Why did not turn on the TV.We will answer with a question! Thought why the majority of sensors of old household appliances are mechanical? Today, irons, electric kettles, oil heaters, washing machines, refrigerators often do without complex electronics. Nature, through the human mind, created a lot of sensors. It is known: pressure depends on temperature - the principle of operation of thermostats of refrigerators. Notice, everywhere they are trying to do with a voltage of 230 V. One phase at each house in the outlet. Sophisticated electronics requires careful treatment. Wondering why the TV does not turn on? Start learning about switching power supplies.
The reason for the silence of the TV
Verify the integrity of the Internet. Today, TVs at night update the software. Avoid interfering with the process. Change better while downloading updates.
TV contains a lot of electronics, for several reasons the stuffing is unable to be powered by 230 volts AC.For reasons of size, features of the lamp require a voltage of 6.3 volts( sometimes AC: magnetron microwave ovens).Applies to other electrodes, pn junctions of semiconductor devices. These elements do not withstand large currents due to their small size, limited power dissipation. Each TV starts with a switching power supply.
The adjective indicates the mode of operation of the transformer. The first televisions are devoid of impulses. The windings are formed by solid wire, the steel core of the transformer was the lion's share of the weight. Imagine the hulk crammed into a modern LCD monitor. Decreased other chips. The step is possible with a further decrease in the supply voltage. To reduce currents by reducing power dissipation. Above the processors there were the same manipulations, the increase in the number of transistors lifted the current consumption, making it incredibly large, the brain of the computer consumed more "Ilyich bulb".
So, the use of switching power supplies is justified. In most half a dozen secondary windings, the normal operation of electronics requires a number of nominal values. Remember the system unit of a personal computer.
Consider the principle of operation of pulsed power supplies.
Switching power supplies for TVs
The switching power supply starts a filter that protects the stuffing from external voltage surges. The safety measure device saves in part, there are other elements of protection. Varistor, at the input of the pulse generator power supply, closing the surge voltage to the case. Following the filter is rectifier. More often the bridge formed by four diodes is easily distinguishable against the background of other components. Some boards on the reverse, front side are marked with circuit icons( a triangle with a cross bar on top).This is followed by a well-defined force element. Any key:
The main thing is to have a control electrode. The power element is easy to find: it has a massive radiator. This is exactly the case when the electronics work at 230 volts. For this reason, the key element is expensive, massive and durable. It is clear now that the TV is not so assembled. There is one microcircuit fed( albeit via a zener diode) by the input potential difference. Pulse generator, using a key, cutting a rectified voltage of 50 Hz with a high frequency sequence. A thoughtful step can reduce the size of the transformer.
pulse power supply circuit. At the input of the pulse generator there is a zener diode that forms the supply voltage, a varistor, shorted to ground. The front of the voltage comes, closes the protective element. As a result, the varistor may burn like another component. The key is followed by a transformer, each winding of which must be called up. For example, a loop is sometimes left for feedback from the pulse generator. Ratings discussed above. For each individual winding.
Output is generated by Schottky diodes. Used for a unique quality - a small voltage drop of the open pn junction. Dissipated power is reduced. The output low-pass filter will smooth out the remaining ripple. The simplest is represented by a capacitor. Beginners are interested in the reason for the need to rectify the voltage twice. .. Direct current does not pass through the transformer. The microcircuit by means of a key cuts a sequence of pulses causing a response from the other side. The outlines of the signals are similar. Therefore, the voltage must be rectified. Lower windings. Voltage is much less than 230 volts. We will discuss how to fix the TV.
Repair of the
switching power supply unit It is not recommended to turn on the power supply unit of the faulty TV, since further progress of internal circuit damage is possible. If necessary, first check the fuse. Often in household appliances, the element is replaced by a piece of wire, not TVs. The fuse burns out when the circuit damage is already large. If burned out, do not rush to rejoice. Instead of a fuse, turn on a 150-watt Ilyich light bulb.
Now carefully turn on the power, unplug the power cord. The light will blink and go out. Burning, light means the need for further search for damage. Begin by visual inspection:
- Swollen capacitors. In the case of cylindrical electrolytic containers, the upper face is cut by a crosspiece. Sidewall bulging means: product needs to be replaced.
- Visually burnt items. Even if such a resistor does not burn out completely, it functions, it is better to replace it if there is a suitable one.
- Tracks: integrity, places of detachment. There is a poor-quality board installation.
- Prank the diode bridge. In the diagram, the direction of the current triangle indicates the opposite physical( Lincoln error is repeated).Charges flow from plus to minus. Consider the fact by choosing a polarity.
- Semiconductor devices call if you know how. Each concept transistor contains an arrow indicating a direction similar to a diode. Field-effect transistors with insulated gates will not ring, but the channel of low resistance in any direction. Designs are not listed, look at the place.
- The generator is broken if the key element is not heated. Although the diode circuit gives a high constant voltage.
Complement, some power supplies are equipped with protection against switching on without load. In this case, you need to load the lamp Ilyich. Line scanning works at a voltage of 130 volts, there will be a half-intensity. Elements can easily be replaced by equivalent ones. It is worth considering, the diodes and the key element in return are high-voltage( scientifically, powerful).
After eliminating the next malfunction, hold off the instrument. Try a light bulb, as shown above. If the light shines, the search should continue. Surely there is no circuit for a switching power supply. .. Look here: http: //telemaster.ru/shema/.Pretty good set. And on the example of the power supply unit based on the HB600 microassembly, everyone can look at all that they just talked about. Some nuances. In front of the bridge there are degaussing coils( Degaussing), and the input filter is implemented on one choke. One bridge diode is shunted by a capacitor in order to increase the service life of the device( when switched on, there is a sharp voltage surge, which is completely passed by the capacitor).
It can be seen that the generator chip is powered by a voltage of 8.5 V, taken from the main transformer. The power element is an npn transistor controlled by pulses through a small separate transformer. The primary winding circuit is isolated by three diodes connected in such a way that the positive half wave does not travel to earth until the key is open.
In the section, two schemes of television power supplies are given with examples of switching on the microassembly. On both we can see that, we believe, at the initial moment of time, the jump passes to the exit. Charges with one of the windings of the capacitor, which takes power from the pulse generator. As a result, the key is started and the power supply enters the working mode. Then the voltage of 8.5 V is constantly replenished through the same winding.
Now, knowing the scheme of operation of the switching power supply, the readers themselves will be able to list possible malfunctions. And having a tester and a circuit in your hands, you can certainly answer the question why the TV does not turn on, and what could break. On this we wish good luck to those wishing to master the repair of household appliances with their own hands and say goodbye exactly until the next time. The basis of any work is understanding. Knowing how the device works, anyone can do the repair. Moreover, pulse power supplies are found everywhere. Chargers, DC adapters, personal computer monitors.
Repair smart electronics, including controllers, is difficult. Developed technology "home" programming, ignored by Russians. Creation of complex devices, information readers, players of audio and video formats is available. On the knee will earn a million. Verily, verily I say.