TCL LCD TV logic board 37T03-C04 white screen troubleshooting - Home Appliances

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A TCL37-inch LCD color TV, the sound is normal, a white screen appears.
The past experience is roughly located on the logic board. The gamma correction chip model of the local logic board is AS15-HF. The chip has 22 sets of gamma voltage and 14 operational amplifier circuits, all of which follow the emitter follower. In the form of a layout, the non-inverting input of the op amp is connected to a low-to-high step reference voltage. The output produces 14 steps of gamma voltage.
The chip reference voltage output pin: 7, 23, 24, 25, 26, 27, 28, 29, 32, 33, 34, 35, 36, 38;
Gamma voltage output pin: 1, 2, 3, 4, 5, 6, 9, 10, 11, 12, 13, 18, 20;
Power supply - VDD pin: 8, 15, 22, 30, 43, 45;
VCOM pin: 39 input 47 output;
Ground VSS pin: 7, 19, 21, 31, 44, 46;
After detecting the reference point of the logic board, it is found that only the VCOM point has no voltage, and the other reference point voltages are basically normal. Suspected that there is a problem with AS15-HF, immediately replace the chip AS15-G, I thought that the medicine should be removed from the disease, otherwise the fault of the power-on test is still the same, where is the problem, meditation... Inference chip VCOM voltage There are 47 feet of output, lifting the test leads 47 to the VCOM reference point, the resistance is infinite, the board line has a section, this can not be sloppy, test VCOM reference point to the two screen line 15 foot line is normal, tested straight through, the rest Chip 47 feet - VCOM reference point line open circuit problem, too lazy to find. A flying line is shown in the picture, and the clear image is displayed.