LG 26LG30R Screen issues

[siddiq]

Hi i have this LG 26" lcd tv(26LG30R) and the problem is that when i power it on cold,the screen sometimes freezes and becomes white with black and white horizontal and sometimes vertical lines. i have changed the screen and t-con but problem remains .The funny thing is that it does this for a couple of minutes say, 10mins and when the tv warms up the distortion vanishes and the screen works normally.when the tv is warm i can power it on or off a couple of times without any issues but when i power it on cold,i am back to square one.
All voltages on the power board are accurate,no over heating and there are no bulging capacitors.any help will be appreciated

[tom66]

Re: LG 26LG30R Screen issues

Check the LVDS cable when the fault occurs. It's the cable going from the main board to the T-con. If pressing on it fixes the problem, the connector probably needs a bit of glue.

[siddiq]

Re: LG 26LG30R Screen issues

Check the LVDS cable when the fault occurs. It's the cable going from the main board to the T-con. If pressing on it fixes the problem, the connector probably needs a bit of glue.

Thanks for the reply but what i don't understand is why the tv works perfectly when it warms up and i have checked continuity on that cable and every wire goes through.

[tom66]

Re: LG 26LG30R Screen issues

Thanks for the reply but what i don't understand is why the tv works perfectly when it warms up and i have checked continuity on that cable and every wire goes through.

Because when things warm up, they expand. And expanding things may be good enough such that the TV starts working. It could still be bad caps but I would focus on the LVDS cable first as I had a TV which would start up but the colours were completely wrong. After about 10 minutes the picture would become much better. I found I could make it better immediately by pressing on this cable. The glue on it had dried up and re-doing the glue fixed the problem permanently (I used higher temperature glue this time, so it shouldn't happen again.)

[siddiq]

Re: LG 26LG30R Screen issues

Because when things warm up, they expand. And expanding things may be good enough such that the TV starts working. It could still be bad caps but I would focus on the LVDS cable first as I had a TV which would start up but the colours were completely wrong. After about 10 minutes the picture would become much better. I found I could make it better immediately by pressing on this cable. The glue on it had dried up and re-doing the glue fixed the problem permanently (I used higher temperature glue this time, so it shouldn't happen again.)

Thanks,i will try it and post results.

[siddiq]

Re: LG 26LG30R Screen issues

Hi everyone,especially tom66.I have checked the lvds cable thoroughly and it seems to be okay.I want to post some pictures of the various stages when powering up the tv to see if you can have an idea as to the problem,thanks and a happy new year.

P.S i am having security token issues so i'm posting pics from a url.
http://www.mediafire.com/?la99fx3hl4dvz8t

[tom66]

Re: LG 26LG30R Screen issues

Those match similar symptoms for an LVDS cable problem, but clearly it isn't that. Another possibility is damage to the panel ribbons. Unfortunately this isn't always possible to repair. You can sometimes verify this by applying a *small* amount of pressure to the top and side of the screen, do the symptoms change?

Could also be a T-con problem, wouldn't rule that out entirely.

[siddiq]

Re: LG 26LG30R Screen issues

Those match similar symptoms for an LVDS cable problem, but clearly it isn't that. Another possibility is damage to the panel ribbons. Unfortunately this isn't always possible to repair. You can sometimes verify this by applying a *small* amount of pressure to the top and side of the screen, do the symptoms change?

Could also be a T-con problem, wouldn't rule that out entirely.

The symptoms change when pressure is applied to the top and sides of the tv but after it heats up the tv can be on all day without issues and "twisting" the sides of the tv has no effect.

[tom66]

Re: LG 26LG30R Screen issues

The symptoms change when pressure is applied to the top and sides of the tv but after it heats up the tv can be on all day without issues and "twisting" the sides of the tv has no effect.

You have bad tab bonds then. This is sometimes fixable but not always. You will need to take the metal casing off the TV screen and you should be able to see ribbons connected to the screen. Press individually on these until you locate the faulty one. Some people have had success with putting foam or other objects inside the metal casing, permanently applying pressure, but this doesn't always work.

[siddiq]

Re: LG 26LG30R Screen issues

You have bad tab bonds then. This is sometimes fixable but not always. You will need to take the metal casing off the TV screen and you should be able to see ribbons connected to the screen. Press individually on these until you locate the faulty one. Some people have had success with putting foam or other objects inside the metal casing, permanently applying pressure, but this doesn't always work.

The problem right now is that the old screen I changed was behaving similar to this one. Is it possible that both screens are damaged? I will try the pressure thing and see if it works. Thanks for your help.

[tom66]

Re: LG 26LG30R Screen issues

The problem right now is that the old screen I changed was behaving similar to this one. Is it possible that both screens are damaged? I will try the pressure thing and see if it works. Thanks for your help.

Maybe, but more likely you have a cold joint or a loose connector. How are the ribbons going from T-con to the LCD panel? Are they firmly fitted?

If you have the ability to do so, consider re-flowing the joints around the LVDS cable on both sides, to see if it fixes the problem. You'll need a soldering iron, thin solder and a steady hand. Don't do this if you aren't confident, you could damage something.

Also, post a picture of the power supply (vague chance bad caps are causing this.)

[siddiq]

Re: LG 26LG30R Screen issues

Maybe, but more likely you have a cold joint or a loose connector. How are the ribbons going from T-con to the LCD panel? Are they firmly fitted?

If you have the ability to do so, consider re-flowing the joints around the LVDS cable on both sides, to see if it fixes the problem. You'll need a soldering iron, thin solder and a steady hand. Don't do this if you aren't confident, you could damage something.

Also, post a picture of the power supply (vague chance bad caps are causing this.)

I will consider re-flowing, and i am very capable . I have posted pics of power board and t-con.

[tom66]

Re: LG 26LG30R Screen issues

I can't quite make out the readings on the pins but check that the labelled voltages appear on the correct pins.

[siddiq]

Re: LG 26LG30R Screen issues

I can't quite make out the readings on the pins but check that the labelled voltages appear on the correct pins.

Hi, i am back one last time.It turned out that the problem was the screen (bad tab bonds).The first tab was the culprit,and after applying some masking tape and a little pressure from a piece of foam,the tv is good as new .Thanks for all the help tom66,happy new year and more success ahead.

[tom66]

Re: LG 26LG30R Screen issues

Hi, i am back one last time.It turned out that the problem was the screen (bad tab bonds).The first tab was the culprit,and after applying some masking tape and a little pressure from a piece of foam,the tv is good as new .Thanks for all the help tom66,happy new year and more success ahead.

I am glad your TV is working. I'm also glad you could fix the tab bonds - as repairs on these bonds aren't always successful.

[senndogg]

Re: LG 26LG30R Screen issues

tab bonds! just going to say that