Do-it-yourself home theater repair

Often in home appliances fail power supplies. The mentioned group accounts for the lion's share of breakdowns, including home theater repair by itself. Developed two types of power supplies, - pulse and linear. Accordingly, it is customary to refer to transformers in the same way. The difference is that the linear ones are operating at a frequency of 50 Hz with a voltage of 220 V; for pulsed ones, using a transistor( or other key), a high-frequency sequence is formed. Due to the stroke it is possible to reduce the mass of the transformer, which favorably affects the demand. The information is known to the owner of the inverter welding machine, where the mains voltage is first rectified and then transformed as necessary for transmission through a pulse transformer. There is an opportunity to cook with alternating current, which is just great when it comes to non-ferrous metals, due to favorable temperature conditions.

A typical home theater device

Let's introduce the home theater device as a sophisticated DVD player, complete with a splitter for the Sound around channels, with external interface chips.

Approximate composition:

1. Power supply.
2. Laser Disk Reader.
3. The control panel on the buttons or touch.
4. Signal Amplifier for video and sound.
5. Splitter for Sound around.
6. External Interface Chipset.

The only information transfer protocol is usually easy to track. It breaks for a ridiculous reason: they stepped on a cable, pulled it out, by accident or on purpose. In the latter case, home theater repair is more concerned with the restoration of the mechanical part, the chips do not suffer from the brutal effects. With skillful hands, the situation is solved. More often in the circuit there is no food: the general supply with energy and local malfunctions. In the latter case, determining the location is easier than identifying the cause. A video is transmitted to Youtube, where the sound disappears when the diode overheats. Through the specified element fed amplifier chip, microcrack with increasing temperature increased in size, because of which the electrical contact was interrupted. When the freezer was applied to the diode, the performance of the home theater was restored.

Floating breakdowns are harder to track. There is a case when a pause was constantly appearing on the screen when watching a video, after which the playback was restored. As a result, it turned out that the fault was floating fault. The button had a breakdown in isolation, and the resistance constantly jumped on the contacts, which caused inadequate home theater behavior. Note, the keys are connected in series. It is difficult to indicate which one failed, even if it became clear that the problem was in the indicated place. The matter is aggravated by the fact that the buttons are extremely hard to remove without spoiling. Sometimes the conductive layer burns. In this context, a hair dryer is more appropriate than a soldering iron. Microbuttons are checked in the standard way, in the open state, the resistance is not less than 20 MΩ.

Going deep into the bowels of a home theater, make sure that the panel is in good condition. If an important function does not work, duplicate from the control panel, this will help to avoid unnecessary trouble. Home theater repair is brewing - one cannot do without knowledge of the device of power supplies.

Pulse and Linear Power Supply Units

In pursuit of lowering weight and size indicators and prices, smart manufacturers are adopting the technology of switching power supplies. The electronic filling of the switching heart of the cinema consists of microcircuits with the impossibility of repairing it.

Linear Power Supplies for Home Theaters

Considering the application for home theaters, we start with line power supplies that hold power and satellites of cheap DVD players perfectly. Initially, I ask - what breaks. The answer is simple! Internal Content:

1. Input Filter.
2. Transformer.
3. Diode Bridge.
4. Intermediate Filters.
5. Keys( relays, transistors).
6. Output Filters.
7. Output matching stages.

Often, instead of a fuse in a smart device, a low-power low-resistance resistor or a trivial wire is placed. When repairing a Sony home theater, please note:

• The fuse has a small resistance; if an X event occurs, the current begins to grow rapidly, and while the thread in the glass flask burns, the equipment will already suffer severely. The resistor immediately limits the current to nominal, acting as protection for the rest of the circuit. There were no serious studies, but according to the signs, such a scheme for a home theater is more appropriate than a standard fuse.

Typical components are found in the power supply: varistors and thermistors. The first and second are also intended to protect( not the fact that work).For example, varistors often short circuit fuse. From the above, we will take out:

• The fuse is replaced with a resistor of a suitable rating with the required dissipated power. How to find: read what is written on the fuse. The voltage level and current are applied to the case with ink, therefore, power is easily determined. The resistor should be blown at the same parameters. The power on the body does not always indicate the allowable( power dissipation, while the element is not yet lit).It is helpful to find the full resistor specification.

The fuse fails for two reasons:

1. Power surge.
2. Failure of part of the electrical circuit of the home theater.

From this point of view, there is a useful technique for switching power supplies: they put a light bulb instead of a blown fuse. If the light is on when the equipment is turned on, rather pull out the plug and look for a breakdown further. This is true only for switching power supplies for home theaters. In multicookers, for example, often a low-resistance resistor or fuse is in the heat circuit, which is not related to the rest of the electronics. It is clear, if the element is burned, there are two options:

1. Closed the spiral on the case.
2. TEN burned out, giving a short circuit.

The latter is unlikely, but it happens.

How to look for damage on the power supply board. It should start with capacitors, none is ringing in any direction. If a swollen keg is found, repairing the home theater will be a simple task. Locate the new capacitor in capacitance and breakdown voltage, replace it. If visual inspection shows that everything is in order, the home theater is likely to be ready for operation. Before turning on, ring the diodes from the bridge, everyone should in one direction give a short circuit. Then comes the turn of the key transistor or relay.

Transformers for linear power supplies

In a linear toroidal transformer, a thermal fuse is sometimes inserted between turns. In this case, the rating of the actuation and the word Fuse are often indicated on the sheath. An emergency situation causes a break in the primary winding. This is easily checked by the tester, do not forget that the input filter resistor is often in parallel, therefore the transformer is soldered from the circuit for testing. However, the first sign of a break is a large resistance plug. If more than 100 ohms can be traced, probably 90% of the case is in the breakage of the primary winding. By the way, a thermal fuse burns, just like a standard one, with power surges, you should not think that the breakdown occurred because the voltage surge burned the wire.

You do not need to immediately throw out the transformer, you will find a thickening under the sheath, you will understand that the sought is hidden here. We open the sheath, under a layer of coils we find a thermal fuse, replace it with a piece of wire or with a purchased element with similar characteristics( recall that the numbers are inscribed on the cambric or casing).If the only malfunction found is found, home theater repair will allow the equipment itself to serve an extra couple of years.

Switching Power Supplies for Home Theaters

Pulse power supply is different from the linear - the transformer is loaded with high-frequency current. This significantly reduces the size and weight while maintaining a large power delivered to the load. The inverter generates pulses with a frequency of tens of kHz to the welder, something similar happens in home theaters. However, there is no variation without needing to regulate power. In this case, the pulse repetition rate is constant. The generator on the chip controls the base of the transistor working on the primary winding. In this case, there are varistors and other interesting components inside. For example, thermistors increase the resistance with increasing temperature, which reduces the current and protects other elements from failure.

Often in the switching power supply units of home theaters the key elements of the circuit fail: thyristors, transistors, relays. The specified class of power sources was considered, details are missing.