Display failure, find the fault point and solution

The display is black and has no backlight. The power light is solid green. The squint LCD screen has a display image, which is mostly a problem with the power supply circuit of the high-voltage board.

Focus on checking whether the 12V power supply (fuse F) and the 3V or 5V switching voltage are normal. If there is no output switch control voltage due to MCU problems, the 3-terminal regulator block (AIC1084) can be directly extracted instead. The idea of repairing the high-voltage board (power fuse--- switch control tube--- power management IC - push-pull hair manifold--- power switch tube--- DA conversion circuit (energy storage inductor, rectifier tube) - LC boost circuit (step-up transformer, step-up capacitor) - coupling capacitor --- lamp.

The problem of bright lines, bright bands or dark lines on the screen is generally the fault of the LCD screen. The bright line fault is generally due to a problem with the cable connecting the LCD screen body, or the driver IC of a certain row and column is damaged. The dark line is generally the leakage of the screen body, or the open circuit of the TAB flexible board connection.

The above two problems are basically a death sentence for the machine, and there is no maintenance value, because the ** of a screen is too high.

The problem of a flower screen or a white screen is generally a problem with the driving voltage of the screen, first change the driver board and drive the screen line test, if it is not possible to check the power supply circuit of the screen back plate, maintenance ideas: Whether the voltage regulator block (AIC1084) of the 5V rotation of the driver board has a power supply output. --Screen body driver board fuse (f) conversion circuit --- negative voltage to form IC (-7V) -- row, row drive IC

Color shift faults can generally be adjusted by entering the factory adjustment mode. If there is no such mode, the maintenance idea: replace the screen cable and adapter board--- rewrite the driver -- the driver board is bad (uncommon) -- the control IC of the screen backplane is bad (uncommon) -- unplug the screen cable and observe the backlight color (the flat color of the backlight is the aging of the lamp) -- change the lamp.

Character void or tail maintenance ideas: check the VGA signal line, focus on whether the ground wire of the three-color wire is connected normally--- replace the screen cable or adapter board--- rewrite the driver--- replace the driver board--- LCD screen backplane, signal interface IC is bad---LCD screen backplane, contrast potentiometer adjustment---LCD screen light guide plate misalignment--- polarizer misalignment.

LG with fish screen display,From the current point of view, there are generally two display problems,One is caused by the aging of the lamp,The other is that the display driver board is damaged,At present, it is not easy to judge whether it is a lamp or a driver board,Half an hour later, there should be a desktop display should be the aging problem of the lamp,Generally, it is not expensive to replace the lamp or the driver board,100 up and down is OK,