Repairs to 15.6" LCD/LED Panels (Used in Notebooks) - Page 1
Forum section: electronics / repair

author: LegoLegs
author_rank: Contributor
timestamp: October 11, 2014, 09:03:38 am
content: I have several, different defective 15.6" Laptop Screens (about a 100 - 200) lying around with different faults (No back light, dead pixels, lines, half white displays, half black displays, etc.).I was wondering whether anyone has had any luck doing actual repairs to these type of panels? Not all of the panels I have are from the same manufacturer, but I have at least 10 or so of the same panels of each brand/model if I need a specific component.I'm not really too concerned about back light repairs/replacements - I have the required information to be able to swop back lights if necessary. What I am really interested in, and I don't know whether it is ridiculous or not, is repairs to the "flex PCB" found at the back of all these panels:- Would there be anything that fails a lot on these PCBs?- Is there any way to find schematics for these PCBs?- Any tutorials available for this type of repair? (I searched the web, but only came up with back light repairs and putting pressure on the sides to remove lines..no actual repairs)I should have all the tools available for the job (e.g. ESD safe working area, hot air rework station, soldering irons, etc.) - I just don't know where to start or whether it is even possible to do a repair on these panels (other than back light replacements of course)Thanks :-)

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 13, 2014, 04:36:47 am
content: Sure, just roll one of these into your living room

author: LegoLegs
author_rank: Contributor
timestamp: October 13, 2014, 04:48:20 am
content: Thanks, but that doesn't really help with the questions raised :-)

author: miguelvp
author_rank: Super Contributor
timestamp: October 13, 2014, 05:17:11 am
content: look on ebay for an "laptop lcd controller board" and "laptop lcd controller board programmer" The first one will give you just the controller boards preprogrammed but with the programmer you can change parameters.but you have to do your homework and make sure you get the right programmer for the right controller, on top of that the lvds cables differ from lcd to lcd, so you will have to dig out information, usually on those listings they will have lvds cables as well and if you are lucky with some pinout information.Usually LVDS consists of a differential clock, power grounds, and differential pairs for red green and blue and on higher res lcds it will have additional 3 pairs for extended red green and blue.Most of those controllers ignore the edid, so if you need that you need a controller and cable that can deal with that.There are too many variations for anyone to give you a straight answer, other than do your own research.As for the repair part, other than trying with some of those controllers (usually you can even put the screen you have so they will pair it up with your display) to see if they work, there is not much you'll be able to find from the original manufacturer.For example, something like this:http://www.ebay.com/itm/HDMI-DVI-VGA-Audio-controller-Board-work-lots-of-lcd-Parallel-Port-Programmer-/170940558046But you will need the LVDS cables (and I'm sure these ones won't respect EDID but they might) as they mention on their sale:http://www.ebay.com/itm/9-Kind-LVDS-CABLE-Most-LCD-panel-controller-/170940531610and of course you'll need the inverter if it's cfld backlit.As stated, too many variations and to top it all off, those most likely wont deal with HDCP.

author: LegoLegs
author_rank: Contributor
timestamp: October 13, 2014, 06:09:08 am
content: Quote from: miguelvp on October 13, 2014, 05:17:11 amThanks for the information - LVDS cables & inverters are not an issue, I have several for each type of LCD if required.Basically what I want to do is take all the panels that are exactly the same (model/brand) and repair as many of them as possible - even if that means cannibalizing 50% of them to be able to do so. I have the necessary "jigs" to test the panels on, but aside from "easier" repairs like swopping the back light I am not too sure what else can be repaired on these panels if extra parts are available? My only thought was that possibly there is some component on the PCB that might fail a lot and that someone might have some experience with this?Thanks for all the info so far :-)

author: wraper
author_rank: Unknown
timestamp: October 13, 2014, 06:19:00 am
content: dead rows cannot be repaired as it is usually because of the bonding fault below driver IC die which are usually located on the flex cable between pcb and lcd itself. I can only imagine repairing something on the pcb and replacing backlight. First of all I would check if panel is correctly detected (using external monitor). If not, likely EDID data in the eeprom is corrupted. That would be easiest to repair.

author: miguelvp
author_rank: Super Contributor
timestamp: October 13, 2014, 06:37:37 am
content: One thing is for sure that the boards usually have a ton of test points, and most of the ldc laptop monitors don't even have the EDID pins wired to anything.Old dell one with the LCD board manufatured by NEC, the connector from right to left on LVDS, has 2 grounds then 2 voltages then 4 unconnected (EDID usually goes there I think), then 4 lvds signals three pins each, negative, positive, ground with the last pair being the clock, those are the first 20 connections, the other 13 after those are not connected.I can't see the LCD boards failing much, usually is the invertor or the power supply of the controller. I have that one mentioned that I detached from the actual LCD because I like to play with it to use my scope on high speed signals

author: wraper
author_rank: Unknown
timestamp: October 13, 2014, 07:06:38 am
content: Quote from: miguelvp on October 13, 2014, 06:37:37 amNot true, at least the part about most of. Have not noticed such at all.

author: miguelvp
author_rank: Super Contributor
timestamp: October 13, 2014, 07:32:58 am
content: Maybe it's in the controller and not wired to the actual LCD?But all i've seen it's old stuff so it might be the norm now for all LCD panels, laptop or not, to include EDID at the panel level.

author: LegoLegs
author_rank: Contributor
timestamp: October 13, 2014, 09:35:44 am
content: Quote from: miguelvp on October 13, 2014, 07:32:58 amI have attached some pictures of what these panels look like - they are mostly newer LED panels (no inverter).No screw driver needed to disassemble them - just need to remove some tape. When open you will find the front part (black, "glass" part) is part of the PCB (directly connected) and the back part is the "back light section" with a small cable that fits into the PCB to get power to the back lights. Aside from the swopping the back light part there is literally nothing to repair except if repairs on the PCB might be possible (I've attached a picture of some of the components on the PCB).If repairs on the PCB are not possible I have come to the conclusion that the only step for now might be to identify all the faults on the panels and then repair as many as possible by swopping the front or back section depending on the fault (it is very simple to open and swop either the back light section or glass section). For example - I might have 3 cracked panels with working back lights and 3 panels that are fine except for the back lights - then I just proceed to take the back light sections from the cracked panels and move them over to the panels with dead back lights.It would have been nice if there had been a way to repair some of the "dead line" of flickering issues on some of the defective panels, but repairing 50% is still better than having to recycle them all :-)

author: Rasz
author_rank: Super Contributor
timestamp: October 13, 2014, 10:32:42 am
content: Quote from: LegoLegs on October 13, 2014, 09:35:44 amAlex Eisenhut already showed you what it takes to fix those defects. There is a reason its only economically viable for big expensive panels

author: wraper
author_rank: Unknown
timestamp: October 13, 2014, 10:50:54 am
content: As I said, dead lines are problem with bonding of these ICs. Often you can temporarily restore functionality when pressing them against flex cable with fingers.

author: Zapro
author_rank: Contributor
timestamp: October 27, 2014, 09:46:44 am
content: In my work of repairing laptops, 9/10 times, it's a hairline crack in the glass somewhere, that results dead lines on the display. It's impossible to repair.// Per.