LCD TV "tear down" and fixing (56k)

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LCD TV "tear down" and fixing (56k)

Postby hak8or » Mon Jan 16, 2012 2:31 am

Here is the gallery! http://archive.hak8or.com/projects/Dell_Tv_Fix/

As you all can tell, I have been working on my printer thing lately, which has been going well until I found out that I can't find my working pickit2 anywhere. Well, in the meantime, my girlfriend decided to get rid of her two tv's and a few other electronics, which for me is one of the most awesome things anyone can say, 2nd only to "I'm full, do you want to finish this"? (1) Anyways, back to what I was saying! The lcd's are both not powering up all the way, and the best part is that the lcd's are not cracked. If the LCD is cracked you can pretty much use it only for parts, buying a LCD panel costs more than the entire lcd unit usually, and you can't really fix a cracked LCD. So, with someone helping me carry the HUGE lcd back to my place, we carried it into my basement and I got to work.
(1)http://www.youtube.com/watch?v=ooChw1NLizo 2:00

The one on the left is the smaller Dell, and the one on the right is from a company I never heard of, but it has not bad reviews on amazon so I presume it does not suck and it is worth the effort to fix it.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250671.JPG
Image

First of, the Dell monitor. It is smaller, looks cooler, and seemed like an easier fix. (The big TV did not even have the power light on, the little guy had a power light at least)
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250677.JPG
Image

Side view
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250680.JPG
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Back view
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250682.JPG
Image

Model model for all those interested.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250683.JPG
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Some certifications for the people who want to know. :P
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250684.JPG
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Back of the unit with the back case off.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250686.JPG
Image

Guts!! Left is the power board and the larger right board is the "logic" board. Power boards in tv's usually have one or two large caps rated for 400v+ (Mains rectification) and then a bunch of smaller caps grouped together for each of the voltage rails. Mosfets with large heatsinks are the switchers in these power boards (most are SMPS due to better efficiency), and the yellow colored rectangles are the transformers. The two coils on the bottom of the power board are for (I think) just filtering.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250705.JPG
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Close up of the power board. Nothing seems wrong here, the caps look a TINY bit bulging, but that is pretty much all of them, and I am getting power to the power diode which means the processor is running, so I am guessing the voltage rails are fine. Upon closer inspection with my multi meter and scope it seemed to be indeed running fine.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250710.JPG
Image

The entire thing is insulating with a huge high heat conductivity "mat"! I have never seen such a huge amount used before, especially to insulate the entire board. Instead, I saw it used for heat conducting pads between ram ic's and v'regs in motherboards and graphic cards like the 8800GT, but it was only a small thin sheet.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250712.JPG
Image

One thing that caught my eye was this. It is the board that has audio jacks on the side. I don't know what those inductors are meant to do as I don't dabble with audio, but I presume it is also for filtering? Also, Dell uses LG components in their tv's! I didn't know that!
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250695.JPG
Image

Also, Dell had a really interesting satellite adapter! I still need to check if it is a VGA with some data pins, or just a data connector with a VGAish connector. How nice of them to label the pins though!
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250699.JPG
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Pin labeling
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250698.JPG
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Back of the satellite dongle
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250701.JPG
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Close up of the logic board. I see the genesis chipset very often in flat panels, but as always I can never nab the datasheet on it. I never saw a V chip like that though, bottom right. The satellite dongle is under the metal cover on the top left of the board. Also, you can spot that there is a non connected VGA foot print with its associated passives. I could probably add in the third input if only I had access to the processor on this board.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250708.JPG
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Now, lets get to trying to fix this guy. Here is the left most CCFL PCB, what things do you spot first?
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250702.JPG
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Some charring near the caps, specifically the top left most cap, some charring near the mosfet legs, and only one high voltage wire. I was dumbfounded as to how they got the CCFL's running with a wiring setup like that, as the datasheet for the CCFL driver has a different application circuit than actually implemented, which for me happens very rarely. Edit: Explanation here http://goo.gl/Honjp

Close up on the CCFL driver ic and other circuitry. Upon a closer look, you can notice that they labeled the connectors! That is SO awesome! It made finding out what is wrong infinity easier, and if something goes wrong later, then at least I will have a better idea on what does what so I can quickly find what went wrong.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250703.JPG
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Another angle for the board.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250722.JPG
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When you look closer, it seems like it is just left over flux, but why is it specifically around the components that are interacting with the higher voltages? Edit: Explanation here http://goo.gl/Honjp
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250731.JPG
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The other cap
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250732.JPG
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Something interesting I found while probing around. This is the gate on one of the mosfets for the CCFL driver. 1 us per division and 5 volts per division. Looks normal, right?
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250736.JPG
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Here it is with .1 us per division and I think it was 1 volt per division. I never saw ringing like that before. IT seems to have the first ring right after the gate drops to 0v, a bit of nothing, a sharp ring drop, then another larger ring, then .35 us of nothing again, and then a very large ring out of nowhere, nothing, small ring, then nothing again. Any ideas on why the ringing stops, comes back again, and then stops again? Especially the sudden out of nowhere ring with a huge 2v drop. I am open to any ideas!
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250738.JPG
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How I had it all connected.
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250739.JPG
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After cleaning up the dirty PCB spots and getting rid of the left over flux .... Tadaa !! Of course I had to take a picture of how dangerous prototypes looks on this tv, since I am putting this on the forum. :P Much to my surprise, my contact message thing shows up on the front page of dangerous prototypes! I sent it yesterday I think and after a few hours it wasn't put on the front page nor a response, so I thought it wasn't worth the mention, but I guess I was wrong. :P One LCD down, one more to go!
http://archive.hak8or.com/pictures/Dell_Tv_Fix/P1250748.JPG
Image

I am currently working on putting up a image gallery of sorts on my site (http://www.hak8or.com), I will update my threads slowly with the link to the appropriate image gallery along to where you can get the source code for it. I have used up ten gig of bandwidth this month so far, which is much higher than what I usually get, awesome!
Last edited by hak8or on Mon Apr 06, 2015 9:53 pm, edited 4 times in total.
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Re: LCD TV "tear down" and fixing (56k)

Postby planetjay » Tue Jan 17, 2012 5:56 pm

If you have some links on troubleshooting High Voltage Power Supplies in monitors and TVs, please post. I'm about to reopen my monitor that died. I replaced the caps and it worked for about 2 months. Then it started turning pink and then it started shutting the HV down again. Thanks and gratx on your TV!
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Re: LCD TV "tear down" and fixing (56k)

Postby hak8or » Wed Jan 18, 2012 1:20 am

Are you sure that you did not overlook a blown cap? Maybe another cap was about to fail but showed no visual signs so you didn't replace it. Though, it turning pink is unusual. :P

What I normally do, depending on if I am feeling adventurous or not, is either google the monitor model with the problem I am getting, for example "2232BW flickering" or "2232BW backlight". Usually something shows up and I can get some good information before I tear it apart, so I would know if it is likely to be a quick fix like changing a cap or if it is a horrible power supply problem that could take days to fix. If I am feeling adventurous, I just tear it open and poke around to see what is up. :P A scope is very valuble in these situations since you can check if the PWM ic's are working, then check if the mosfets are actually switching, and later see if there is anything out of the transformer on the board. I have never seen a transformer go bad in anything really, except fly backs when you drive them too hard, but that is a totally different story. :P

Often the PWM ic's have a "fault" pin, if it goes high or low (it says what the fault pin does in the datasheet) then you can get a very good idea of what is wrong. For that you don't even need a scope, just a multimeter.

In the monitors I worked with, there is always a 5v rail, and a 12v rail, and very often some other rails with varying voltage, like the LCD I am working on right now has a 28v rail. If you check each rail with your multi meter and they are getting the proper voltages, then you know it is either the processing board or the power board is not sending out the "Power good" signal.

My information above probably does not help much, so here are a bunch of links like you asked for. :P
http://neoxy-yx.blogspot.com/2011/12/ti ... g-lcd.html
http://www.thice.nl/repair-a-broken-hp- ... baking-it/ <-- you can always try baking it, but I never heard of LCD boards being fixed by baking them.
http://www.geek-republic.com/2011/09/11 ... -1-repair/ <-- SMPS repair
http://g3nius.org/lcd-controller/ <-- would give you a much better idea on the signals in a lcd

I got all of those from searching "repair" on hackaday!
http://hackaday.com/page/4/?s=repair

http://badcaps.net/ <-- the forum on there is very active, and full of good information!

Also, off topic but relevant to my post, here is the gallery to these pictures! It looks really good! :)
http://hak8or.com/projects/Dell_Tv_Fix/

Any feedback is welcome!
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Re: LCD TV "tear down" and fixing (56k)

Postby Pisami » Wed Jan 18, 2012 3:17 am

I have repaired two LCDs, the first one was easy, 3-4 caps and it is working still, 2 years from the repair.

Second one was trickier, because it had external power supply, and as I don't have oscilloscope, I measured the voltage rails with multimeter. However, the multimeter is not fast enough to show the voltage drop, which prevented the screen from starting. Then I opened the power brick, and there were blown caps. Now it works again :)

Edit: pics: http://www.flickr.com/photos/kuvakkeet/ ... 457805926/
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Re: LCD TV "tear down" and fixing (56k)

Postby hardcore » Wed Jan 18, 2012 4:20 am

That 'burning' on the caps and fets, is actually rework (not burnt), either the PCB has been reworked in the factory or in the field.
The 'brown' is a low quality rosin flux that has burned off during the melting of the solder.

I bet that the rework is not RoHS compliant and has used lead solder by the look of the joints, in fact it really looks like a low quality repair as a factory would normally strip the flux using a cleaner.

After running the PCB for a while (unplug) and then just check the temperature on those Ecaps, there may be some HF leakage causing them to overheat, if so they may need replacing.
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Re: LCD TV "tear down" and fixing (56k)

Postby hak8or » Wed Jan 18, 2012 10:49 am

Awesome Awesome pics! Congrats on fixing the Tv's asdf!

Planetjay, I just realized that was your first post! Welcome to Dangerous Prototypes! :)

Hardcore, thank you a huge bunch for the explanation, I will adjust my explanations with your information in mind! How can you tell that the joints are using leaded solder?
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Re: LCD TV "tear down" and fixing (56k)

Postby Pisami » Wed Jan 18, 2012 11:09 am

I didn't think my pictures are that good. Thank you.

As I only have (two) pocket camera(s), and neither is very good, I need to use flash on all of my pictures, any amount of light I can bring to scene other ways is not enough. I don't like the flash burn in the picture, because it covers usually some traces etc. you want to see. The solution is to put white paper in the front of the flash, not too close tough. The number of layers control the light that passes through, and some of the light is reflected to roof and back, so it gives smoother flash. I saw this method in some book or so :)
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Re: LCD TV "tear down" and fixing (56k)

Postby hak8or » Wed Jan 18, 2012 11:21 am

Oh gosh, I thought I was the only one here that constantly fiddles with his/her point and shoot to get rid of the flash problems. :P

The white paper thing I never even thought of! For my camera I usually disable flash and use a tripod, and macro mode has a max shutter speed of 1 second, and I always use 100 iso. But, this time I got too tired with constantly setting up the tripod to get a good angle, so I gave up and used flash.

One thing I want to do is set up a different sort of flash, something like this:
http://hackedgadgets.com/2009/02/06/diy ... lash-ring/
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Re: LCD TV "tear down" and fixing (56k)

Postby ginpb » Wed Jan 18, 2012 3:59 pm

hak8or, do you repair TV/electronic equipment for living?
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Re: LCD TV "tear down" and fixing (56k)

Postby hak8or » Thu Jan 19, 2012 1:11 am

No, I am far too young and inexperienced to do something like that. :P Not to mention I don't know that much about analog electronics, yet at least. I get a massive portion of my stuff from other peoples garbage, which consists of me walking home and finding stuff during garbage day on on curb on the way. If it seems interesting or useful I take it and try to fix it, hence me finding lots of stuff every now and then.

/rant on
If anyone is interested, there is a new law/idea in my city that by 2015, it will be illegal to put your electronics (TV's, computers, toasters) on the curb for garbage day, which will mean that I will loose my main source of electronics. :(
It wouldn't bother me that much but when I found the reasoning behind it I was appalled. They are doing it to apparently "recycle" the electronics and prevent it from going into landfills. If a person wants to throw out that big plasma tv, he/she will have to take that huge item to a special location, god knows how far, and gets no compensation for it. Imagine some poor sap sitting on the bus or train with a big flat panel or vacuum cleaner, taking an hour or two or more away from their time to give that unit, and then getting nothing in return for the time. At least now people like me can actually recycle the things and physically keep the unit out of the land fill! Also, image the increased danger of getting assaulted or robbed if you are walking around with an expensive looking piece of equipment on the way to one of the locations? Also, it ends up in land fills anyways, are they actually planning to try and fix all the electronics people dispose of and "recycle" it?
/rant off

Anyways, yeah, I don't do it for a living. :P I am humbled though that some may have thought that about me!
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Re: LCD TV "tear down" and fixing (56k)

Postby Pisami » Thu Jan 19, 2012 1:24 am

I wish here were piles of "junk" to find parts. No, anything that uses electricity (batteries, solar power, mains...) MUST be returned to place of purchase or special electronics recycle place. And, the recycling is paid in the purchasing price, so don't expect any rewards :D
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Re: LCD TV "tear down" and fixing (56k)

Postby ian » Thu Jan 19, 2012 2:48 am

Also, it ends up in land fills anyways, are they actually planning to try and fix all the electronics people dispose of and "recycle" it?


My understanding is a huge amount is shipped to developing African countries where families live in e-waste dumps and smelt the gold out of ICs in open fire pits. It's not pretty, and the human and environmental damage is immense.
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Re: LCD TV "tear down" and fixing (56k)

Postby sqkybeaver » Thu Jan 19, 2012 9:51 am

ian wrote:
Also, it ends up in land fills anyways, are they actually planning to try and fix all the electronics people dispose of and "recycle" it?


My understanding is a huge amount is shipped to developing African countries where families live in e-waste dumps and smelt the gold out of ICs in open fire pits. It's not pretty, and the human and environmental damage is immense.


this is a huge problem, many companies that advertise cheap/free e-recycling do this, they omit the fact that they ship them and make a killing overseas. i'll gladly pay the $25 at the town recycling center to get rid of that old crt.
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Re: LCD TV "tear down" and fixing (56k)

Postby hak8or » Thu Jan 19, 2012 11:47 am

By landfills I meant either the electronics sitting in a land fill in the States or sent to unfortunate countries where the land is filled with the electronics. But yeah, the smelting process is extremely toxic for the people doing it (often it is the young people) and very, if I have the right idea, toxic to the environment.

A few minutes drive from me is a scrap metal place, and I gave them an air conditioner, a very heavy fully metal cooler, and lots of copper piping, and I only got 15 dollars for all that. But, here is where it gets interesting, the owner lets you walk around and pick stuff out, and if you want it then you either pay for the item in weight or the guy sets a price. I found two LCD's sitting there in the rain, and asked how much, ten bucks each. I ended up not taking them since I wasn't sure if the screen was cracked, but the point is that at least in these private scrap dealers you can walk around and take what you want while paying a somewhat reasonable fee. Once it goes in a city land fill there is no way on earth they will let you in and walk around and pick something out.

Another example is when my school was throwing out their computers. They had maybe a hundred or more of them to throw out, all of them working fine, just needed proper IT people to actually update them and do some virus scans. I was feeling like I stepped on a gold mine, imagine if I could take out many of the power supplies, and I was always in need of extra computers in my house, servers and Nas and whatnot. They were even getting rid of a lot of the flat panels! So I ask a majority of the staff, finding people as high up as I can, if I can nab some, and I was even willing to pay since I know the monitors are working. No, absolutely not, they legally have to dispose of them in a way that the department of education knows that they will be destroyed. Then just don't give me the harddrives, still nope. Some awesome role modeling there! I wonder what the teachers that taught environmental classes would have said about that. The school probably said that because of a legal obligation, which I can't put the school at fault for following it, but it is still frustrating.

Ah dear, there I go again. :P

Anyways, I am currently working on the very large TV, but I have not gotten around to continuing, so I will hopefully upload pictures sooner or later. A power resistor blew on the board (2 holes, charring marks on the board), must have looked awesome when it blew! I am partially color blind so I cannot tell what the resistance was of the resistor originally, but according to what other people told me the colors were, I switched the resistor and it still does not work, I am guessing the blown resistor took some of the mosfets with it. I cannot find the datasheet for the board anywhere, but I found a datasheet for a 2nd revision of the board I think. It looks generally the same, but not quite, and the amount of wires in the connectors differ by one, but at least it gives me a good idea of how the board works. http://www.fspgroupusa.com/fsp2714f02/p/764.html
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Re: LCD TV "tear down" and fixing (56k)

Postby AndThen » Thu Jan 19, 2012 12:36 pm

They do indeed intend for them not to go to the "Local" land fill. Most of the places it is not legal to put them in the landfill there are local "recyclers". If it's not illegal yet where you live you can lobby and they will set someone up with loans and all that tinfoil hat type stuff.

Another example is when my school was throwing out their computers.

You could have tried "Oops I dropped this one i'll just take it up to the dumpster for you.", or asked the guys actually that did the moving =)

I've not seen a resistor fail without cracking. When you say power resistor i picture big ceramic bricks, but those aren't color coded. So it's a larger metal type.. metal-film vs carbon-film? Also if it charred they might be more wrong about the color than you.
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