how you can make a demagnetizer with your own hands and from improvised means.

And so, let's go. To begin with, I will tell you about the demagnetizers, the components for which I managed to find in my stocks. At the end of the article, I will give a few more options for the demagnetizer.

A demagnetizer is essentially an electromagnet. If a constant voltage is applied to its coil, then a constant magnetic field will appear in it, and if an alternating one, an alternating field will appear, which will demagnetize the metal.

I took the CRT demagnetization loop:

I folded it once:

And folded it two:

As a result, we get a demagnetizer coil, which is already ready for use. But due to the small working area and strong heating, I connected one more loop in series:

In order not to burn the coil or forget to turn it off, we connect the whole thing through a button without latching and a fuse:

Such a coil is good for demagnetizing a large tool, but it will be inconvenient to use it to demagnetize drills and taps, so I made the second option - small and neat.

In this version, I used a solenoid from a baboon tape recorder, connected through a transformer.

How to use demagnetizers:

To demagnetize, you must apply to the coil AC voltage corresponding to the coil, then insert the part inside the solenoid and hold it there for a few seconds, then remove, without turning off the power.

Where to get the coil:

Almost any coil will do. The main rule to remember is that the coil must correspond to the voltage, for example, if we connect the solenoid from the tape recorder at ~ 220V, it will burn, and if we connect the device for demagnetizing the kinescope at ~ 12V, then there will be no effect. Usually the data is written on the coil itself, and if not, then we google the name.

You can use a transformer - disassemble the core, wind up the secondary, and connect the primary to the network. The effect will be the same. There are transformers wound on a ring - such modifications do not require.

The coil is included in the electromagnetic chime, the solenoid relay of the car starter. There are a lot of options ...

You can also wind the coil yourself. Here is the data: Solenoid frame 80 mm long. The inner diameter of the frame is 30-35 mm. Along the edges of the frame, cheeks with a diameter of 80 mm and a thickness of 5-6 mm. Solenoid winding - about 1000 turns of PEL or PEV wire with a diameter of 0.7-0.9 mm. The resistance of such a winding will be about 8 ohms. Such a coil is intended for a voltage of 10-15 volts.

The winding data of various electromagnets can be found on the net.

Conclusion from the above:

- We connect the coil designed for 220 volts directly to the network. A coil designed for 110 volts, for example, can be connected directly to the network, but only for a short time. We connect the coil designed for 12 volts through a transformer.

- We supply the coil with alternating voltage

- When demagnetizing, first remove the instrument from the coil, and only then turn off the power. Otherwise, the metal may not demagnetize.

Many owners of outdated TVs are wondering: how can you demagnetize a TV at home? People face this problem when the device starts to malfunction, showing a distorted picture. This problem is inherent in most devices with a cathode-ray tube and is called "magnetization".

The main reason for the magnetization of the kinescope is the long-term presence of electronic devices in the immediate vicinity of it. In modern homes, this situation is not uncommon: microwave ovens, computers and telephones are present in almost every apartment. It is not uncommon for a TV set to be put on the microwave without thinking about it, huh? If your machine has suffered from regular exposure to electromagnetic field- do not rush to carry it to the workshop. You can solve the problem yourself. Depending on how badly your TV is magnetized, you can fix it using one of two options:

• activate the built-in protection against magnetization;
• use a device called a choke.

Important: never use a permanent magnet to demagnetize the CRT.

We activate the built-in protection

Each CRT TV has in its arsenal built-in protection against screen magnetization - the so-called demagnetization loop. To activate it, it is enough to turn off the device for a while and let the loop do its job.

You need to know that this loop starts working only when the device is disconnected from the power supply. The thing is that when the power is on, the voltage is supplied to the posistor continuously, and it cannot limit the supply of energy to the demagnetization loop. In this case, the demagnetization system remains inactive. Experts recommend that you periodically disconnect the TV from the electrical outlet to prevent possible problems with a picture tube.

When choosing this option, it should be borne in mind that the loop cannot cope with the strong magnetization of the kinescope. In this case, you will have to resort to the second method.

Demagnetization with a choke

How to demagnetize a TV at home using a choke? First, you need to prepare the device for this process:

• disconnect the TV from the network;
• remove all electrical appliances from the place of demagnetization.

After the above steps, turn on the choke in the power supply network and begin to carry out circular movements in a spiral, bringing it closer to the center of the CRT. By performing such manipulations, move the choke away from the TV screen at a sufficient distance and turn off the device.

Important: the whole process of demagnetizing should not take you more than 40-50 seconds, otherwise you can harm the TV picture tube.

Homemade choke

How to make a choke at home

You can assemble an electric magnet at home using an electric wire with a plug, an iron arc and a winding.

Take iron arc and connect it to the electrical network by connecting with a 220V wire. Insulate the resulting device and connect it to the power supply. The sequence of actions is no different from the process of demagnetization with a special choke.

If you followed the instructions in the article exactly, but your TV viewing device still shows poor quality images, or, possible reason – kinescope shadow mask shift... This malfunction cannot be repaired, and the only solution to the problem is to buy a new picture tube or TV. Now there are many models on the market, and in order not to make a mistake when buying, you need to know. The optimal solution would be working on.

Hello everyone. An LG 21FU3RG-Z3 TV with spots on the screen was brought in for repair.

Such malfunctions are quite common, and the repair consists in replacing only one part, the so-called posistor.

I would like to stipulate at once one very significant nuance. Before starting the repair, be sure to ask the owner if the TV has fallen... It often happens that after a fall, the picture tube mask (a small mesh inside the picture tube) gets lost, which can never be restored, and all this is treated only by replacing the picture tube. In my case, there were no falls, so it can be repaired.

So, let's begin. Having disassembled the TV, I began to look for a posistor.

It is usually located next to the demagnetization loop connector. For reliability, I rang the loop with a tester, the result showed 5 ohms, which is within normal limits.

The posistor in this TV is used for 3 feet.

I usually buy 2-foot posistors, as it seems to me that they are universal, and I use them in all TVs.

Below is a diagram of a demagnetization loop with a 3-leg posistor.

To install a posistor on 2 legs, we connect it in series with the demagnetization loop as in the diagram, while not using one terminal.

Hello everyone!

Quite often, in the practice of repairing CRT TVs, there is such a malfunction as the appearance of color spots on the screen or seemingly unreasonable blown of the protective fuse.

Colored spots , mainly, are formed at the corners of the kinescope and do not appear at once, but within a certain time. It may seem that the manifestation of such a malfunction tells us about a failure. kinescope , but, I hasten to calm you down, kinescope here it is not to blame and is quite workable. Such a "spotted" image indicates demagnetizing or magnetizing screen our TV.

If the TV long time did not turn off from the network, but turned off using the remote control (was in standby mode), then the magnetization of the kinescope may occur. The fact is that in most CRT TVs, the demagnetization system starts working when the TV is turned on to the network, and if the device is constantly connected to the network, then demagnetization does not occur when the TV is turned on from the remote control.

The principle of the demagnetization system is as follows: when you turn on the "network" button on the TV, the voltage begins to flow to the posistor, which, in turn, feeds the demagnetization loop of the kinescope located on its band, i.e. on the back of the screen. When the TV is demagnetized, the PTC resistor limits the power supply to the loop. And so every time you turn on the TV to the network. And if your device is constantly in standby mode, i.e. turns on and off only from the remote control, then the power on posistor and the power supply is supplied continuously (this can be observed by looking at the LED on the TV panel) and the demagnetization system is constantly turned off. That is why it is recommended to disconnect the TV from the 220 V network at least once a week.

« Posistor- This is an ordinary thermistor, which changes resistance depending on temperature. In the cold state, the resistance of the posistor is very small (5 - 15 Ohm), in the heated state, more than 10 kOhm. The posistor is turned on directly into the TV power circuit in series with the demagnetization loop. When the TV is turned on to the network, the resistance of the posistor is small and current flows through it to the demagnetization loop. After heating, the PTC thermistor gives more resistance, which prevents the passage of voltage to the loop. By design, posistors may differ, but they are all interchangeable. "

Also, this malfunction may appear if the posistor itself fails. If you turned off and turned on your TV several times from the network, and the spots do not disappear, then this indicates a failure of the posistor, which should be replaced.

Another option in which the posistor may be guilty is when the mains fuse blows. In this case, the power supply is in good condition. In the posistor, in this case, when voltage is applied to it, a short circuit occurs and, accordingly, the entire voltage supply to the TV is short-circuited. As a result, the protective fuse blows out.

Replacement posistor

Replacing the posistor is not particularly difficult, as well as special knowledge.

Need to unscrew back cover TV, slide out the board on which the radio components are located and find the plug for the demagnetization loop. As a rule, a posistor is located directly next to this plug. The failed part must be soldered out and a new or known good one must be soldered into this place.

That, in fact, is all!

If you have any questions or have any suggestions and comments, you can state them in the comments.

Seal

Magnetized picture tube

Colored spots, stripes, colors are incorrect on the image, all these are signs that the picture tube mask has become magnetized. You can call the wizard, but this article is about how to demagnetize the kinescope yourself.

There are two reasons for the magnetization of the kinescope: a malfunction in the TV itself or it was exposed to an external magnetic field, for example from a nearby speaker system, a permanent magnet brought to the TV, as well as a magnetic field from devices such as a transformer stabilizer, or an uninterruptible power supply.

There are two options for demagnetizing the TV picture tube:

• with a small magnetization, the TV can handle itself, for this it has a demagnetization system. You just need to turn off the TV from the network and after waiting 10 - 15 minutes turn it on again. If the image is improved, the procedure can be repeated.
• if it was not possible to demagnetize, then it is necessary to buy, or better to borrow from friends, a choke for demagnetizing the kinescope. If you couldn't find it, then it doesn't matter either, you can do it yourself.

The principle on which demagnetization is based is a smoothly disappearing alternating magnetic field. During operation, do not make any sudden movements, otherwise this will lead to re-magnetization.

Once upon a time I used a factory choke, borrowed from a friend. Degaussing not so much TV picture tubes as tape recorders and he looked like this.

Today's TVs cope better with magnetization, I even forgot when I had to use a choke.
In order to make a choke for demagnetization, we take a 100 mm mandrel and wind 850 - 900 turns on it with a PEL-2 wire with a diameter of 0.15 mm and completely insulate it with insulating tape. To turn it on and off, we fix a button on the device, and a 220 V power cord.

To demagnetize the kinescope, do the following:

1. Turn on the TV and let it warm up for 10 minutes;
2. Having located at a distance of at least 2 meters, turn on the throttle and first with large circular movements, and then less and less without stopping the rotation, slowly approach the kinescope for 3 - 5 seconds. In this case, strong color distortions will begin to appear in the image;
3. After that, without stopping the rotation, we also slowly move back to the same place and turn off the throttle. After such an operation, the distortions should disappear. If not, then repeat the procedure again.

Remember: you cannot keep the choke on for a long time to prevent it from heating up. The entire operation should take about 30 seconds.