Riddled TV Repair Forum

szteven · Joined: 14 Jul 2015 Posts: 3

Hi!

I have an LG FullHD Tv+monitor, model M2794DP. A few days ago it developed an unresponsive rectangular area on the screen, showing only a static colored pattern. Sometimes this area is almost completely cyan, sometimes is almost checkered or dotted. The other part of the lcd screen works just fine. This area grows slowly, it almost doubled its size in 5 days.

Here are some pictures:

What is interesting however, is that if I activate the TV's menu, it displays just fine over this area (hence I think the lcd itself is not damaged):

It has nothing to do with the TV signal, the very same thing happens if I connect it to my PC with a VGA cable and try to use it as a monitor.

Clearly, some circuit has failed. Could you help me to determine which one, so I can buy a replacement? I have some experience in disassembling/repairing electronic devices, I could be able to replace it myself.

Thank you!

Google

kuhurdler · Joined: 28 Dec 2006 Posts: 2879 Location: Overland Park, KS

Remove and reseat the connectors on the T-con.
If no changes, replace the Timing Controller (T-con).
If that doesn't fix it, it is the LCD panel or its tab-bonds and it is a goner.

szteven · Joined: 14 Jul 2015 Posts: 3

Ok, will try what you've suggested with the T-con.

Still, out of sheer curiosity, how could you explain the fact that the faulty area displays correctly the menu items (as it can be seen in the last two pictures)? The signal for displaying the menu doesn't pass through the T-con? Is there a secondary source/circuit for displaying the TV's own menu by overlaying it on the contents?

This is why I think it's not the LCD panel or the tab-bounds. If that was the case, how could it display correctly the menu icons over the faulty area?

kuhurdler · Joined: 28 Dec 2006 Posts: 2879 Location: Overland Park, KS

You have a good point. I stand corrected on suggesting it being the panel. Additionally, It is unusual to see a Tcon fail only part of of the way down, and even more unusual for it to grow as you described. Is this the same for all inputs?

szteven · Joined: 14 Jul 2015 Posts: 3

Success! I've just disassembled the TV, located the T-con, removed the shielding, pressed gently around the ribbon connectors and this did the trick! So it was a minor contact problem.

Here is the T-con board (model LG LM270WF1-TLB1-511 6870C-0252A):

The faulty area (same for all inputs) disappeared, the TV is working as new. Very Happy

I'm still wondering how could it display the menu correctly over the faulty area. The board is connected with two cables on top and one on the bottom. It may be that one of the (upper) cables is for the contents and the other one is for displaying the menu (and everything else not received as an input, but generated by the TV itself)? I don't know which one failed, I touched all the cables and connectors.

Anyway, following your advice, I was able to fix it easily. Thanks a lot, kuhurdler!

Google

kuhurdler · Joined: 28 Dec 2006 Posts: 2879 Location: Overland Park, KS

Glad to hear. Thanks for posting back.