Solve the problem of laptop screen become dark

Have you ever experience that the laptop screen is so dark you can barely see anything. It will be fine if you attach to the desktop monitor, but the laptop screen stays dark? How to sove it?





What’s the meaning of laptop LCD screen brightness is not enough? We call this phenomenon as "dark screen" means that the ignition coil failed to supply electricity to the lamp on the LCD screen.





People who use laptop regularly knows that there is a small lamp for bright to LCD screen, so people mistakenly believe that the lamp burned when the screen become dark. Let’s have a detailed explanation for screen dark failure.





Points caused screen dark failure is four:





1, Fluorescent tubes disconnected (Generally, laptop lamp will not be destroyed by the high-voltage in the normal use, the reason of lamp off is mainly due to laptop fell to the ground and lamp strikes grave.)





2, Ignition coil no power supply to the lamp (The motherboard with 3-4 group of voltage for the ignition coil, ignition coil through the chip for the transformer to the lamp post, chip aging or over-current burn without electricity output.)


3, Motherboard no power supply to the ignition coil (There are 3-4 voltages group in the motherboard to the ignition coil, and two groups-chip output voltage to high voltage board, chip aging or over-current burn without electricity output)





4, Cable disconnect (There is a connecting cable between the motherboard and the ignition coil, for a long time moving LCD screen cable disconnected, resulting in no main electricity supply to the ignition coil.)





These four points are the major reasons caused by the dark screen the first three are more emerged, the fourth point of the opportunities arise is relatively small, because the connection line is to use a special kind of shield is covered with it and a small number appear to connect line disconnected phenomena. Professional maintenance staff for the detection of each process are essential.





The following is a special case in the testing process:





The problem descrition: People rebooted the laptop after laptop standby, and the laptop screen became dark, entered WINDOWS must depend on the shining lights in the outdoors, then suspected to have no electricity to supply of high-voltage lamp. The first thing to do is connecting the external PC monitor to see if it can enter WINDOWS properly. This step is very important to determine whether there are other problems of hardware and software. Generally, professional maintenance center will test hardware and software to ensure the phase-side will not be conflict of interest.





After the failure was determined, we can start to dismantle the screen frame, in general, around the screen are 4-6 screws hidden, so we must remove the screws first, and laid the back frame out. The frame will get a serious crack if the screws stay. You will find that there is a white plastic insulation, the above is written note: CAUTION: HIGH VOLTAGE.





This is a high-voltage plate, we can find the high-voltage structure while demolition of plastic insulation. The motherboard has four cable to connect high-voltage plate and through the chip distributing voltage to the coil, then light the lamp brighter.





First, we use the substitution to test lamp is disconnected, remove the lamp from the high-voltage plate and placed in a pre-prepared tube. If no reflection after boot, rule out the reason of lamp. The we test the motherboard supply the 3-4 group high voltage to the board, connect motherboard to the high voltage board and split out to use multimeter to test voltage.





We can see that the motherboard is now just using 5V voltage for the high-pressure plate, if the motherboard has problems, it may lead some consequences not good, so the steps of process of testing each one are necessary.





There are two holes at the top of the host, it can come up with a hard object, then the connector links motherboard and high voltage board come to our eyes. We continue to use the multimerer to test the connection port location of power supply is normal, strange things happened at this time, the interface of motherboard voltage id normal but the other side of the voltage is gone. Is it the problem of cable. We remove the axis which covered the screen to see the location of line has been turning roll up into a ball, initially suspected to be due to a long swing-screen product line disconnected. We split the cable from the motherboard out of measurements at both ends to see connected or not.





After finding the problem and then we recruited three cables to disconnect part of the extension of welding well, and use shielded wire to wrap in then boot. Fluorescent tubes and displays finally normal, although the process of detection and the process sequence spend a lot of time of engineers. The most suffering is consumer if the unprofessional maintenance center failed to get cable on the test part of the chaotic demolition motherboard testing, and come up with more questions if not the corresponding anti-static equipment.