LG TV video problem. - Page 1
Forum section: electronics / repair

author: Serge125
author_rank: Regular Contributor
timestamp: October 07, 2020, 07:36:23 pm
content: Hi all!!Ok I just got this tv FREE from someone and he did told me of a video problem and even turned it on to show me and yes it does have a problem. He told me that it worked great the night before and next morning this problem. So can this be an easy fix or.... It's an LG 42LV5400-UB. So any thought or suggestions are welcomed!!THANKS ALL!!Serge

author: Serge125
author_rank: Regular Contributor
timestamp: October 10, 2020, 04:17:14 pm
content: Hi all!!Ok here's a video of what the screen does and please let me know if it can be fixed or not, up to now no one commented on this.https://youtu.be/990e7Mn844chttps://youtu.be/W5ZYmxoIDHITHANKS!!

author: Rasz
author_rank: Super Contributor
timestamp: October 10, 2020, 04:46:01 pm
content: tcon or glass itself

author: keymaster
author_rank: Regular Contributor
timestamp: October 10, 2020, 04:51:16 pm
content: There is a big chance , the t-con board is the source of the problem .

author: james_s
author_rank: Super Contributor
timestamp: October 10, 2020, 06:27:11 pm
content: That's what I'd suggest too, if you can find a t-con board for a reasonable price there's probably a 70% chance that replacing it will fix the problem.

author: Serge125
author_rank: Regular Contributor
timestamp: October 11, 2020, 12:30:51 am
content: Ok what would be the 30% part? 😉 THANKS!!

author: james_s
author_rank: Super Contributor
timestamp: October 11, 2020, 04:41:11 am
content: Quote from: Serge125 on October 11, 2020, 12:30:51 amDriver ICs bonded into the glass panel itself, or possibly the main board that handles all the video processing and input switching.

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 11, 2020, 10:21:36 am
content: Check LVDS interconnect between main and T-con all the same.Also check power supply from main is clean when it reaches T-con.I'd say T-con. is defective because the problem is affecting the whole picture (a defective panel will usually have localised defects), the dark trails on green background make it look like a LCD supply voltage on T-con board may be bad.

author: Serge125
author_rank: Regular Contributor
timestamp: October 11, 2020, 09:50:49 pm
content: I’ll check it tomorrow if I have time. There is a 12v on one of the pins but the repair manual doesn’t say so I hope that I’ll be marked on the board.

author: Serge125
author_rank: Regular Contributor
timestamp: October 13, 2020, 05:54:30 pm
content: Ok reopened the rear and this is a 52 pin (very narrow) and nothing is written on what pin does what and even though I do have the repair manual I don't see a 12v just a few 3.3v but how can I check that with the pins so close without touching the other pin close by. Here's where I got the manual if ever someone wants to "guide" me trough the pins.https://elektrotanya.com/lg_42lv5400-ub_chassis_la12e.pdf/download.htmlIt's on page 34 for the LVDS pinout. Page 51 for the 12v but where on that 52 pin is it?? Ok maybe I just got it I'll check later on this. I think it's pin 51 with a few caps, hmmmm....

author: james_s
author_rank: Super Contributor
timestamp: October 13, 2020, 06:35:35 pm
content: I would look for test points nearby, or electrolytic capacitors on the main and T-con boards, those are typically across power supply rails.

author: Serge125
author_rank: Regular Contributor
timestamp: October 14, 2020, 01:16:18 am
content: Quote from: james_s on October 13, 2020, 06:35:35 pmOk I think that I have tracked it down to the t-con 51 pin input from he main board. I have circled it in red and right beside it a fuse, so the 12v comes from main board goes to t-con passes through fuse then to the cap where I should get my 12v, right? And if I do get it then my t-con is the problem because the main is supplying the t-com with the needed 12v and if I get a different reading than the 12v then it's the main at fault.

author: Serge125
author_rank: Regular Contributor
timestamp: October 14, 2020, 06:47:34 pm
content: So am I right with what I said? Just don't want to just probe anything and short it. Oh yeah on the sham there is 3 caps and on the photo I just see one is it because there are other t-con models that has one of the 3 caps? THANKS!! ;-)

author: Rasz
author_rank: Super Contributor
timestamp: October 14, 2020, 07:57:33 pm
content: yes, you can measure directly fuse on the tcon, not that I give tcon supply any significant chance of being the fault here

author: Serge125
author_rank: Regular Contributor
timestamp: October 15, 2020, 07:24:04 pm
content: Quote from: Rasz on October 14, 2020, 07:57:33 pmYep checks out ok for voltage at the T-Con board 11.74v so will order a T-Con tomorrow and hope it will fix this!!Thanks!!!

author: Serge125
author_rank: Regular Contributor
timestamp: October 27, 2020, 06:14:14 pm
content: Hi all!!!Ok I just installed a new t-con same problem!! So what can be causing this problem?? I'm getting the proper voltage to the t-con so it's something else but what any other suggestions?Thanks!!!

author: Rasz
author_rank: Super Contributor
timestamp: October 28, 2020, 12:16:41 am
content: glass itself. Either inside the glass, glass-flex bonding or chip-on-flex TAB driversRussians are the only ones crazy enough to try and fix at this level without access to factory parts and TAB bonding machines.https://web.archive.org/web/20161124102815/http://monitor.net.ru/forum/topic375748-0.htmlTLDR: rip out LED backlight and power supply, those are handy for hobby projects. For example you could turn this dead TV into big light panel. Rest goes into recycle bin.