My LG TV 55lv5500 suddenly turn black with no sound or picture.

"jpwinarto this sounds more like a power board issues. You do want to start by checking the power board voltages. Post some images of your boards with your question by using this guide. There are two different power boards depending on the type of LED backlight.

and

check the connector (red rectangle) to see if you get those voltages:

1 Power on

2 20V (24V)

3 20V (24V)

4 20V (24V)

5 GND

6 GND

7 GND

8 GND

9 3.5V

10 3.5V

11 3.5V

12 3.5V

13 GND

14 GND

15 GND

16 GND

17 12V

18 Inverter On/off

19 12V

20 Lamp : A-Dim LED : N.C

21 12V

22 PWM Dim #1

23 NC

24 Error-out."

"Hi.

I had the same trouble on a 42LX6500. TV powers on, but no video, backlight or sound. Nothing.

Checked voltages and power-on signal as explained by oldturkey03 but voltages were correct.

So, I decided to reflow LGE3556C under brown heatsink and it is working now. A professional reballing should solve this definitely."

The heat cause the chip to seat to the board, giving it the contact it needs. When the chip was not properly seated when first placed over time heat will cause them the separate. The key is not to apply to much heat or you will damage the chip. Follow the simple quick fix and you should be enjoying your TV for many more years to come.

What can I do if I have no heat gun? Any success in the oven?