LG 42LD550 - Bad main board or T-con

[RodimusPrime98]

I have been researching and troubleshooting my LG 42LD550 LCD issue off and on for the last few months. One day I went to turn on the TV and the only thing it would do is flash the LED light at the bottom of the TV Red. This other thread has a similar issue:
https://www.badcaps.net/forum/showthread.php?t=35304

I measured the following:
12v = 12.33v
3.5v = 3.4v
20v = 20.9v
Pwr_on = 3.2v
Error = 0.7v
P_dim = 2.6v
A_dim = 2.6v
Inv = 0.035v

When I applied an external 3vdc to the INV signal going into the power supply the backlight came on.

I know the other thread resolved the issue replacing the main board but I was hoping someone might have additional guidance on how to repair the main board. Also, is this really the same issue as the other thread? I measured P_dim and A_dim voltages different then they did.

[RodimusPrime98]

Re: LG 42LD550 - Bad main board or T-con

Ok, I gave a solder reflow trick a try as found here:
http://zedic.com/lg-42dl550-fix-repair/

It resolved the red led, it is now blow and the inv line is triggered but now I have vertical lines on the screen. I think I am going to try and bake the main board again and cross my fingers...

Any thoughts to what is causing the vertical lines now?

[tibimakai]

Re: LG 42LD550 - Bad main board or T-con

The re-flow work, may not last and then what you will be doing?

[RodimusPrime98]

Re: LG 42LD550 - Bad main board or T-con

The re-flow work, may not last and then what you will be doing?

Since the reflow only corrected one problem I am hoping that testing other components on the board would lead to the other issue. My post here was in hopes of guidance where to start. These boards are not available anywhere so if I can't fix a component on the board the TV will likely be garbage. I am curious if a crystal or IC got over cooked during the reflow process. Again, I am not exactly sure where to start. Any help is greatly appreciated.

[nomoresonys]

Re: LG 42LD550 - Bad main board or T-con

if you post some pics. you will get more precise help, good luck.

[RodimusPrime98]

Re: LG 42LD550 - Bad main board or T-con

if you post some pics. you will get more precise help, good luck.

Sorry it took so long to reply. Attached are images of what the TV is currently doing. Any help is greatly appreciated. At this point I am feeling as though it is a lost hope.

[saddle_au]

Re: LG 42LD550 - Bad main board or T-con

Is the display static or does it change in any way when you ask for menu or channel change?

[RodimusPrime98]

Re: LG 42LD550 - Bad main board or T-con

Is the display static or does it change in any way when you ask for menu or channel change?

It is not static but fine vertical lines. Very little to no change when pressing menu or channel buttons.

[korff98]

Re: LG 42LD550 - Bad main board or T-con

I also have an LG 42LD550 with a problem. The TV was working fine one night until the X-mas tree timer that was plugged into the same outlet switched off. Instantly the TV turned off. When I tried to turn it on, the red light blinks a few times then goes dark. There is no glow at all on the tv screen. FYI, the tv is not plugged in the timer, but was plugged into a surge protector that was plugged into the same duplex wall outlet as the timer.

I took the back panel off the tv, but none of the capacitors are bulged at the top. Any suggestions of next steps?

[korff98]

Re: LG 42LD550 - Bad main board or T-con

Photos of power board:

[RodimusPrime98]

Re: LG 42LD550 - Bad main board or T-con

Photos of power board:

I would suggest testing the voltages as I listed in the beginning of my post and the post I attached to my first few posts if you are comfortable with that. I chose to tap the lines between the main board and the power supply with the tv running for the most accurate voltages, use the chassis as ground.

[102mm]

Re: LG 42LD550 - Bad main board or T-con

Ok, I gave a solder reflow trick a try as found here:
http://zedic.com/lg-42dl550-fix-repair/

That worked to fix my TV.. that's awesome!!