LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of green

[bebo]

Hello. First time poster (2nd if you include the introduction post) here. Mechanical Engineer by trade, with a very basic/general electrical background. When it comes to TVs/Displays, I'd consider myself a layman but I learn quickly and understand the basic concepts.

We currently have an HTPC connected to an LG42LD550 via HDMI. The other day the TV lost the signal from the HTPC. Thought the computer just needed to be woken up or restarted. When I restarted, I'd get through the BIOS screen (there were a few pixels that should have been black that were flashing green along with some full screen flashing green going on) and to the Windows 7 splash screen, but after that, I'd get the "No Signal" message on the TV screen. To trouble shoot, here are the things I have tried:

• Different HDMI cable I knew to be good. No change

• Reset the TV settings (don't think this was a factory reset though) with no change. I searched online and found a few potential ways to do a factory reset or access the service menu for LG TVs (hold "Enter" on TV and Remote at the same time, hold "Menu" on TV and Remote at same time), but was unable to access.

• I updated the TV software/firmware to the latest revision via USB with no effect.

• Checked the live EDID with the EDID information in the Windows registry files. They looked the same.

• I WAS able to boot into Safe Mode and get the screen to display correctly (albeit at a lower resolution).

• Updated graphics (Intel HD4000) to the latest revision with no change.

• Reinstalled Windows 7 with no change.

• Connected a 2nd screen (monitor) to the HTPC at the same time as the TV and found that the TV will only display the input signal at 800X600 resolution. Anything higher causes the signal to be lost.

• Connected a separate non-computer/HD input to the TV (Blu-ray drive) and got screen flickering/flashing with some flickering/flashing green splotches (see on this video)

Based on the last bullet, I'm 90% sure it's something in the hardware of the TV. The weird thing is, basic cable TV (coax cable through onboard tuner in the TV) displays just fine, including HD signals. The TV also has a few built in apps like Netflix that also seem to display content just fine. It just appears to be external outputs other than signals that are routed through the tuner.

I read through the general trouble shooting guide in one of the sticky posts and think it COULD be the T-Con, but don't know enough about TV hardware. I'm hoping you guys have an idea or can steer me through some troubleshooting to determine what the issue is. I hear with digital TVs these days, you can sometimes pay someone almost as much to repair the TV as it would cost to buy a new one, so I'm hoping to find a cheaper solution that I can tackle as a DIY project with a little guidance.

Thanks in advance!

Jeremy

[Moreno83]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Hi jeremy ,

I don't think its the T-con as you only have this on HDMI.
Could you remove the shield of the TV and take a picture of the HDMI port?

[bebo]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Hi jeremy ,

I don't think its the T-con as you only have this on HDMI.
Could you remove the shield of the TV and take a picture of the HDMI port?

Not at home right now, but I can. The TV has like 4 HDMI ports (3 on the back and 1 on the side) and the particular port used made no difference in terms of this problem. Does that change your opinion as to what my first step for troubleshooting should be?

[Moreno83]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Also , you don't say anything about different HDMI ports. Looking up this model i get 4 HDMI ports , did you try them all?

EDIT : You were quicker haha , did you try all ports or is it just 1 port?

[bebo]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Also , you don't say anything about different HDMI ports. Looking up this model i get 4 HDMI ports , did you try them all?

EDIT : You were quicker haha , did you try all ports or is it just 1 port?

I believe I've tried 3 of the 4, all with the same result.

[Moreno83]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Ok , the last 1 will do the same so we can rule out dust/bad solder connection.

Im thinking its the chip on the main board that controls the HDMI input. Lets wait for others for their opinion.

[vinceroger69]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

my guess is a seconhand main board will be needed one with the hdmi ports on it when you powered on the pc with the hdmi connected maybe a power surge damaged the board.

[Moreno83]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Yes , I'm thinking the same! The worst possibility will be a second hand main board from Ebay/Shopjimmy.

[Shinju]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Bad mainboard, have you tried 720p and does it look normal?

[bebo]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Yes , I'm thinking the same! The worst possibility will be a second hand main board from Ebay/Shopjimmy.

What's the best possibility?

[bebo]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Bad mainboard, have you tried 720p and does it look normal?

I can't get picture from any thing over 800 x 600 coming from the computer. Is there some way to force 720 p on the TV side via the settings?

[bebo]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

my guess is a seconhand main board will be needed one with the hdmi ports on it when you powered on the pc with the hdmi connected maybe a power surge damaged the board.

So you're saying a surge could have come from the PC over the HDMI cable, or would it have come over the TV power supply?

[Moreno83]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Second hand mainboard from ebay or SJ does not really matter except sj gives warranty i think.

[vinceroger69]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

So you're saying a surge could have come from the PC over the HDMI cable, or would it have come over the TV power supply?

only a guess but from pc down hdmi wire? if you had tv on then powered on the pc?

[bebo]

Re: LG42LD550 not displaying some external inputs at 1080P + flashing/splotches of gr

Yes , I'm thinking the same! The worst possibility will be a second hand main board from Ebay/Shopjimmy.

So it's been about 6 months since my original post. I saw a grand total of 1 mainboard become available on eBay. I purchased it, but it was in worse shape than my original board. Luckily the seller refunded the money after I made a stink.

I've since ordered a new TV, but if I could repaid the old one, It'll give me a second TV to put in another room. Since I can't seem to find any used boards anywhere, does anyone have any experience with sending in boards to a company and having them rebuilt/repaired? If so, can you recommend a site/company?