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LG TV won't turn on after lightning surge.

After a lightning hit my area my TV turned off and won’t turn on again. There is no standby light.

I unplugged it and plugged it back in but it didn’t work.

I pressed and held the power button for 30 seconds, waited 1 minute and tried to turn it on but it didn’t.

I opened the tv and checked the fuse, but they were okay.

I checked the standby voltages and they were all good.

I even tried baking the main board but it didn’t work either.

What else can I do besides replacing the main board?

NOTE: I think this issue resulted from the HDMI port because the device connected to this port doesn’t turn on either.

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Can you post pictures of the circuit boards inside your TV? Aggiungere immagini ad una domanda

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Helo Gabriel,

Did you solve the problem? Similar stiuation is here

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Hi,

How many fuses did you check and how did you check them? Do not only check them visually but use a multimeter to check continuity, as many times a blown fuse might look ok.

How did you check the standby voltage? Using a multimeter? Where did you measured them and what did you get? On the AC or DC side? Maybe both?

Have you checked ALL areas of your TV’s boards and are you sure that there’re no signs of burnt components?

Have you checked the aerial connector area? It is usually shielded with a metallic box to avoid EMI and EMC issues.

If the lightning surge was close enough to your home aerial, the static might have blown some of the RF electronics withing the EMI cans, and possibly propagate the overvoltage to the rest of the TV damaging more areas of the electronics. Some times I’ve seen the RF receiver boards as independent PCBs. Check that you didn’t miss the inspection for burnt components on any board, and have a look inside the EMI cans if possible.

Good luck!

Edit:

I see you have updated pictures.

The bottom face of the motherboard seems to have quite burnt areas. I don’t know if that’s an effect of the picture, or maybe that the board has not been cleaned after a repair, or maybe because of the lightning surge. Anyways, the area underneath the aerial connector looks bad.

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If the EMI can lid on the top face is not soldered to the walls of the shield, try to open it to see if it hides any damaged component. You also can try smelling around it before trying to open it. If it smells like burnt plastic…you have your damaged area.

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I checked the fuses using a multimeter. I checked 2 fuses that I noticed in the power board. I switch the multimeter to the diode mode. When touching the fuses sides, the multi meter started beeping which I think it means it's okay.

I checked the standby voltages again with the multimeter and received 3.5V 12V and 24V on the pins as it should. I switched the multimeter on the 200V DC mode to check these voltages.

I also checked these same voltages on the main board side and they were all good.

I didn't check anything else on the power supply board because the voltages were correct so I'm assuming it is okay. No component looks burnt to me.

What's the aerial connector area? I don't know what this is. Sorry, English is not my native language.

I don't know what other component to check. Any ideas would be appreciated.

da

Hi Gabriel,

Based on the pictures and the description you gave me, it seems the problem is not in the power board.

No worries, english isn't either my native language :)

The aerial, or antenna, connector area is the are one that I have marked in the edit of my original message. It's basically where you connect the cable of your antenna.

Have a look of what I say in the edit of my previous message and ask if you have any question!

da

Hi again. Thanks for your quick replies. I'm not entirely sure, but those black spots at the back side of the main board appeared after I baked it. 😅. But I'm not 100% sure though. As for the antenna connectors, I didn't check but I can tell you that I've never used those connectors. I receive my signal from a device which is connected to one of the HDMI ports. As I mentioned in the question, that device got burnt too, so I'm assuming this originated from this external device connected to the HDMI port.

With all what I said, where do you think the problem is and what would be the best solution?

da

Ah, ok, makes sense!

Is that external device you had connected on your TV a DVB (Digital Video Broadcasting) or digital television converter? Is that device connected to the aerial/antenna?

If I insist with that question is because after a lightning surge you device can be damaged because of a overvoltage caused by an excess of static coming from the power plug, or from the antenna connector.

That overvoltage failure then might propagate to other devices connected each other, or to the grid.

If in your house only the external device and your TV was damaged, then most likely the problem started within your external device, that propagated to your TV.

The answer of this question would give you and idea of where put your attention to: the power supply board or the motherboard (1/2)

da

(2/2) If we assume that this is the case, you would need to trace for signs of damage around the HDMI connectors, and everything that is connected to them.

The HDMI connects directly to the TV CPU (the big silver square on the center-bottom of the motherboard's top face). In case of overvoltage, the issue might have propagated to the CPU causing potentially a domino effect problem to the rest of the board.

The quest you have ahead is not a simple one. It would cost you hours of debugging with the multimeter or oscilloscope. In the best of the cases.

If I were you, I would try to find the schematics of the TV. Then I'd try to check if all internal voltages after the DC/DC and LDOs are ok. Even with the schematics, this might be difficult if you are not sure what those acronyms stands for...

After you have checked all voltages on the board are the correct ones, I would go part by part to identify parts that are clearly not working well, and then I would try to trace down the root of the problem. (2/2)

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Electronics hit by lightning and flooded cars are in the same category: junk. You can spend a lot of time chasing down bad parts but odds are that you will never get it to work again. The most vulnerable parts are integrated circuits with very small junctions that will fry at a few volts, and lightning is a million volts so your chances aren't good.

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@col_panek Why not replace all the circuit boards then? The panel is the valuable part, and most times it's still working.

da

@col_panek in general I agree with your statement "Electronics hit by lightning and flooded cars are in the same category: junk". The only good thing is, that I can replace the individual boards on a TV but not in a flooded car. Replacing the main board or the power board commonly fixes TV's and keeps them out of the Landfill. Reason for the existence of iFixit. Repair is War on Entropy!

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I think I have the same problem with my 50 in LG plasma. My electronics skill is basic, took the tv to service anyway, and they said “probable lighting surge through the hdmi connect” They said best case scenario is to try to put replace the motherboard or send it off to be repaired MAYBE but it would cost $250. Not worth it in my opinion. I hate to add to electronic waste but unless its a straight forward board swap from eBay, it may be a done deal…

Any advice is appreciated.

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@redb27239 we would need to know the exact model for your TV as well as see the individual boards. you up for it? Wanna try? :-)

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@oldturkey03 Sure! Got to get it back from the TV shop, but I’m down! ;-)

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@redb27239 whenever you are ready, just holler. Let's get it done (one way or another)

Repair is War on Entropy!

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Gabriel Kuka sarà eternamente grato.
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