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Old 10-16-2013, 07:10 PM   #1
pc55
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Cool LG 42LGX Mystery Part- at least to me;-)

Greetings all, from a soggy Austin today!

I picked up an LG 42LGX for a few dollars- If the TV turns on, picture will have static-like horizontal lines for a few moments, then goes to full-screen, multi-colored thin Vertical lines for a shorter time, then to a gray screen- not black, as the backlights are still on. Sometimes it goes straight to this screen when turned on. Sound is fine. And once the vertical lines or gray screen appear, nothing can be seen, including the menu.

No obviously bad caps on the power supply or main board- tested the ESR (novice that I am with such tools) on the PS, all seems okay. My next thought is to look at the T-Con board, given the problem. But here is where I find myself in murkier water. There is another board between the Main Board and the T-con board! Part number is EAX41602202 and I had to pry off the cover to even see the board- not screwed on like the other covers I have seen- and the bottom of the board is soldered to another cover.

I have seen this part, after the requisite Google search, referred to as a 'Signal Board' (which I have usually taken as another name for the Main Board with the inputs jacks), or aSub T-Con board.

Can anyone explain to me what this part is and what it does?

Oh- and feel free to tell me if I am on the wrong track here in trouble-shooting this TV- I have done computer tech support for years, but no board repairs beyond replacing a few DC Power jacks- but I hope to learn to do more of this type of repair, on computers and other electronics as I learn- and thank you for this site- I have read posts here off and on for a while now.
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Old 10-18-2013, 03:43 PM   #2
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Here are two pictures displaying this mystery part. On the back of the LCD TV, as most here probably already know, the PS is on the bottom left and the Main Board is on the bottom right, with the circular LG lighted logo/on switch in the center. Just above this circular logo/switch is the mystery board, with the T-Con board at the center top.

Two cables go from the MB to the Mystery Board- the top one looks like an LVDS cable and the other is maybe a power cable? Then you can see two long ribbon cables, different widths by the way, go up to the T-Con board- and two short, identical cables go out the top of the T-Con board to the Driver board for the LCD itself. The other picture is of this mystery board itself, with the perforated top metal shield removed.

Any ideas by anyone on this board?
Attached Images
File Type: jpg LG 42LGX Back.jpg (486.5 KB, 168 views)
File Type: jpg Sub T-Con Maybe.jpg (687.0 KB, 181 views)

Last edited by pc55; 10-18-2013 at 04:15 PM..
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Old 10-18-2013, 03:46 PM   #3
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Oh- and in case anyone else wants to comment on the TV issue itself, here are the first two stages the set goes thru- the static horizontal lines for a few moments (up to 60 seconds), followed by vertical lines over the whole screen- usually more colorful than this picture, and less defined areas- it stays this way for a few moments (maybe 10-30 seconds) before the 3rd stage, a light gray screen (backlight and sound are on).

(I must apologize for the placement of this thread- my computer tech support background gravitated to the 'Motherboard...' threads- but this thread probably should be in the 'Television...' forum- I do not see a way to move this thread however)
Attached Images
File Type: jpg 1-Horizontal Static.jpg (408.7 KB, 111 views)
File Type: jpg 2-Vertical Lines that Follow.jpg (1,022.6 KB, 98 views)

Last edited by pc55; 10-18-2013 at 04:14 PM.. Reason: update
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Old 10-21-2013, 01:52 PM   #4
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Default Re: LG 42LGX Mystery Part- at least to me;-)

I'd talk to these guys if I were you.
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Old 10-21-2013, 03:04 PM   #5
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Thank you Rollme- I had also found a part number not on this board, but that number finds this part in a lot more places- the majority call it a 'Signal Board,' with a couple, like the link you found, as a 'Sub T-Con Board.' I may just email them and see if they can provide an answer, for my own curiosity, since the issue with the TV is most likely the T-Con board itself (I have ordered an inexpensive replacement).

As near as I figure, it's like this model split the normally single Main Board into two separate boards- but why and how the duties are split is what is keeping me awake at nights!

Okay- maybe not, but I would like to know just for the knowledge of it;-)

Last edited by pc55; 10-21-2013 at 03:06 PM..
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Old 10-25-2013, 11:00 AM   #6
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Well, bummer! It was not the T-Con Board. Next step is either the Main Board, or the separate 'Signal Board' that sits between the MB and T-Con Board. I hate to guess, though I lean toward replacing this 'Signal Board' without further info. Unfortunately, I cannot find any bad component on either. If anyone has thoughts, or can help me distinquish the differences between the MB and Signal Board, I would be most appreciative;-)
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Old 10-31-2013, 05:46 PM   #7
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Huzzah! Huzzah! For those who may read this thread in the future, it was that separate Signal Board that was the issue- found a replacement at an okay price, swapped it out, and Voila! a new(ish) LCD to mount on my wall in my work room (or the bedroom formally known as my Daughter's room- Mu-ah-ah-ah-ah-haaa!)

I will keep the bad signal board, and I hope to learn enough to figure out what ails it in the future.
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Old 11-03-2013, 05:33 PM   #8
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Well- I 'Huzzahed' a bit too soon, maybe. the dimly lit gray screen will still show up on occasion, as has a screen with green lines- but this is different- when the green lines show up, they stayed that way until I shut the TV off, unlike the original problem. If I put back in the original Signal Board, the original problem still occurs all the time- put back in the replacement Signal Board, mostly good. And one on, the TV will run for hours without issue.

I put back in the original T-Con board, and that did not help either.

So it appears the original Signal Board definitely has an issue- but there must be a secondary issue as well. I must decide if it is one of the cables or the Main Board now.

GGRRRRR!!!

Last edited by pc55; 11-03-2013 at 05:34 PM..
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Old 11-03-2013, 06:55 PM   #9
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Or maybe the new one is overheating ? Spray it with a cooling spray see if symptoms go away.
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Old 11-03-2013, 07:42 PM   #10
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Default Re: LG 42LGX Mystery Part- at least to me;-)

I did try a bit of coolant (from an upside-down can of Air) already, on the signal board and on the cables on either side of the Signal Board. What makes this harder, since the Signal Board is separate from the Main Board, is that there are two wired cables going from the Main board to the Signal Board (1 LVDS, 1 power, maybe?), and then two Ribbon Cables going from the Signal Board to the T-Con Board (two more LVDS cables, maybe?).

I may just be unjustifiably optimistic it is one of the cables,however- touching or wriggling them has no effect when the TV picture is good, or when it is blank. The more I think about this, the more it now points to the Main Board- but I will have to ponder this some more- and perhaps find guidance from others as well;-)
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Old 11-05-2013, 12:07 AM   #11
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Or could be the panel is just going bad itself. Just looking at the buffer boards on the bottom. Check to see if the ribbons are still ok. There also some on the side. Check those too. Its going to be going to deep into look at this tv. So just do it and see if everything ok.
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Old 11-08-2013, 10:37 PM   #12
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Default Re: LG 42LGX Mystery Part- at least to me;-)

I may take it apart further to look at the tabs- have done so once before for another LCD TV, and one of the tabs bonded between the LCD panel and the Driver board was cracked, and there was a burn mark where it connected to the driver board, probably due to the crack causing a short.

But knowing how fragile these stupid tabs are, I am reluctant to tear the TV apart that far. On the previous set I looked at, there was a thick, black line coming down from the tab- a tell-tale sign of a bad tab. While the LCD could be bad on this set, the symptoms look more like an intermittent signal failure- thus my aggravation that the T-Con and Signal Board replacements did not fix it- at least, not all the way.

Just for my own trouble-shooting, jesselyons2002- any tabs on the side of this set would be from the inverters, correct? And the backlight is fine- it is on even when the screen is a faint gray (no faint picture however). If something was wrong with the inverters tabs, I thought the set, or at least the backlight, would shut off after a few seconds completely. But I am just learning about this stuff, so if I'm wrong, can accept some gentle remonstrance;-)

This weekend, I am going to try to look at the Mainboard again and see if there are any voltage differences from when the TV screen is working to when it is not, and will look at the components again on the mainboard.

Wish this beginner luck;-)

Last edited by pc55; 11-08-2013 at 10:45 PM..
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Old 05-22-2014, 02:19 PM   #13
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Default Re: LG 42LGX Mystery Part- at least to me;-)

I have a LG model 42LG60 with small horizontal lines exactly like the attached images [ 1-Horizontal Static.jpg]
Have someone found the cure to this problem yet.?
The mystery board is called the Digital board.
Please let me know if a solution was found..
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Old 10-11-2014, 09:06 PM   #14
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Well an update- sorry it took so long- I was sick for a few months and had to put aside my new hobby;-)

A summary thus far-
TV is: LG 42LG61
It has three different symptoms that rotate.
Symptom 1: Powers on, picture comes up- but there are flashing white/silver, horizontal lines across the screen- the frequency of the lines dissipates over time. This symptom occurs the most of the three, but not by much.
Symptom 2 Powers on, but black screen- has sound and backlight is on. Usually turning the TV off and on a couple of times resolves this. This symptom occurs second most
Symptom 3: Power on, goes to all fuzzy green screen- you can see ‘shadows’ move in the background from TV program or from opening the TV Settings Menu. Usually turning the TV off and on a few times will fix this- though once, I had to let it sit overnight. This symptom occurs the least of the three

Most of the time (80%, maybe) the TV comes on just fine. I have replaced the TCON Board and the two LVDS cables that go into the TCON Board. I have also replaced the Main Board and the Digital Board (it sits between the Main Board and the TCON Board- a setup not used much, I think). And I replaced all the capacitors on the secondary side of the Power Supply (they all looked good, but were those cheap Samwha capacitors). I also took off the top brackets and was able to inspect and touch the tabs- no effect on the set.

I was surprised it was not the TCON board from all I have researched and read. Any ideas what these rotating, diverse symptoms point to?

Thanks,
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Old 11-02-2014, 06:07 PM   #15
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Hi everyone I am from Mexico city and I have exactly the same issue in a tv set LG 42LG60 and I fix it very easy, the trouble is located on PCB called SUB-TCON part number EAX41602202 capacitors SMD 100uF 16V, 22uF 16V, 4.7uF 35V and 10uF 25V are culprits they not work, I change it all of them and the problema were solved I hope this can help anyone, and thanks for this great fórum...
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Old 11-03-2014, 02:23 PM   #16
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Hi and welcome! I see it is the same part number as the Signal Board on my TV, and I have recently been re-looking at it, since the issues slightly changed when I swapped out this part- both give the silver horizontal lines and blank screen- but the original one had vertical gray lines all the time, while the new one just occassionally has a fuzzy green screen.

Anyway- I could tell nothing from the tops of the capacitors- and I see no way to disengage the board from the bottom metal cover- the top pried off easily enough- but the bottom seems welded on- am I missing something on removing the board from this bottom cover?

Thanks,
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Old 11-03-2014, 10:25 PM   #17
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Hi that part is a Little bit complicated to dissasembly, i used a station desoldering iron to do it and a Little bit more patience but it is possible to do it the idea in fact is leave only the PCB without any shield for easly retire of components by the other hand when I measured the retired capacitors they give me the "right value" according with my capacitometer but my digital osciloscope shows a ripple noise of 800mVpp and that helps me to determinated bad capacitors I suggest to change those capacitors to solve this problem....Greetings from Mexico and is a pleasure can help...by the way an apollogies for my bad english....
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Old 05-12-2015, 05:30 PM   #18
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Quote:
Originally Posted by achavez712001 View Post
Hi that part is a Little bit complicated to dissasembly, i used a station desoldering iron to do it and a Little bit more patience but it is possible to do it the idea in fact is leave only the PCB without any shield for easly retire of components by the other hand when I measured the retired capacitors they give me the "right value" according with my capacitometer but my digital osciloscope shows a ripple noise of 800mVpp and that helps me to determinated bad capacitors I suggest to change those capacitors to solve this problem....Greetings from Mexico and is a pleasure can help...by the way an apollogies for my bad english....
Que tal amigo, tengo el mismo modelo de TV con el mismo problema, y no encuentro los capacitores smd con esos valores en mi país Guatemala, podrías ayudarme y decirme en donde los encuentro en Mexico, Gracias.
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Old 02-02-2016, 10:58 AM   #19
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Default Re: LG 42LGX Mystery Part- at least to me;-)

Quote:
Originally Posted by achavez712001 View Post
Hi everyone I am from Mexico city and I have exactly the same issue in a tv set LG 42LG60 and I fix it very easy, the trouble is located on PCB called SUB-TCON part number EAX41602202 capacitors SMD 100uF 16V, 22uF 16V, 4.7uF 35V and 10uF 25V are culprits they not work, I change it all of them and the problema were solved I hope this can help anyone, and thanks for this great fórum...
but what were the board numbers on each capacitors, theres various numbers at that range of 100uf 16v theres like 9 of them and same as the other caps
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Old 03-08-2016, 11:28 PM   #20
achavez712001
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Default Re: LG 42LGX Mystery Part- at least to me;-)

you need to change all of them specially 100uf 16v.
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