Smart TV in the home will have such or such minor problems after a period of time, some can be repaired by themselves, without knowing the circumstances after the sale.
1. Judging faults:
To maintain LCD, we must learn to judge which part is faulty. This is the first step. Let's talk about the main faults and location of LCD TV.
1: There is no image and silence when the power is turned on. The power lamp flashes and the screen flashes white when it is turned on. This fault is mostly caused by the damage of the backlight driving board. However, the lamp tube in the screen has also been damaged during the maintenance.
2: Flower screen (mosaic) appears one hour after boot-up, and the sound is normal. The first phenomenon is bad digital board (through hole or IC contact). The second is bad connection in the machine.
3: No startup, power lamp is not on, the first is the power board is broken, the second is the CPU part is not working properly.
4: Lamp flash can not start: CPU bus is not working properly or boot program IC (BIOS) is not good, "BIOS" IC and CPU contact is not good.
2. Maintenance ideas:
1. The whole monitor is powerless.
(1) Power failure: This is a very simple fault. There are two kinds of power supply for LCD extension, internal power supply and external power supply. No matter what kind of power supply, its structure is much simpler than the power supply of CRT display. The vulnerable components are usually small components, such as fuse, rectifier bridge. 300V filter capacitor, power switch, power management IC, rectifier output diode, filter capacitor, etc. IC: 6841 203d06 is commonly used in power supply boards. These commonly used PMW chips can be bought in professional LCD accessories stores like mine.
(2) Driver board failure: the driver board burns insurance or voltage regulator chip failure, some machines are built-in switching power supply, output two sets of power supply, one of which is 5V for signal processing, the other is 12V for backlighting of high-voltage board point, if the switching power supply circuit failure may lead to two groups. The power supply is not output. First check whether the 12V voltage is normal or not, then check whether the 5V voltage is normal. Because the working voltage of the MCU chip of A/D driver board is 5V, when the power fails to turn on, the 5V voltage is measured with a multimeter. If there is no 5V voltage or 5V voltage becomes very low, then one may be that the input stage of the power supply circuit appears. Problem, that is to say, there is a problem in the power part of 12V converting to 5V. This kind of fault is very common. Check the 5-terminal regulator (common model 8050SD-LM2596-AIC15-01, etc.).
One possibility is that the load of 5V is aggravated and the 5V voltage is pulled very low. In other words, the signal processing circuit of the latter stage is out of order. Some of the circuits are damaged and the load is aggravated. The 5V voltage is pulled very low, and the faulty components are checked one by one. When the faulty components are replaced, the 5V can be restored. Normally, the malfunction is usually solved, and it often encounters that the 5V voltage can not start normally after it returns to normal. There are many reasons for this situation. On the one hand, the program of MCU may be washed out, which may lead to shutdown, and on the other hand, the MCU itself is damaged, for example, the I/O port of MCU is damaged, so that the MCU can not scan the keys. When encountering this situation, the MCU can not scan the keys. The problem of finding hardware is useless, even if you change MCU, it can not solve the problem, because MCU needs programming and coding, in the absence of the replacement of the original AD driver board, we can only use the general A/D driver board to replace such as: 151D or 161B.
2. The display will not turn on when it is turned on, but the green light of the power indicator is always on.
This kind of problem is usually caused by abnormal high voltage. It is the action of protection circuit. In this case, it is obvious on the LCD screen. The way to look at it is "squint".
3. Display screen black screen, no backlight. Power lamp green light is always on.
The squint LCD screen has a display image, mostly belongs to the high voltage board power supply circuit problem. The focus is to check whether the 12V power supply (fuse F) and the switching voltage of 3V or 5V are normal. If there is no output switch control voltage due to the MCU problem, the 3-terminal voltage regulator (AIC1084) 3.3V can be directly extracted to replace it. The idea of repairing the high voltage board (power fuse-5V). - Switch Control Tube - Power Management IC - Push-pull Large Tube - Power Switch Tube - DA Conversion Circuit (Energy Storage Inductance, Rectifier Tube) - LC Boost Circuit (Boost Transformer, Boost Capacitance) - - Coupled Capacitance - Lamp Tube.
4. Screen bright lines, bright bands or dark lines
This kind of problem is usually the fault of LCD screen. Bright line fault is usually connected to the LCD screen body wiring problems or a row and column of driving IC damage. Dark line is generally the screen body leakage, or TAB flexible board wiring open circuit. The above two problems are basically sentenced to death, no maintenance value, because the price of a screen is too high.

5. Flower screen or white screen
This kind of problem is usually the driving voltage of the screen is out of order. First change the drive board and drive line test. If the power supply circuit of the back panel of the screen is not checked, the idea of maintenance is whether the stabilizer (AIC1084) of the driving board 5V to 3.3V has power supply output. - - Fuse (F) - 3.3V - - - DC - DC conversion circuit - - - negative voltage forming IC (- 7V) - - line. Column drive IC. AAT1101A M150XN05 power management chip, damaged as a white screen'dim boot image and other AAT1164 M170EG01 new screen common failures, mainly used in the open-base FP71G + LCD. This chip is a high-voltage generation and management chip for LCD. The open-base LCD often breaks down. The breakdown is: white screen.
6. partial color fault
Generally, it can be adjusted by entering the factory adjustment mode. If there is no such mode, the maintenance idea is to change the screen line and adapter board - - - rewrite driver - - - bad driver board (uncommon) - - bad control IC of the back panel - - - unplug the screen line to observe the color of the back light (flat color of the back light is the aging of the lamp tube) - - - - - change the lamp tube.
7. characters are empty or tailed.
Maintenance idea: Check the VGA signal line, and focus on whether the ground wire of R.G.B three-color line is connected properly - - - changing screen line or adapter board - - - Rewriting driver board - - - changing driver board - - - bad signal interface IC of LCD backplane - - - adjusting contrast potentiometer of LCD backplane - - - dislocation of LCD light guide plate - - - dislocation of polarizer
8. There are stains inside the LCD screen
Maintenance ideas: wipe or replace the protective film - - - remove the screen to clean the polarizer and organic glass (with cotton ball, pure water treatment) - - air drying
9. LCD screen leakage or uneven light
Maintenance idea: reinstalling lamp tube - - - adjusting light guide plate
10:LCD screen highlights
One or two big bright spots can be tried to press lightly with fingertips, which can disappear, indicating that the switch tubes and electrodes are mostly connected for this pixel. Small black spots and ash spots may be caused by dust on the inner light guide or polarizer. They can be cleaned and treated.
11:LCD screen has low brightness
Check the ADJ brightness adjustment circuit of the high voltage board, change the lamp tube - - - change the high voltage board - - - adjust or replace the light guide plate
12: Error prompt "Out of Frequency Range"
Check the signal line - - - rewrite the MCU driver - - - replace the EPROM - - - rewrite the EPROM program - - - change the driver board
13: When the power is turned on, the white screen will appear backlight without pressing the switch button. The image after the button can be displayed normally.
The switching signal and ADJ signal of the high voltage board interface are reversed, part of which belongs to the abnormal output of the switching signal of the driving board MCU, which can be repaired by rewriting the MCU program.
14: add a little bit.
When replacing the aging screen of the lamp tube, the size of the lamp tube should be made clear, because although the screen size is the same, the length of the lamp tube is slightly different from the thickness. When the lamp tube of the same size can not be found, it is better to use a short lamp. If not, the slightly longer lamp tube should carefully remove the screen frame with a scalpel and do it well with a heat shrinkable tube. Insulation.

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