TCL LCD TV L24E09 sound gray screen repair example - appliance repair - Huaqiang electronic network

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TV model: TCL LCD TV L24E09
Symptom: The screen turns on but shows a gray image, while the sound and other functions work normally.
Diagnosis and Repair: This is a 24-inch LCD TV with a gray screen issue. After checking, the power supply and backlight are functioning correctly, so the problem likely lies in the display panel or the logic board. Upon disassembling, the LVDS output from the motherboard was tested, and the 5V power supply to the screen as well as the signal voltage were found to be normal. This suggests that the motherboard is working properly, and the fault is likely in the screen assembly (which includes the logic board).
After removing the dust cover, the logic board model was identified as M236H1-L01-X+G. A power-on test showed that PANEL VCC was 5.28V, and VAA was 13V. Testing the input pin of U1 (A1AOC25 LDO) showed 5.28V, but the output was only 0.56V. After turning off the power, the ground resistance at the output was normal, indicating that the LVDS signal receiver and timing control chip CM2713A were functioning correctly. Therefore, it was concluded that U1 (A1AOC25) was faulty.
Further testing revealed that U1 outputs 3.3V, confirmed by checking the V33V line. A replacement for U1 was sourced, and a 1117-33 was used as a direct substitute. The repair was completed, and the TV was tested again. The screen now works perfectly with no issues.