According to the sound analysis of the initial sound, the problem may be in the decoding of the video coding and output circuit. Open the installed decoder board box, touch the video coding IC BT852, electricity for 5 seconds that is hot, the temperature rise obviously abnormal. Replace the bt852 after power test machine, repeatedly press the power key and decoding board blue screen output from time to time, a blue screen output can be normal for a long time playback; no blue screen output when the TV screen such as Figure 3 shows dense black and white stripes, similar synchronization. Once again on the boot and green screen or powder screen, in addition to power switch button, the panel other buttons and remote control are not, but the BT852 temperature rise has been normal. Suspected other parts of the decoding board problems. First measure the power supply voltage of the decoder board, even as high as 7.8V, while the normal operating voltage should be 5V. Check for decoding board power supply power supply using the discrete components of the switching power supply, controlled by the main CPU, more complex circuits, and scrutinized the found board power zener diode VD302 weld and post welding everything is normal.xU9service manual download site