LG5270 LCD TV - Lines and designs

[OldMan]

Picked up a 52" LG LCD which turned on to a very dimly lit screen. I figured it was a power or display drive board issue. I hadn't touched the TV because of a busy schedule in about 2 weeks and today when I was testing it I encountered a very different symptom. It now turns on and has sound if an input is plugged it. The video comes up as rainbow vertical lines and strange grey boxes. I have attached a couple pictures to illustrate what I mean.

I can unplug one of the 4 ribbon cables going to the TCON board and make that quarter of the screen to black. Depending on which portion I unplug, the colors come and go as expected.

I'm wondering if anybody has experience with this or could weigh in on if my TCON has failed (never encountered this in my repairs) or if I have a strange LCD failure (typically fail with just lines and no designs)

Any comments/suggestions are appreciated.

[tom66]

Re: LG5270 LCD TV - Lines and designs

This definitely resembles a video board failure - either the T-con or main board. The split in the screen definitely leans towards a T-con issue. I doubt it's a panel failure, it's too "discrete" - panel failures usually lead to black bars or blurry parts.

If you connect a video+audio source to the TV, can you hear anything from the speakers? You may need to flick through the inputs using the INPUT button.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

tom - yes I can get audio out of the speakers. I've only tried the vga input with my laptop but in my experience once i have audio once, it works on all inputs. i've also had experience where if audio works, the video works once i replace another part on board (tcon,inverter,psb)

[tom66]

Re: LG5270 LCD TV - Lines and designs

Can you check the supply voltages on the PSU? Post a picture of it if you need help. I have seen this symptom with a bad PSU.

Also, do the lines move or change if you turn the TV off and on?

BTW, my LG 42LC46 dims the screen with no input so I think that isn't a problem if the screen is dim with no input.

[infringer]

Re: LG5270 LCD TV - Lines and designs

Tom66 if the lines did move would you say this is more so the video board or TCON board you brought up an interesting comment just figured I would dive further into it.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

Lines do not move from their positions when TV is turned on/off. I checked several times. I did notice that the lines seem to gradually appear from middle to edges over about 3seconds when I power on. Almost like a slowly appear PowerPoint transition (if you're familiar with this look)

Voltages seem quite normal. Standby is 5v. Power to main is 12v when on. 24v to inverters.

I'm thinking about replacing the TCON at this point....

[tom66]

Re: LG5270 LCD TV - Lines and designs

Yeah, 95% sure that's a T-con issue. Main boards don't cause a fading effect usually. Just make sure you order the one for the exact panel in your TV (check if it is an LG.Philips LCD panel.)

[OldMan]

Re: LG5270 LCD TV - Lines and designs

I'll update back with what I find out. Hopefully ordering the new TCON tonight. Stay tuned.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

Here is where I stand:

I've replaced the TCON board with the exact board and it solved my initial issue with the lines. However, now that my lines are gone I don't have any video showing up. The screen still illuminates telling me the inverters are just fine. My sound also works, even when I switch to different inputs. Switching out the video board with another of the same number does not change anything.

So what should I test next? Perhaps my video board is not getting the power needed to output video? I did

[budm]

Re: LG5270 LCD TV - Lines and designs

So the screen just have slight glow to it without any pictures or on screen menu? It sounds like a dead T-CON or it is not getting the power. Cable seating are good?

[tom66]

Re: LG5270 LCD TV - Lines and designs

I suspect you got a dud T-con or the LVDS is not properly seated. If the LVDS is good, return the T-con and try again. The T-cons are pulls from cracked screen TVs so no-one can be totally sure they are good and many don't bother testing them at all.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

I will try to return the board. Seated the cables many times in case it was the issue, but no such luck. I'll try for another T-CON I guess.

[electronicsurplus]

Re: LG5270 LCD TV - Lines and designs

I agree with Tom66 that the problem is with the T-conn or LVDS cable. you might be able to determine which, in some cases by moving the LVDS cable or wiggling the cable to see if any changes at all.

Also,you can try by heating the board with a heatgun or by placing in an oven @ 300 degrees for 5-10 minutes to re-seat the ic's. but be sure to cover and plastic connectors in aluminum foil with some heatsink compound, if available, to prevent melting. this has worked for me with a few tcons when not available. surely worth the try doesn't cost much

[OldMan]

Re: LG5270 LCD TV - Lines and designs

Which TCON do you think is bad -- the one which gives me the lines shown in my initial post to this thread or the one I now received which gives no color? Both? Or maybe this suggests cables?

[tom66]

Re: LG5270 LCD TV - Lines and designs

Which TCON do you think is bad -- the one which gives me the lines shown in my initial post to this thread or the one I now received which gives no color? Both? Or maybe this suggests cables?

Both. Your original one was bad, and the new one was not tested, IMO.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

Over 1 year and two moves later I've turned my attention back to this TV. Model is 52LG70, not LG5270 as I stated in my first post to the tread.

I've managed to get a working TCON into the set which resolved my lines issue but I have another problem now. The TCON has 4 ribbon cables coming out - two from top and two from bottom which control their respective portions of the screen in a quarter area fashion. When I have the top two ribbons plugged in I get perfect picture on the top 45% of the screen. If I plug in only the bottom two or all 4 I have a totally black picture. I'm envisioning a faulty circuit out the bottom of the TCON to the panel which feeds back and keeps all picture black. Something probably got shaken up during my moves...

Anyone have experience with a 4 ribbon TCON and know where I might check first? I'm hoping I do not have to completely disassemble the set to fix this issue.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

I got bored tonight and went back to this TV....

To update on my last post here is what I've found. If all 4 ribbons are plugged into the TCON the screen is black on start up. Removing each ribbon one at a time from left to right on top and left to right on bottom next, replacing after each before moving to the next I have the following picture displayed with backlight on and volume at all times....

CN4 (top left) = black picture
CN5 (top right) = black picture
CN6 (bottom left) = black picture
CN7 (bottom right) = picture on ~75% of screen with bottom left of screen now being black with a few lines

I've attached pictures to complement what I've written here. Swapping out LVDS cable does not impact what I'm seeing in any case. Nor does a swapping TCON. Both scenarios display the same black screen unless bottom right ribbon cable is unplugged from the TCON board.

Could the ribbon cable that goes from TCON to the panel be the faulty component in this TV? If so, whats the best means of confirming this is the case? How would I find a replacement?

[Clydeuk]

Re: LG5270 LCD TV - Lines and designs

Can you not swap around these ribbon cables to check? Say switch the bottom left and right ones around, do the same tests you mention above and see if the fault moves to the other side? From the pictures they appear to be the same though I can't be sure.

For what it's worth (I hope I'm wrong) I think you have a failure of one of the driver ic's on the bottom right section, removing it's ribbon is removing the problem allowing the remainder of the display to function. That would mean a faulty panel obviously.

Before condemning it might be worth removing any covers that fit over the lower section of the screen (or maybe it's metal frame - depends on panel), you might find a faulty SM capacitor or something else which is dragging the whole thing down. I had this on a large Panasonic LCD where a tiny blob of solder on a capacitor had shorted to the surrounding metal, removing this brought it back to life. I also had a Samsung with a shorted SM capacitor on one of the boards at the top that was the cause of no display but half a display if the ribbon that side was removed.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

Thanks for the advice. I can try to swap ribbons. This was my only thought but didn't want to disassemble entire frame unless absolutely necessary. I will also check out any SM caps while I'm at it.

[OldMan]

Re: LG5270 LCD TV - Lines and designs

Swapped the ribbons and the issue didn't go to the new quarter of screen/board so I've confirmed ribbon is good. Looking at the boards that are tab bonded to the screen I see a lot of green corrosion on the flip up ribbon connectors. Suspecting this may be the issue. Suggestion for how to remove? I tried using eraser and alcohol with qtips without luck. Maybe WD40? If I look for blobs of solder on the SM caps, what will I look for?