Method 1, the motherboard power supply is normal (5V or 3.3V, some is a single 12V), remote control or button power on or off indicator does not change, generally the motherboard failure. If the motherboard is powered by a single 12V, use Method 1, which is basically not misjudged.
Method 2, first check whether the power supply of each power supply board is short-circuited, and then disconnect the motherboard, add 5v or 3.3V to the power board boot port (PW, PWR, PS-ON, STB), and backlight control on the power board or backlight board. Port (backlight adjustment A/P DIM=PWM=ADJ=OFL=I/EPWM, backlight switch BL-ON=BRI=INV-ON=BK=SW) plus 5v or 3.3V, backlight long light indicates backlight and power supply Normal, you can choose to buy the motherboard. This method is more accurate.
When the backlight is not bright, 24v indicates that the power board is normal, and it also indicates that the backlight or backlight is bad. No 24v means the power board is broken. Note that some screen backlights are controlled by the logic board, and the wired backlight between the logic board and the backlight board needs to be disconnected to start normally.
Some models of TV models are low-level boot mode (such as Skyworth's individual models and Amoi's models), and you cannot use the above-mentioned high-level method. A few brand models (such as Samsung models), as long as the motherboard is disconnected, its power board and backlight board can work normally (the backlight is long).
Gray screen or white screen, remote control or button switch machine is normal, the upper screen power supply is normal, the logic board power supply fuse resistance is normal, the upper screen data line (generally twisted pair) voltage is about 1-2V, most of them are screen bad Individually for motherboard and logic board issues.
Quickly determine the fault method of LCD TV power board, main board or backlight board
One of the faults after the logic board is damaged
Common faults after the logic board is damaged include black screen, white screen, gray screen, negative image, noise point, regular full-screen color strip or ribbon, image is too bright or too dark. Below 26 inches is generally a white screen, 32 inches or more is generally a gray screen, the image is similar to a bad field, the image is still, the image has a residual image (smear), the image is slow, the drawing, the vertical line (strip) or the horizontal line ( Strip), half normal half is not normal, scan line is abnormal (apparently visible), local blackening (variable size) is mostly bad.