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Troubleshooting of Changhong LCD TV
Source: http://xrqa.cn Author: Mianyang Changhong air conditioning after sales maintenance update date: 2015-09-09 20:40

Mianyang Changhong TV after sales service center solves the problem step by step
I. black screen (power indicator is on)
This kind of fault should be started from two aspects
1. Check whether the inverter works. If the lamp tube is not on, first check whether the control signal standby is normal, and then check whether the inverter power supply + 12V and 5V are normal. If there is no power supply, the + 12V fuse resistance is open circuit and can be replaced. If the power supply is normal and the lamp is still not on, the inverter board needs to be replaced.
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2. If the lamp is on, it is necessary to check whether vccpanel (3.3V) of LCD is normal. If not, check the control signal of LCD power supply (blon should be high level). If not, check whether the CPU works normally. Generally, replace the CPU. If the control signal is normal and there is no 3.3V power supply, si9430dy (U15) needs to be replaced.
2. White screen (the whole screen presents a very bright white grating)
1. First of all, check whether the connecting wires (pj1 and pj2) between the LCD and the signal board are in poor contact. If it is really a poor contact, plug the connector again.
2、 Another common case is that the PvdD (3.3V) of a / D converter decreases even to 0V, ad9884 (U4) does not work, there is no digital RGB signal output, and the LCD signal electrode has no working voltage, which is equivalent to that the LCD box is not powered on. According to the principle of the display, the LCD screen is in the light transmission state, so the whole screen presents a very bright white grating. After inspection, it is found that L11 inductance fails early, and the resistance value increases, resulting in the decrease of PvdD power supply.
3. Screen color deviation
If there is a slight color deviation on the screen, First, enter the factory mode (turn off the display by turning the power switch, then press and hold the "" key and the "select" key at the same time, and then turn on the power switch). At this time, the screen will enter the state of swiping, and it is found that there are asymmetric interference fringes on the screen. At this time, it is necessary to check 24C16 (u9). Even if the measured working voltage is normal, it must be replaced, and generally it can be repaired.
4. The screen lacks color
In this case, the A / D converter usually has no analog R or g or B signal input. After inspection, it is found that L3, L4 or L5 fail early, resistance increases or open circuit, resulting in no primary color signal input.
5. Red screen
If the red screen appears on the whole screen, it is necessary to check the frame memory U2 and U3. Even if the memory power supply is normal, it is necessary to replace U2.
6. "Signal out of range" appears on the screen
In this case, it is necessary to eliminate the two cases that the signal received by the display is not standard or beyond the display format supported by the display. If it is the fault of the display, the analog line field synchronous signal must be checked. Generally speaking, R39 and R40 fail early, resulting in the increase of resistance value or open circuit, resulting in no line field synchronous signal input into the A / D converter.

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