LG TV, after turning on, shows a blue screen with no image, no sound, normal operation of the remote control or unit keys, and the screen displays normal characters. However, when performing an automatic search, no channels can be found.
Beijing LG TV After-sales Service Center case on September 23, 2011.
Analysis and Maintenance: First, measure the tuning voltage and band voltage, both of which are normal. The AGC voltage change range is also normal. Check the voltages of each pin of N101 (TDA8361), and it is found that the voltages of pins 4 and 7 have obvious differences from the normal values. However, checking its peripheral components reveals they are in good condition. Replacing N101, the high-frequency head, the surface acoustic wave filter, and the AFT intermediate frequency transformer is ineffective. Trying to change channels with the remote control, observe that black bars and raster contraction occasionally appear on the screen during channel changes, accompanied by a slight buzzing sound, indicating that the horizontal frequency is incorrect. Measure the voltage at pin 40 of TDA8361, which is normal. Checking its peripheral components, it is found that C212 (4700PF) has changed value.
Solution: Replace C212, and the fault is eliminated.