LG 42LV355N moving horizontal white/grey lines

[madfreak]

Hi, i got a problem with my LG 42" tv.

It starts to show horizontal lines (grey/white), moving from bottom to top. I 've opened the tv and i do not see any damage ( bulged caps), or any sign of burnt etc.

Does anyone meet with such a problem, and if yes then what should i do to terminate what causes that problem. I also changed (even if they look good) capacitors, but changes nothing . Reseating flex cables also did not change the problem.

I will be gratefull if someone got a little tip, what may cause such a problem

[gilly1984]

Re: LG 42LV355N moving horizontal white/grey lines

Have you tried resetting it?

LG/Zenith:
Hold MENU on TV and MENU on remote for 5~10 seconds, then select reset option.

(Thanks to Tom66 for instructions)

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

Is this an LED TV?
I know some TVs synchronise the backlight and LCD screen to eliminate this very effect. Try reseating cables, as they carry the synchronisation signals. Otherwise, ripple from failed capacitors (elsewhere) could be causing this issue.

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Hi, thank You for Your answers.

I reseated all the cables, nothing...

Resetting tv also change nothing.

Maybe that is important, but after i plug in power cord the screen shows 2 horizontal (white lines ) that have 0.5 cm, and they are moving fast from bottom to top for 1-2 seconds, after those 1-2 seconds those line grow to 20cm, and they then move slow.

That is such a strange problem, i will buy tomorrow 270uf/35v 4 capacitors, and 4,7uf/450v 2 capacitors, maybe that will do the trick but i doubt, because they look fine, without any bulged tops.

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

Definitely sounds like running interference lines -- ever filmed a CRT TV?
The lines look like this in the first seconds: (May appear slower/faster on some other TVs.)
https://www.youtube.com/watch?v=1Vq9_EFaPHk

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Hello again, yes that is almost exaclty the same as on this youtube video just a slower version, but even the size is almost the same ( but mine got 2 of those lines).

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

Two of those lines indicates double frequency or half frequency. I can't think which one right now, but double 50 Hz frame rate is 100 Hz, which is the ripple across the main capacitors after a bridge rectifier. A fault here could cause that ripple effect.

Do you think you can find a way to connect it to a computer outputting a 60 Hz video signal, and see if it changes the line speed? If it does, it is probably those 47uF 450V capacitors. Poland uses 50 Hz, like the rest of Europe, so if it is line frequency interference, the lines should either disappear or move much faster.

If you can, check the voltage across them. In standby, it should be 325V or so; when running, it should be between 385V and 400V.

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

When i connect TV to pc using HMDI cable, the thinkness of those lines change from 20 cm to 10 cm, and they move really really really slow, but they are moving.

The capacitors :

4,7uf/450V :

TV turned ON : 388V
TV turned OFF : 304V

47uf/450V :

TV turned ON : 389V
TV turned OFF : drops from 389 slowly ( probably to 0 if i wait more ).

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

OK, the voltage seems OK, but the capacitors could still have great ripple across them and that might not be picked up by your meter.

One other thing to check would be that the TV and your house have a good ground. The symptoms are similar to ground loops, though I would not expect that over HDMI.

Is there any way to ensure your computer outputs 60 Hz? On Windows, you can use the advanced display dialogue. On Linux, xrandr can help. Dunno about Macs.

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Yes it is 60Hz, its a notebook. I am wonder why these lines change thickness, just like something was warming up, or i don't now

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

You can try to heat parts of the PSU with a hairdryer or heat gun to see if the lines go away or get worse.

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Hello again . I got a progress . I did not get capacitors because of ...... salesman who direct me to point where i can not receive them long story, not worth it to explain more .

But what i had notice When i lift the tv after i plug in power cord, the screen shows only horizontal line but now that line was coloured was thin and she was in the middle of the screen, after 1 second that line dissapear and monitor shows crystal screen with no lines, amudges/ghost etc. like the new one.

So i guess there is some kind of short maybe, or the lcd has some king of damaged connector/tape/pad that is causing such a problem.

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Which part of monitor or which board inside that monitor is responsible for that kind of damage ? Maybe i will look carefully to that part .

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

I am thinking it could be either those 47uF capacitors or a ground loop -- try tightening all of the screws around the main board, t-con and power supply...

[Mr. C]

Re: LG 42LV355N moving horizontal white/grey lines

Hello. I've got the exact same TV as you. Bought it back in April.

Mine has got the same problem as yours.. But I can see, a menu-screen from my DVD-player (Sony Surround sound set) slightly in the screen, EVEN if the screen is on ex. HDMI for another channel, or just another input. And the HDMI for the Sony DVD is not inserted, but I can still see the still-picture. Last I used the screen was a few days ago to watch a DVD, and nothing was wrong there.

What to do?? :-/

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Hello again. After getting all capacitors and replacing them, tv have the same problem. I also order new TCON board, and saddly nothing also changed . I took apart whole lcd panel to see if there is some kind of damaged cable etc. and nothing.

Tv shows exactly the same moving lines.

And also what i had nitice, that few people got exactly the same problem with exactly that tv model, so i guess it'a a "common" issue with that tv-s.

Maybe someone did repair it succesfully, and got a new tip for me ?

Regards

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

So you replaced those large 450V capacitors?

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Yes, to new ones ( all the capacitors are new now ). And the problem exists, it took me long to get new tcon, but it also change nothing.

[tom66]

Re: LG 42LV355N moving horizontal white/grey lines

I'm pretty sure it's some kind of interference getting through. Do you have an oscilloscope, or can you borrow one from a friend? It is probably the LED backlight flickering near the mains frequency.

[madfreak]

Re: LG 42LV355N moving horizontal white/grey lines

Unfortunately no, and i do not know a person who have an osciloscope, so i guess my repair attemp bring me to the dead end .

But... when i took lcd panel apart, i saw that the tv have left and right led backlights, so maybe i will took him apart again, and i will disconnect each other to see if they are the problem.

Can i do it without damaging something ? Or the backlights (left and right) have to be connected together ?