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How to fix LCD TV flickering - Page 3

post #21 of 36
I think your panel may just have died. frown.gif if its blurring etc, that's to do with decoding of the signal - something's packed in. You could try a replacement BU Board (the right hand one with all the connections), but I couldn't guarantee that will fix it. It could be that board producing a bad signal, or the panel not decoding the signal right. And the panel isn't something that can be fixed DIY. I've damaged a couple of LCD screens in the past fiddling with the ribbon connections to the screens - the connections are hair thin and fragile, even touching them can damage them. I found this out trying to repair a laptop LCD panel that had lines down it, and thinking it was a bad connection, tried to reconnect with a little pressure on the ribbon. All that happened is it got worse.

So, you have 3 options -

1. new BU board

2. new panel

3 new TV

Sorry, but that's how it looks from here. frown.gif

L x
post #22 of 36
actually - having a think - it could still be a power issue - if you have a multimeter, you could check the voltages coming off the PSU (in the low tension side of course, avoid the live mains side). On page 86 of the PDF manual at the top right, you will see the connection to the BU board, you can use that to see where the 12V (reg12V) and 15V (unreg15V) and 3.3V supply is. now the unreg 15V may vary by a few volts, but the 12V and 3.3V should be pretty spot on.

The reason i'm thinking this, is the dark parts of the panel - that screams backlight issues to me, and possibly could be something in the backlight circuit pulling things down, a bad PSU, or back to my origin al theory of something bad in the BU board or panel.

It worth checking all the bases before writing it off.

sorry for the ramble, i'm not the most logical of diagnosers - I go down random paths! biggrin.gif
post #23 of 36
Thread Starter 
Unfortunately I don't have a multimeter. I guess this thing is pretty much dead frown.gif
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post #24 of 36
Top of the panel, under the metal shield is the tcon board. Remove the shield, open the connectors locking the ribbon cables, and also unlock the ribbon cables where they plug into the panel. Remove the cables and clean the ends. I use a burnishing brush to scratch them up a bit where I work. Use whatever you have at hand. Reinstall the cables and the shield and retest the TV. If you're still getting the same problem, try slightly twisting the panel (that is, push it forward at the top left and pull it back on the top right) to see if this makes a difference in the defective areas of the picture.

If it does, try cleaning the two cables a little better. If that doesn't help, some panels allow you to access the small circuit board across the very top of the panel under the chassis. In some cases you can remove a couple of screws and actually remove the top strip of the panel chassis. If you can do this, you can run the tv while gently prodding the ribbon cables that actually attach from this little board to the glass of the panel. Use something like a q-tip or other soft tool to gently flex the ribbon cables. If you find one that makes a big difference in the picture then unfortunately it looks like your panel has had it. The contacts between these cables and the glass sometimes go bad on LCD TVs. and there's not really much you can do to repair them.

On the other hand, if twisting the panel makes no difference (or very little) you may suspect the tcon board itself (the one the cables you cleaned plug into). Sometimes you can find these boards if you have the numbers off of them. A google for the panel manufacturer and the number from the tcon board will often turn up replacement boards.

There should be a sticker on the chassis of the panel saying who manufactured it with the panel number. Try googling it along with the number from the tcon board and/or the word tcon.

Remember, only suspect the tcon board if you're convinced the panel glass-connections are OK (doing the twist test). If it seems to clear up a bit when you twist the panel then it's likely not the tcon board.
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post #25 of 36

Hi Mergatroid,

Can you please look at the video in above link? My TV just started flickering like this since yesterday. I thought it might be due to cable signals or some interference but it behaves like this when playing Xbox or DVD. I tried to upgared the software but no use. also change resoluion to 1080i but it didn't resolve the problem. What will be the issue with the TV.
It is LG 50pk590-ze. Your help will be really appreciated. many thanks all of you who views this post.
Bilal
post #26 of 36
LCD = Flourescent Backlight

That flickering looks to me like the tell-tale signs of dying flourescent bulbs. The question then, I suppose, is the problem actually the bulbs, the power supplying the bulbs, or the electronics controlling the power supply?


Bilalahmed's attempt to hijack the thread is definitely not the backlight and isn't related to your issue at all. It looks like his image is flashing an exact horizontal flip of the picture every so often. I'd suggest going through the setup and turn off each video feature "enhancement" one at a time until it stops doing that to see which one is causing it.

Likely there is a defunct chip in your TV and the board needs replaced. Otherwise, if the TV is new, just swap it for the same model where you got it.
Edited by Electrocutor - 12/13/12 at 12:56pm
post #27 of 36
Quote:
Originally Posted by bilalahmed View Post

Warning: Spoiler! (Click to show)
Hi Mergatroid,
Can you please look at the video in above link? My TV just started flickering like this since yesterday. I thought it might be due to cable signals or some interference but it behaves like this when playing Xbox or DVD. I tried to upgared the software but no use. also change resoluion to 1080i but it didn't resolve the problem. What will be the issue with the TV.
It is LG 50pk590-ze. Your help will be really appreciated. many thanks all of you who views this post.
Bilal

Wow, it looks like you're getting an image ghost flickering in and out for some strange reason. It almost reminds me of a vcr with bad tracking.

That is pretty bizarre. Congrats on coming up with something I haven't seen in an LCD TV before. It's not going to be a backlight as that would note give you the odd ghosted image (although it could account for the odd horizontal noise lines).

There is a board on the back of the LCD panel called a T-Con board. It is usually a small board at the top of the panel with a cable running to the main board, and small ribbon cable(s) plugging into the LED itself.

Both the main board and the t-con board can cause unusual image distortion faults like this.

Personally, I would first check the power board for any bad capacitors. If you have one or more vented capacitors on the 5V line, it can make the main board do some pretty funky things. The 5V is usually stepped down using a regulator to 3.3 or 2.2 volts to run some of the ICs, so any fault on the 5V line on the power board can feed through to the ICs on the main board. Also try unplugging any ribbon cables on the t-con board and give their tips a good cleaning. I might use a burnishing brush to scuff them up good (you could use a very fine emery paper). Just a couple of passes should be good.

If none of those help, and you've tried software and a factory reset already, you might want to consider looking for a main board on the 'net if you think the TV is worth it. I hear Walmart was selling a 42" LCD TV for $299 shipped today (it was on cnet) "deal of the day". Apparently it gets good reviews from owners. You might want to consider replacing it instead of repairing it depending on how much the board costs. Don't forget, this could also be a panel fault, there's no way to diagnose it 100% accurately without subbing some of the parts.
Edited by Mergatroid - 12/14/12 at 7:34pm
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Nukeyork
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post #28 of 36


thanks for your detailed reply. Which one is t-con board in the above picture? I opened the back cover yesterday and tried to check bad capacitor and looose connections. but no joy yet. I also unhooked ribbons from p101 to p204 andthen p201-203 and reseated them.
one thing more, when I press tv menu it appears uside-down like a mirror image of text. plzz help
post #29 of 36
hI,

jUST AN UPDATE. I CHECKED LG WEBSITE FOR TROUBLESHOOTING THIS ISSUE. THEY SUGGESTED THAT IF IMAGE GHOSTING OCCUR THEN REPLACE HDMI CABLE WITH CO-AIXLE CABLE AND IT MIGHT SORT THE ISSUE OUT. AND INFACT IT DID. VERY HAPPY. IT TURNED OUT THAT THERE IS NO FAULT WITH TV, IT IS DUE TO CABLE CONNECTION FROM WALL TILL CONNECTOR.
ALL IN ALL, I AM HAPPY. THANKS EVERY ONE.
post #30 of 36
That's odd. I had thought you tried it on multiple devices, with multiple cables. Are both your xbox and dvd using the same HDMI cable?
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