After the LCD screen is turned on, the displayed picture is all white, which is what we call the "white screen" phenomenon. How to solve it? We first check the screen cable. If the screen cable is in poor contact, just unplug it and plug it in again, or replace the screen cable with a new one. But in actual scenarios, it is more that the circuit board fails. This requires us to have a certain understanding of the internal structure of the LCD screen, otherwise the maintenance work will be impossible.
01
Die interne Struktur des LCD-Bildschirms
The common liquid crystal displays on the market are mostly composed of driver boards, power boards, high-voltage boards (many are designed together with the power boards), key panels, liquid crystal panels (including liquid crystal molecules, liquid crystal driver chips, color filters, polarizers and Light guide plate, backlight tube, etc.). The phenomenon of "white screen" is mainly related to the failure of the driver board and power board.
1. Leistungsplatine
The function of the power board is to convert the 220V alternating current into direct current, and supply the driving board, high voltage board, liquid crystal panel and other work. If the power supply board is abnormally supplying power to other circuit boards, it will cause a "white screen" phenomenon.
2. Hochspannungsplatine
The high-voltage board mainly converts the DC power output by the power board into the high-frequency voltage AC power required for the startup and operation of the backlight tube. The normal working voltage of the high-voltage board is 12V, and the backlight tube needs a high-frequency voltage of 1500-1800V. But "white screen" means that the backlight tube is no problem, that is, the high-voltage board is not faulty.
3. Treiberplatine
The driving board mainly receives and processes the image signal sent from the outside, and sends the driving signal through the screen line to control the operation of the liquid crystal panel. Therefore, the failure of the driver board will also cause a "white screen".
02
Inspektionssequenz
Überprüfen Sie zuerst die Leistungsplatine: Verwenden Sie ein Multimeter, um die Versorgungsspannung der Bildschirmkabelschnittstelle zu messen. Wenn die Erkennung zeigt, dass der Stromversorgungskreis anormal ist, besteht die Lösung darin, zu prüfen, ob der Sicherungswiderstand oder die Sicherungsinduktivität in der Nähe des Ausgangsendes des Abschirmkabels offen oder beschädigt ist. Wenn beschädigt, ersetzen Sie die beschädigten Komponenten;
Wenn der Test zeigt, dass der Stromversorgungskreis normal ist, ist es sehr wahrscheinlich, dass die Treiberplatine defekt ist. Dann ist es notwendig zu prüfen, ob die Taktsignale und Treibersignale in der Treiberschaltung des LCD-Panels normal sind. Wenn es nicht normal ist, überprüfen Sie das Ausgangssignal, das Eingangssignal und die Versorgungsspannung des Chips, der dieses Signal erzeugt, um festzustellen, ob der Treiberchip beschädigt ist. Wenn es beschädigt ist, ersetzen Sie es einfach.
