LG 42LN5400 - restarts every 10 sec

[YellowJacket]

Hello everyone,

I would like to ask for a little help with this TV. It belongs to friend of mines and he said, the TV is restarting. He uses TV only with HDMI as input.
When I power it up without any video source, it actually works fine - I can see LG logo turning around with "no signal" label, I can browse settings, etc. I tried to hooked up HDMI cable from my computer, and it works fine too ( tested only short time, like 5 min ). But when I connect a USB flash drive, it restarts almost directly every 10 seconds. All voltages looks stable, both on power board and main board. When TV restarts, voltages just fall down to 0V. So no fluctuating or something like that.
Any idea, what can be issue here? I thought firstly about eeprom firmware issue ( when I excluded power supply issue ), but I think, there would be no menu, no remote control reactions, etc with corrupted eeprom. I noticed, the main cpu is quite hot, can't hold a finger on it ( no heat sink on it from factory ), but it is probably normal I guess ( no restart during input from HDMI, so ). Or is this issue all about thermal protection? Will be glad for each clue, thanks in advance.

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

Well, looks like I can't figure it, what causes these restarts. Can someone at least confirm, if it is mainboard issue? If so, which of these two board numbers is correct to find a replacement board? ( upper sticker, or the right one? ). Because I found some used one with number EAX 64891403 (rev 1.0) , but next number is EBR75890817.
Thank you.

[diif]

Re: LG 42LN5400 - restarts every 10 sec

What's on the USB ?

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

Some data ( linux installation files ) and some movies in separate folder. Size of usb memory is 64GB. Anyway, friend said, it behaves the same with HDMI after some time.

[vinceroger69]

Re: LG 42LN5400 - restarts every 10 sec

when you tested the power supply did you test them under load i think you can use car light bulbs as a suitable load

[diif]

Re: LG 42LN5400 - restarts every 10 sec

Some data ( linux installation files ) and some movies in separate folder. Size of usb memory is 64GB. Anyway, friend said, it behaves the same with HDMI after some time.

The TV understands jpg and mp3 off a USB stick.
How long does it stay on HDMI for you?

[dalek1967]

Re: LG 42LN5400 - restarts every 10 sec

I have a 32" LG TV that was acting weird. Sometimes it would come on and work fine. Sometimes I had to unplug, wait 10 seconds or so and plug back in while it had a signal and it would come on. Sometimes it would upset my computer and make the video card disable the port. To say it was flaky is putting it mildly. Finally, I took the back off and discovered that the caps were going bad. They were swollen a bit but working enough that sometimes it would work. I got the info off the caps and ordered replacements. When they came in and I replaced them, the TV has worked fine ever since.

My model is different from yours but I bet the power supplies work about the same, yours likely is capable of handling more current tho. While your problem is sort of different, it could have the same root cause. Just take the back off, see if any caps are swollen. Mine wasn't swollen a whole lot but I have pics in a thread where I posted this info a week or so ago. I can feel they are swollen more than I can see it. That could be my age showing tho.

If the power supply drops to 0 volts, I bet it is because it realizes the power is bad, to much ripple or something, and shuts down. Certainly worth checking.

Oh, my LG had very low quality caps. I was very disappointed to see those cheap things in there. According to another websites tier list, they are tier 4. Basically, bottom of the barrel. I replaced with Japanese caps.

Hope that helps.

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

when you tested the power supply did you test them under load i think you can use car light bulbs as a suitable load

I tested power supply only inside TV, so you recommend to disconnect power supply board, bridge PWR_ON pin to 3.3V via some pullup resistor ( to power the board on ) and load each power lane with some external load?

@diif: oh, I thought that TV can play some movies too. Nevertheless, TV shouldn't act like this even with USB full of unsupported files. On HDMI it worked for me more than 15 min, actually didn't test longer. That's why I stick to USB, since here it crashes all time, and immediatelly.

@dalek1967: there are no visually damaged electrolytic capacitors on the power board ( no electrolytic caps on main board, only ceramic smd ones ). And I measured all power lanes with an oscilloscope, during normal working, and during crashing. There was no weird waveform, no voltage drop, just nice stable DC voltage.

// Forgot to say, sometimes TV freezes instead of restart. I started TV with usb plugged in, TV restarted itself after 10 seconds, and then it freezed. All voltages were present, and stable on power board.

[howardc64]

Re: LG 42LN5400 - restarts every 10 sec

Some data ( linux installation files ) and some movies in separate folder. Size of usb memory is 64GB. Anyway, friend said, it behaves the same with HDMI after some time.

Maybe unlikely solution on USB, I'm guessing your 64GB USB is formatted exFAT? Maybe try smaller USB formatted to FAT32? But hard to imagine TV firmware crash if not understanding USB filesystem.

I fixed one of these that would blank out its backlights after awhile a few months back. I forgot to post result which is rare but it happens and unfortunately don't remember what I did to fix it haha. I did reflow the main SOC. Can try that if you have good equipment or willing to bake main board in toaster oven @ ~400F for 7-8min (lift board up on 4 corners with aluminum foil balls so bottom doesn't sit on the tray) Often, toaster oven is best for people without good reflow equipment. Heat gun can fry the SOC/board if not careful, cold floor + heat gun can wrap and crack things etc.

https://www.badcaps.net/forum/showthread.php?t=108008

[nomoresonys]

Re: LG 42LN5400 - restarts every 10 sec

try it with a much smaller usb drive just to see what happens, like 4gb if you have one, can also try hook up your hdmi and let it run if it don't mess up maybe your friend just has a bad hdmi cable, did he try a different cable or hdmi device?

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

Well, I will try firstly usb with fat32 file system. Next will try to reflow and as last option I will buy replacement mainboard. So can someone help me with these board numbers, from my question in post #2 ?

@nomoresonys - he didn't try anything, just bring it to me. But since it happens to me with that USB, I believe, something is wrong with TV. But yeah, I can try, thanks for advice.

[nomoresonys]

Re: LG 42LN5400 - restarts every 10 sec

big white sticker EBT62498507

[nomoresonys]

Re: LG 42LN5400 - restarts every 10 sec

I always do the simple things first, It's surprising how many times it's just some stupid little thing that's easy to overlook.

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

big white sticker EBT62498507

So the replacement I found wouldn't work then, even if it is from same model TV? ( only number, which fits is EAX 64891403. By a photo on internet it is exaclty the same board ).


Meanwhile I was thinking about one possible culprit: here on my desk, TV crashed only with that 64GB usb. I fix graphic cards more often than TVs, and this behaviour looks similar to VRAM failure in gpus. Is it possible, that this is also memory issue? Never met it in TV fixing.

[nomoresonys]

Re: LG 42LN5400 - restarts every 10 sec

not sure but they are selling eeproms on sj and ebay.

[Diah]

Re: LG 42LN5400 - restarts every 10 sec

there are nothing wrong with TV... its the source problem.
however LG Tv had command IN_STOP.. this will repair and make hard reset to the LG .. in case there are fault at TV

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

not sure but they are selling eeproms on sj and ebay.

I reflowed the RAM memory module, still same. I think, no need to reflow cpu at this point. Do you think, that eeprom binary can be damaged? I mean, everything works, it just restarts at some point.

@Diah: according to google, I was able to get inside hotel mode setup, but surprisingly, there is no Factory Reset option. So I will leave it like it is, try to use different source and cables in my friend's house, and if it won't change, ordering new main board is last chance.

[howardc64]

Re: LG 42LN5400 - restarts every 10 sec

I will buy replacement mainboard. So can someone help me with these board numbers, from my question in post #2 ?

I bought a 32LN5300 main board for the 43LN5300-UB I was fixing. Worked. Board looked same but different PN (unfortunately I don't remember the PNs) I read somewhere (can't find post now) all LN main boards between ~32-50" are compatible. Pros would know for sure.

[YellowJacket]

Re: LG 42LN5400 - restarts every 10 sec

Thank you very much for sharing this experience. And thank you all guys for helping me too. I will try to do something, and if I get some result, will update this thread ( if not, then it doesn't work ).

[vinceroger69]

Re: LG 42LN5400 - restarts every 10 sec

post 20 has a link to the in-stop apk with instructions
https://www.badcaps.net/forum/showth...hlight=lg+stop