Example 1: A used NEC15-inch LCD display failed because the power indicator was on, but nothing was displayed on the screen.
Fault analysis: The LCD power indicator lights up, at least indicating that the monitor power is good. However, there is no display on the screen. The most common situation is that there is a fault of poor contact between the LCD control module and the segment electrode of the LCD panel.
Troubleshooting: Disassemble the display case, you can see the control circuit and power circuit two modules of the circuit board. After the circuit board is removed, the X and Y electrodes of the display panel are exposed and the data line is drawn (X electrode is referred to as the back electrode, Y electrode is referred to as the segment electrode), and then detection can begin. We know that the segment electrode of the LCD screen and the output drive pole of the display module are connected by conductive rubber. This is in the same way that the swipe screen of a calculator or electronic watch is connected.
Check screen simple method: using a common wire, will be the one end of the insulation cortical strip for a short period, then the other end in the lamp (other household appliances may also) around in circles on the power cord, so the wire will produce a weak induced voltage, while the induced voltage of the internal resistance is large, and with only 50 Hz ac induction electromotive force, it had little effect for general household appliances, but used to drive LCD display device is just fit. With his left hand holding onto the back of the LCD panel electrode lead wire or contact with a metal probe it can each column pixels back electrode (together), and with her right hand then just have induced voltage that wire, contact each period, each in the thrum of the bare electrode (i.e., Y electrode), as long as the corresponding pixels in different period of electrode reaction, it can be concluded that the screen is good.
When the wires came into contact with each electrode, the LCD responded. It was concluded that the fault occurred on conductive rubber, possibly due to poor contact. The author cleaned the conductive rubber with high purity anhydrous alcohol and put it back to its original place. Then, all parts were restored. The power-on test display could display normally and the fault was eradicated.
Maintenance summary: Why not use the multimeter’s electrical barrier to provide the driving voltage of the segment electrode? Because the multimeter electrical block is provided by 9V ~ 15V DC voltage, the watch pen for a long time in contact with the electrode will damage the LCD panel, and the above-mentioned method is to provide a weak ac current, relatively safe (this is determined by the nature of the LCD panel, the author will not explain in detail). However, it should be noted that during the test with this method, it is possible that the corresponding pixels of the electrode in the segment not in contact with the wire probe on the panel also react, which is caused by the induced voltage on the suspended electrode, which is a normal condition.
LCD display components are relatively fragile, disassembly must be careful, must pay attention to anti-static, at the same time to pay attention to the LCD display is also high voltage. Also, the removal of the LCD monitor is limited to the removal of the circuit board. If you remove the LCD panel, the monitor will be scrapped.
Example 2: A generic 15-inch LCD display with a chaotic and unstable screen.
Fault analysis: refer to the method in the above example and test after processing, the fault is still found. However, when the author inadvertently moved a bass speaker on the computer desk, he found that the display picture on the LCD screen also changed. The author immediately cut off the power supply of the speaker and moved the speaker away from the computer desk. At this time, the display suddenly resumed its normal display, and the fault was cured without a cure.
Maintenance summary: some users mistakenly think that, unlike the CRT display LCD, and fear for shadow mask plate and magnetic deflection system magnetic field interference, actually LCDS often work in the field, will also affect the normal work (open LCD you know, a good LCD control circuit board has a metal layer of outside magnetic shields).
LCD display, although the price is not high, there are various problems. It will have various effects on our work and life. In ordinary life, when using LCD, as long as pay attention to the following points, will extend the life of LCD.