Chosen Solution
LG 55EC930T The TV still can be turned on by the remote or the power button. I can hear the click from the powerboard and the red LED on the mainboard will be on. But no picture no sound. My nintendo switch can turn on the TV via HDMI as it normal dose. Tried disconnecting speaker, control button and remote receiver one by one noting worked. Tried disconnected the T con board. The power can be turned on for 2 second and then it will restart it self. And the power stay on for another 2 second before turning off. Bought a mainboard and put it in, but issues are same. Tested the power suppy board. The power to the mainboard showed in the pictures. The power to the T con board are all 25.1V for the 24V pins and -1.2mV for the GRD pins. Is there anything I can do? Many thanks.
更新 (2020年09月20日)
@lleei since you already replaced the main board the next logical step is the power board. Post a picture of the complete power board. Update (09/20/2020) @lleei sure looks like a beast. I attached the testing procedure for the power board (don’t let the description fool you it’should work for yours as well), see if you can work through that. The voltages you listed are all good. Do not forget to test all the fuse on the board. If that all pans out we should not forget the T-con board. I wonder if it fails to post and hence no sound/video. It’s uncommon to do that but it is an LG so…. OLED SMPS Testing
