If you master this, you will seldom ask if the screen is broken. If you don't want to know too much, if you just want to remember vaguely, please look down. Logic board is the most important link with LCD screen. I will introduce V420H1-C12 to you. I also introduced it as I studied.
Rocket boost has three poles, which pole can not be separated properly will lead to failure, LCD screen drive also has three poles, motherboard one pole, logic board one pole, connecting screen IC soft row one pole. Imagine the importance of logic boards. But there are few data on logic board, which brings difficulties to maintenance. Can we make a good judgement when we suspect that the screen or board has problems? I think it is possible. As long as you grasp the key points of the logic board to detect the voltage, the judgement is handy, because many so-called screen problems are reflected in the key. Point voltage is abnormal. The voltage codes on the board are different, but except for the power supply to the chip itself, they all serve the screen. We don't need to remember which voltage is what, but we need to remember the approximate voltage. If it's basically normal, it's possible to screen out the problem. If it's not normal, it's possible to unplug the wiring or double-row. It's not difficult to understand that when the load is short-circuited, it will pull down the voltage. Fuzzy method is that no matter which power supply on board is what, what label, I only measure whether or not, normal or abnormal, it can be roughly judged. First look at the following picture, then cooperate with my memory song, and then cite three times, for a long time, you can judge freely. In case of endless faults in the central control system, the upper screen voltage should go ahead [logic board power supply voltage, this board is 12V, there are common 5V and small screen power supply 3.3V, etc.] 3325 must have [this is chip power supply voltage V12 = 12V V25-A = 2.5V VD33V = 3.3V, and other chips such as 1.8V power supply] [DC-DC conversion, one high voltage and one low voltage] 5 volts. The lowest to negative [refers to VGL=-5.3V, which is indispensable, this high voltage will appear full screen hard band and other faults, is GATE OFF control voltage] 20 slightly higher to the screen [refers to VGHP=20.4, which is the high voltage of the screen, much lower than CRT Kazakhstan. It's GATE ON that controls the voltage, one turn-off and one turn-on. It's hard to imagine that AA DA is very similar [VAA = 13.8V VDA = 13.8V, very similar, I don't understand what role it plays. Note down, it's only a little higher than the power supply] VGHP is slightly different [VGHP is more than 20 volts and VGH = 18.7V above, so it's a little different, which is important. When VGH is used abnormally, it needs black screen or light screen, no hierarchy, or behind the full screen, you will have a chance to slowly realize that 5533 test point [5.5V is VCOM test point, close to 3.4V is VDD test point,] remember that there are many test points with less effort, but the key point is that VGL VGH is sequentially V12-VDD33-V25V-A-VGL-VG. H. Various boards have different values, but the relationship between these voltages will not change. Just remember a high, a low [negative], a 12V or 5V chip on the screen, 3.32.51.8, and so on. Several copies will be half successful. If there is no label, there will be no quantity at all. There must be a problem.

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