There are three main reasons that can cause screen. One, the screen line off. The monitor always screen when this happens. Second, the screen circuit board insurance fuse. The reaction on the screen is always screen. Third, the screen power conversion circuit fault is the DC-AC circuit, the failure sometimes has a short display or no display then screen.
White screen phenomenon indicates that the backlight can work, first of all, to determine whether the motherboard can work correctly, according to the power switch to see if there is no response, if the light can be changed color, indicating that the motherboard is working properly
(1) Check the motherboard signal output to the screen connector is bad contact (can replace the connector or screen)
(2) Check the voltage of each working point of the motherboard is normal, especially the power supply voltage of the screen
(3) Check the line field signal and the clock signal with the oscilloscope (from input to output)
If the LEDs are unresponsive or not lit, the motherboard is not working properly
(1) Check the work point of the motherboard voltage, to pay attention to the voltage (4.8V), reset voltage (high or low level, according to different models), MCU voltage. If a power supply short circuit, to carefully find short circuit position, there will be PCB board copper foil may be short circuit
(2) Find out whether the contact between the MCU and the motherboard is good
(3) Check whether the motherboard chip and MCU work, can be used to measure whether the crystal oscillator vibration
(4) Replace the MCU if necessary or re-burn the MCU
LCD Monitor what to do with lack of color
Because the display relies on decoding circuit to separate color, there is a lack of color problems, the basic fault is determined in this circuit, the replacement circuit can be resolved. However, some hidden problems may also cause a lack of color, this is very difficult to distinguish and repair.
(1) Check the main chip to the connecting seat between the short circuit, virtual welding (attention chip pin, chip resistance and connection seat, especially flat socket)
(2) Check the screen to the motherboard connector line such as flat cable between the contact is not bad
(3) Replace the motherboard, cable, or even screen if necessary to find out the problem