Colour television is a name relative to black and white television, and although it has been in our lives for decades now, we already have lcd tv and even smart tv, colour television is not completely out, and it still exists in some families. However, because of the delay in upgrading, families that use mostly general colour power have had long periods of use and there are some failures. I'm going to show you a few of the usual colored tv maintenance methods!
(i) current measurement
The current method is used primarily to determine whether the line output level has a flow failure and whether the line output transformer has a local short circuit. The maintenance is usually carried out at a point in the power supply circuit at the breakout output level, followed by a string of current tables at the breakout point according to the current flow. Figure 2 shows the currents of the currents measured at the line output level. The scale scale used is 2. 5 a in direct flow, and the measurements and questions described are as follows:
1. The currents greater than 50 ma at the time of measurement indicate severe penetration or short-circuit failure at the line output stage. It can be broadly judged as a result of local short circuits of line-out transformers, line-out truncheons, reverse-range contours, etc。
No electrical current, i. E., the static of the compass, which means that the line output level circuits measured are not operated or the line output tube is open。
3. Measurement of normal line output class working currents, typically 350-400 ma, indicates normal line output level and line oscillation level。
(ii) direct observation
“intangible” can be divided into “intangible” and “component intuitive”。
“intuitive” detection of malfunctions is performed using the “intangible” phenomenon, which begins with a classification of malfunctions, where we summarize the wide variety of malfunctions that occur in colour television into the following categories。
(1) “nothing”, i. E. Any manifestation of electricityless work on television. The failure may be short circuits or passings such as switch-off power, line scans, field scans, acoustic channels, etc. The remote control system is also considered for remote colour televisions。
(2) “nine”
That is, no raster (recipient colour televisions with no characters), no images, no acoustics, but with the reaction of a "creaking" or other power-added operation, the failure should be on a power switch or line scanning circuit。
(3) images and acoustics are normally non-facing in public corridors, adjusting units and, for remote colour televisions, taking into account remote control systems。
(4) images include: no images, poor image effects, colour bias of images, faults in video channels between image acoustic separation, adjustment units. Remote colour televisions may also occur in remote control systems。
(5) accompaniment includes a non-accompaniment, small accompaniment, poor accompaniment effects, malfunctions in the accompaniment channel after the image accompaniment is separated, and remote control systems are also considered for remote colour television。
(6) the raster consists of a non-radical raster, a small raster, a black background, a dark brightness, too brightness, a bright line, etc. The failure is usually in the scanning channel。
The range of failure maintenance is reduced through a “intuitive” approach to minor differences in similar failure phenomena. The failures of colour televisions vary widely, with tens of thousands of failures, which are classified as only six categories, and the determination of the area of failure is generally in that part. If we break down each of these types of malfunctions and take advantage of the small differences between different phenomena in the same type of failure, the range of failure maintenance can be further reduced, in some cases even to a specific component。
In colour televisions, the same element is damaged in different ways or to different degrees, and may cause different malfunctions. A sample magnification tube opening in a switch power source results in a high switch power output voltage; if punched, a switch power output output is low or no voltage output。
On the contrary, damage to different components of different unit circuits may sometimes cause the same failure. For example, “none” failure may be caused by power problems with switches or by problems with scanning circuits。
Therefore, the maintenance of colour televisions should be based on the correct classification of malfunctions in order to reduce them to one or more units of circuits, while at the same time identifying the characteristics of different malfunctions, thereby further reducing the failure to a unit circuit or a specific component. Several of the most common failures of colour televisions and corresponding failure elements are described here。
(1) the cathode is magnetic。
The raster and the image are partially coloured or have rainbow bands, and this failure is referred to as the magnetic of the catheter. The cause of the failure is the colored magnetic circuit. The solution is to directly replace the anti-magnetic resistance or the anti-magnetic loop。
(2) there are 1-low white lines (back-scanning lines) on the top of the raster。
The failure was due to the pump power circuit at the otl output level. The solution is 4. 7 μf, 10 μf, 100 μf, 220 μf voltage caps, isolation of diodes or field output thick membranes at the reversible output level。
(3) run。
When the key is pressed lightly, if there is a black bar interference on the raster, the key is replaced directly。
(4) poor effect of non-preset status images。
Closes the small door on the television panel, which opens the aft (ordinary colour television) or preset switch (controlled colour television), alters the image, directly reconciles or replaces the medium-week aft in the public channel with 38. O mhz。
(5) run, do not lock。
Regular colour television sets are easy to run, search stations are difficult to pull out effective images, remote colour television channels cannot lock their programmes, and the aft medium-week and 38. 0 mhz medium-weeks in public corridors should be replaced。
(6) a raster and image colour bias。
Distinguishing the cause of the failure: receiving a standard colour signal, closing the colour saturation and displaying a white-to-black ladder shift on the screen. (a) a dark balance adjuster at three equal distances on the board of view, if the low brightness vertical is coloured to indicate a dark balance; if the brighter verticals have some colour, which indicates that the light is not well balanced, they can be adjusted for two light-balanced devices that are more distant from the board。
The bright balance adjustment is collectively referred to as the white balance adjustment。
There are a few green or red noises in the black and white noise points of the raster, and the image colours are not correct, and two more distant bits of electrons should first be regulated on the panel。
Strong green rasters with strong red rasters, strong blue rasters with white backsweeps in the raster shall first check the discharge gap or triode between the corresponding cathodes of the cvd。
(7) there are only tilted black and white bars on the screen。
This failure is called an incorrect frequency and should be replaced by a mobile frequency levelr or 500 khz crystal in the line scanning circuit。
(8) fuzzy。
(a) the black and white noise points on the raster are large or blurred, and the cascading is automatically normalized after 30 centimetres and, if normality can be automatically restored, the catheter is replaced; if no change is referred to as amplification, the focus bits on the mode output transformer。
The "intangible" detection unit circuits and metaware colour television sets have fewer than several hundred and more than 2,000 components, which are impossible to observe on a case-by-case basis. During maintenance, a purposeful focus is to observe certain elements of a unit circuit in conjunction with the failure phenomenon。
(1) the main element of the “nil” unit circuit for the detection of “nil” type failure shall be the unit circuit for the detection of the “nil” type failure. The main observations in the switch power are the safety tube and the large filter capacity and the power thick membrane circuit. The main observation of the line-scan circuits is the line output transformer, which is also observed for the remote colour television. The main objectives of the above-mentioned component observations and the problems described are as follows:
(1) whether the inner wall of the tube is severely blackened or whether the internal fuse is broken。
A. If there is a situation, it is indicated that there is a short-circuit failure of the switch's power, mainly the switch, the power thick membrane circuit, 100 m f/400 v or more, the main filter cap, the bridge plume, and the elimination of internal fragmentation of the magnetic electrical resistance. These elements are the largest vulnerable elements in the switch's power source other than the switch tube, and it is easier to observe that the other elements in the switch's power source and the components in the load do not directly cause the fuse to melt, and the structures and objects in the rationale of the above-mentioned elements, as shown in figure 3。
B. If the tube is not blackened and the internal fuse is normal, indicating that the switch did not penetrate and short-circuit failure。
(2) whether the top of the main filter cap is burst, the top drum rises, and lead to rusty feet。
If there is one such situation, as shown in figure 4. Both indicate that this large filter capacity is defective and should be replaced。
(5) whether the remote transformer looks charred. If yes, the remote transformer should be replaced. Remote transformers are observed only when colour televisions are maintained。
(2) "three nil" with a "creaking" sound, where the main element test of the cell circuit is primarily observed by the row output transformer in the filter large electrolytic convulsor and line scanning output stages of the switch power source. The main objectives of the observation in the switch's power supply, 4. 7 - 100 m f electrolytic, are whether the top is burst or not, and if there is a state of corrosion, it can be judged to be problematic and should be replaced. The observation targets for the line output transformer are the same as those described and in the "nil" above。
(3) the main element of the failure unit circuit in the image (1) the poor impact of the image and the inability of the search station to lock down the unit circuits and components to be observed in the programme。
Two adjacent mid-weeks of public corridors in the main observation shield, such as 38. O mhz image detection mid-week and aft medium-week presence, end of observation if there is no electricity in the dotted frame. If there is a capacitor inside the dotted line frame, remove for two or more weeks to see if the internal cape is partially or entirely blackened and dark, as shown in figure 6. If blackening or darkening indicates a mid-week problem, it should be replaced; if it's clean and fresh, it means it's normal。
(2) the image blurs the unit circuit and the main component to be observed。
Image blurry should be observed to see if the focal point of the cavity tube on the board is rusty and contaminated and whether there is a copper green powder, as shown in figure 7. If yes, indicate a leak in the tube seat, which should be replaced。
Note: the observation focus is extremely important to open or remove a small cap on the back of the tube seat by removing the charge in the inner pressure cap at the same time。
(3) there are cross-disturbed or "s" distortions on the image。
The unit circuits and main components to be observed are 100 μf/400 v or more large filter caps in the switch, and the objectives and results of the observation are described as "none" above。
(4) the unit circuit to be observed for the detection of acoustic failure by the main element of the unit circuit with respect to the acoustic failure is the acoustic channel。
(1) observe the existence of cracks and bursting phenomena in the appearance of the auxiliary device integrated circuit, and, if so, determine whether the auxiliary function is integrated into the circuit through which it is struck。
(2) observe if there is an electrical cap and if the cape is blackened during the middle week of the individual acoustic prognosis in the shield。
(5) the television sets have a fire or smoke failure unit circuit main element detection (1) and a fire sound observation unit circuit and main element。
In the case of a very loud “blow” fire, the main observation is whether the line-out transformer on the line-scanning unit circuit is on fire and, if so, indicating that the line-out transformer is punctured or the insulation performance is reduced。
In the event of a “crystal” fire, the main observation is the presence of purple light in the high-pressure cap of the cathode. If yes, it indicates a decrease in the high-pressure cap insulation performance of the line output transformer, using cotton balls to clean the high-pressure cap of the cathode and replace the high-pressure cap. When the high-pressure cap is replaced, the first is to have good tin on the welding point of the high-pressure line; the second is to have a small amount of silicone (orphant) applied to the two to three cm below the welding point, so that the high-pressure line can successfully penetrate the high-pressure cap. Silicon glue is also applied in the vicinity of the high-pressure mouth of the cathode, as shown in figure 8. Re-emergence of fire failure and tide protection can be prevented。
(2) methods of smoke failure observation。
The smoke-producing elements should be observed as soon as possible and shut down at the shortest time possible. A smoke-producing component is sufficient if it is an electric capacitor, a line output transformer, to replace the smoke-producing element directly, and if it is an electrical resistance, indicating that the electrical current that has been used by the electrical resistance is excessive, it means that there is a short circuit or a passing failure of the electrical circuit at the end of the resistance. Tobacco-producing electrical resistance is sometimes burned off or the value of the barrier is increased; in some cases, it is only visible in a focal form, but the barrier remains normal and may continue to be used after other malfunctions have been eliminated。
(iii) “replacement”
The “empirical approach” and the “intangible approach” described above, in repairing some of the characteristic failures, describe the first-to-be-replacement method as actually being “substitute”。
The “replacement” of the luminium is the replacement of the suspected component by a new component after the failure of a certain component has been preliminarily determined by another method, indicating that the replacement component is problematic if the failure is eliminated: if the failure does not change, it means that the elements that have been replaced are normal, they should be replaced by the television in their original position。
(iv) “touching”
“touching” is the process of turning off the power after 5 min or more hours (preferably removing the power plugs), followed by purposeful touching of the presence of excessive temperature of certain elements。
The main elements examined for “touching” are: magnetic resistance, switches, thick membranes, electrolytic capacitors in power switches; line output transformers and line output tubes in line-scanning circuits; field output blocks in field-scanning circuits (or transmission (a) structural displays out of tube); and acoustic loads in acoustic circuits. The above-mentioned elements, other than electrolytic capacitors, if they have excessive temperatures (except for magnetic resistance), indicate that there may have been current failure of the warming elements. Because the temperature of the components under normal conditions is different, even for the same element, the temperature of the line output transformer varies from machine to machine. As maintenance staff, care is taken to accumulate experience in day-to-day repairs。
It is also necessary to make a special reminder that, in the case of touch maintenance of a component of a unit circuit, a preliminary determination of which component of which unit is the fault must be made on the basis of the above-mentioned “voltage method” or “electric current method” and “experimentary method” in order for the component to be inspected with a “touch method”. Do not aimlessly touch the elements of the switch, so that sometimes the temperature of the different components or the different cores varies, which leads you to misjudge the faults and leads the maintenance into a curve. Be careful not to touch。
“touching” applications in circuits are described below。
The “touching” detection of magnetic resistance is normally carried out at a higher temperature, and the hand should feel hot. If the touch results are hot, it means that the anti-magnetic circuits in the television are working normally; if there is no temperature, it means that the anti-magnetic resistance is not working, it should be replaced。
"tanger" to detect components in a switch power source
(1) the application of the touch switch temperature in the “toucher” in the switch tube may determine whether the working current of the switch tube is excessive. Under normal conditions, the switch is at a certain temperature, and if the touch temperature is the same or below the normal temperature, the working current of the switch is judged to be normal or less than normal; if the temperature is much higher than normal, this indicates that the switch tube is working with large electrical currents, i. E., the load of the switch's power source (line scanning, etc.) has had a flow failure, and frequent damage to the switch is often caused by the passing heat。
Note: if the failure of maintenance is the repeated burning of the switch, the cause must be identified and the failure element removed before the new switch is replaced。
(2) the temperature of the tasting electrolytic cap for the application of the tasting method in the electrolytic cap is such as to determine whether it is leaking or failing. Theoretically, the electrolytic capacitor should be non-temperature, but in practice there are lower temperatures, which should be replaced if the capacitation temperature is high, suggesting that the capacitor leaks; if there is no temperature, the capacitor may fail, it should also be removed for examination。
"touch" detection line scanning circuits have the same elements as other circuit components described above, with a temperature in the line scanning circuits and the line output tube in the normal condition of the line output transformer, if no temperature is felt, indicating that the line output level is not working, but does not result in low output voltage of the switch source (it has a power switch, e. G., the release of the m11 switch); if the temperature is clearly too high, this indicates a leak in certain components of the line-scanning circuit, resulting in a high current at the output level, which is the reason for the low output voltage or the small extent of the raster from the switch。
"touch" detection of integrated circuit integrated circuit "touch" applications is different from the above-mentioned other component "touch". After the integrated circuit is punctured, the engine is turned on for a while after the replacement of the new component, and the temperature is touched when it is shut down. If the temperature is normal, indicate that the field output block or the accompanying sound block has a normal working current and other reasons should be examined; if the temperature is high, indicate that there has been a flow failure, the output level circuit should be checked。
The “touching” detection of other components videos and large-scale integrated circuits, such as cpu, has a low temperature at which to function, and it is likely that the integrated circuit is not working if the temperature is not present。
Other parts have a larger capacity of electrolytic capacitor (above 100 μf) and the temperature is as low as possible in normal times; if the temperature is higher, it needs to be checked if the capacitor fails。
There are more methods of maintaining colour televisions, such as voltage (also known as critical point testing), current, resistance, visual, substitution, disconnection, short circuit, false load, empirical, pressure relief, induction, wave-forming, vibrating (shocking) etc. It is hoped that the most common methods of maintaining colour televisions, as described above, will be helpful。
