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LG 47LW5600, No backlight, no sound, no picture but it turns on...

As the title says, this TV I am trying to fix for a friend of mine. The power on flashes twice red, then turns blue (on). However you get no picture and no sound.

I have thus far checked power in, and it is present at the connector jumping to the main board itself. LED cable voltages ranging between 100-300v when powered on. Not really certain what to do from here. How do I know my main board is good, or sending the correct voltage to the Tcon? I don’t see the same helpful type of chart located on the pcb like the power supply.

Thanks in advance!

Update (09/30/2019)

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Anybody ever fix this. I have the same issue as OP. The power light turns from red to white but I get no picture pr sound

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My understanding is that re-balling the BGA on the main CPU fixes it. May work with a baking cycle in the oven.

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@kg1117 check the fuse on the T-con board and see if you have around ~12V on it. Double check the voltages on your LED connector again. 100V-300V is to much of a variation. Measure all the outputs on the power board to the main board and let us know what you find. Post some good pictures of your board with your question as well as the interconnect wiring. That way we can see what you see. Adding images to an existing question

This switch mode power supply develops Stand By 3.5V at all times when AC is applied. At power on, it develops 12V and 24V for the Main board.

It develops 50V for the LED Backlights.

The fuse F101 and F501 reads approximately 398V (from hot ground) during this time. The transformer T501 delivers an AC signal which is rectified and filtered by D201, D202, C201 and C202 which develops a Stand-By voltage of 3.55V which is used by the SMPS Controller circuit and is also sent to the Main Board It is output P201 pins 9~12 and sent to the P502 on the Main Board.

When the controller chip on the back side of the SMPS receives the PWR-ON command 3.41V via P201 Pin 1, it turns on the Relay RL101 which supplies AC to the bridge rectifier BD101. The primary section (Power Factor Controller circuit) increases its current supplying ability.

Both Primary fuses F101 and F501 now read a little more than 396V. D253 receiving switching pulses from L601 develops the 50V for the LED backlights. When the SMPS receives the DRV_ON command from the Main board via P201 Pin 18 (3.26V) it turns on the on-board Inverter to start driving the LED backlights. The backlight brightness is controlled by the Main board via PWM Pin 22 and Local Dimming signals via P832.

P201 Connector: (To Main Board)

3.5V_ST (3.55V) output P201 pins 9~12

12V (12V) output P201 pins 17, 19 and 21

24V (24V) output P201 pins 2, 3 and 4.

Turn on commands.

P203 Connector: (To Panel LEDs)

50V output P203 pins 1 and 13.

P832 Connector: (To the Main Board)

This connector receives the Local Dimming signals.

P202 Connector: (To Panel LEDs)

50V output P202 pins 1 and 12.

SMPS TEST 1: To Force Power Supply On.

Disconnect P502 on Main board.

(A) Jump pins 9, 10, 11 or 12 (3.5V) to pin 1. Test Voltage Outputs 12V, 24V to Main and 36V to the Inverter Section of the SMPS. Remove AC power. Leave the jumper in place. No Backlights at this time.

SMPS TEST 2:

(B) Jump pins 9, 10, 11 or 12 (3.5V) to pin 18 (DRV-ON). Apply AC power, the Backlights should turn on. Note, the LED B+ will now jump to 65V then back down to 50V.

Note; If there is a problem with a load from the panel backlights, you can remove AC and Disconnect P202 or P203. When AC is reapplied, the Backlight LEDs should turn on for about 4 seconds and then shut off.

So, let us know what you find out

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Well. Fuse on the T-con has 0 volts across it. Also, F101 and F501 both have 330V across it, not 396V. I had to order a mix of jumpers in order to complete the second half of this testing they should be arriving within the next few days.

All voltages are present at the jumper to the main board. The other thing that I went back and checked were my LED voltages, they range from 19-36V with the power on (blue light).

I tried to upload images, not sure if they’re going to post….

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T-con at 0V is odd. Let me check if I have more information on that.

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I have the same TV with the same symptoms. I tried the 2 power supply tests and I have the LED back lights, I can rule out the power supply board at this time. I have zero volts at the Tcon fuse and no back light. I think my problem is with the main board. I have seen some people heat up the BGA engine chip to restore the functions. Would that work in my case? Thanks for the help with the power supply tests.

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Reflowing the XD BGA under the big heatsink fixed it for me.

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I had the same problem, wrote it up in detail at https://lab.remaker.com/2020/11/lg-47lw5...

This is apparently common with the 47LW5600, 65LW6500, 55LW5700, 55LW5600, and 47LW5700, which share the same mainboard (EBT61438207 / EAX63969204).

These systems have a silver BGA chip living under a big heatsink called the XD Engine. Like a lot of BGA parts on consumer equipment (GPU, Xbox, etc), they eventually lose connection to the underlying board. A local shop would pull it off and reball it for $70. Lots of places on eBay also offer that service. So I thought I might try to reflow the chip.

  • Remove the big heatsink. Use needle-nosed pliers on the tabs each of the 4 pins from bottom side of the board: gently squeeze the tabs and pull the pin from the top side of the board. They have springs on them.

Once the heatsink is off, you will see a silver chip with the LG XD logo on it.

  • Lay a piece of aluminum foil on the board, but a hole to expose the chip. If you press the foil on the ship, it will make a convenient outline.
  • Put a line of flux all around the edges of the chip.
  • Clamp the board, level, exposing the top and bottom of the board.
  • Set the heatgun to low.
  • Heat the bottom of the board under the XD chip for one minute, constantly moving in a slow circle in the area.
  • Heat the top of the board for 4 minutes, in circles around the XD chip through the foil hole, making a circle of a 1-2 inch radius, keeping the heat gun in motion. Expect smoke form the flux.
  • After 4 minutes, let the board sit for an hour or so to settle down.
  • Clean up excess flux.
  • Reinstall the heatsink by pushing the pins through the heatsink and board. Add thermal compound if you like. I skipped it.
  • Reinstall the board.

Worked for me.

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