Changhong plasma TV 3DTV42738X does not power on after the logic board red light is on three times - android - Phones Developers

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Renovated a Changhong 3D plasma TV, the model is 3DTV42738X, the fault is not open. At the moment of power-on, the red light on the logic board (board number: JUQ7.820.00046731Ver4.0) is turned off three times, and then the relay on the power board rang and no response. When the power is turned on, the power supply board (board number: XR7.820.078 V3.1) has a secondary output voltage of VSUS=210V, V0=57V, and D15V=15V. Both are normal. After the relay is activated, the output voltage of each unit is gone. This power supply drawing can not be found everywhere. This power supply does not work alone (short-circuit the PS-ON switch to the ground). The main power supply has no voltage output regardless of whether the bulb is connected or not. The standby sub-power supply 5V is normal. It is found that there are several solder joints on the power supply board. After the repair welding, the red light flashes on the power logic board (second flash, always flashing), and the power button can be turned on.