LG TV, after turning on, displays no picture, no sound, and no light, while a clicking sound is heard from inside the unit.
Analysis and Maintenance: It's estimated that there's a short circuit fault in the internal power load. After detaching the C terminal of Q402 and measuring its resistance to ground, it reads 0Ω. Reconnecting the C terminal of Q401 and measuring the resistance from the C terminal of Q402 to ground still gives zero, indicating that the line transistor Q402 is damaged. After replacing Q402 and testing the unit, the line circuit operates normally, but the screen remains dark with no light or sound, suggesting there are still faults within the unit. By adjusting the acceleration voltage higher, a faint light is observed in the upper 1/4 portion of the screen while the lower part remains completely black, leading to the conclusion that the issue lies in the field section. Using a multimeter, the voltage at pin 1 of the field output block IC405 measures 0V, whereas pin 2 has a normal voltage of 23V. Further measurements show that the voltages at pins 48 and 47 of IC301 are 0V and 2.3V respectively, suggesting that IC301 is likely damaged.
Handling Method: After replacing IC301, the fault was eliminated.
Technical information provided by the Beijing LG TV Repair Center.