LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every second.

[Kingfreddie]

Ok.. this is the story:
Have an old Samsung LED 3D TV (UE55F6475). First it started to lose light on the lower 40% of the screen now and then. Like for 10-60 mins and then it would work again. Then a bit later it just got stuck in that position. The lower 40% of the screen is dark, and it gets progressively darker the lower u go so it's obviously that LED strips where not working. I also looked for similar errors online and saw an exact copy and on that one it was faulty LED strips.

This is kinda how it looked, just that mine were at the bottom of the screen:



Just so you know, there were no other cables attached to the TV except power and this problem still happened. I've seen some ppl talking about boxes connected by hdmi etc.. but I just used wifi, no hdmi or dvb cards connected etc. And the fault was there on hdmi and dvb as well.

So I decided to open it to see what was up.

After disassembling (removed the two speakers and the outer layers of the screen, I kept the IR/control connector from the frame connected) and revealing the LED strips I saw that some of the glas beads on top of the LED had came off (3 or 4) but they still seemed to work. My guess is they are just there to either have some function on heat or spreading light?

Anyways, when I reconnected power to check the LED the top 2 rows light up. The rest of them just gave off a short flash every second or so. And I dont know if it's just an illusion but it seemed like the flashing got less bright the lower on the screen u went. On the bottom strip it was hard to notice the flashing.

So to check the LED strips I replaced the top one with a lower one (one that had the bead on a LED fall off). And when it got in the top location it worked fine, and the top strip did not in the lower position.

Now to some technical info: it seems like the LED gets power from 8 pins (4/4 +/-).
On the, I guess, power controller board there is info on how much it should be. Its divided into 4 channels. Ch 1 & 2 and ch 3 & 4. (Ch 1&2 142v/330mah, ch 3&4 214v/330mah )

When I measured measured the voltage on the power controller output connection I got about 50v more than the info printed on the board. One thought I had on this is that it might be due to the fact that I had the light setting on the TV really high.

From there the power goes to a rail where the different channels connect to the LED strips. 2 of the channels have 3 strips and 2 have 2 strips. By the way, when I say strips I mean 2 strips connected together since its a 55 inch TV. Just to be clear, but I dont think that have any implications on the issue.

Each channel seem to have the strips connected in serial.

When I measured the voltage on the top two strips I think o got around 55-60v (it was yesterday so not 100% of the exact voltage, but it was atleast somewhat constant)
But when I measured on the strips that were not working I got really funky voltages.. it jumped all over the place.. but with quite low voltages. It wasn't constant.. it just changed all the time.
I did a resistance check on the rail where the strips connect and at least there is no break anywhere.

I can't understand how there can be voltage on the channels on the output connectors on the PCB but then when they get into the rail it's almost all gone and just jumping all over the place.

If I'm not remembering wrong.. I might be.. the voltage on the faulty channels on the rail seemed to change from + to - on the multimeter.. like it had warped into ac.. but if this isn't indicative of some well known error then disregard it because I might have seen wrong since the numbers changed all the time and I had a hard time holding my somewhat large probes to the correct place.

I think this is all I can think of for now. Please consider I am not a electrician! I have a basic knowledge of 220v AC electrical installation, and some DC low voltage tinkering, but thats it.

So I understand somewhat how electricity behaves but TV repair is nothing I have done before (except a capacitor change, not this tv). So please think of that when replying if I've left out something important or said something stupid.

I would really appreciate your help to fix this TV if it's possible. I have already bought a new one but would like to give this to my mother if it's possible to fix it since she really needs one.

If I need to get new measurements or more pics just tell me where to measure and I will do it. I didn't think of asking on a forum until after I was done trying so maybe I missed some things. And please forgive my English, I'm swedish!

Here are some pics:

[Kingfreddie]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

W8!!! I forgot one very important thing!!!!!

When I measured the voltage on the output led channels from the PCB, and I measured between + and - on the connector, I got the same strange jumping power readings as I got on some of the strip connectors on the rail. But when I measured between the + connector on the output bus and one of the ground screws on the corner of the PCB I got the numbers I mentioned above (about 270v on 2 channels and about 190v on the other 2 channels)

I just remembered this! Wouldn't that imply some grounding error somewhere? Can I just make a new ground for the non working LED channels?

[Kingfreddie]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

Did some more experimentation.. I can't get the LEDs to light up but maybe it's my lack of knowledge.. I just did a simple serial connection at the end of 3 stripes, where they have +/- connections, and connected one end to the 270v on the connector that these 3 were supposed to go to, then I connected the - to the ground screw.

But the only thing that happened was a short weak flash of light from the first led on the chain every time I connected it.

Btw.. do these LED work whatever way u connect -/+ ? Or do they only let through the electricity on way?

Here is a picture anyways.. please don't complain about my soldering, it's a worthless Chinese piece of crap and the tip is bigger Than my little finger.

[cheeky2]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

First off you need to do some reading up on how to test leds. There is plenty information available here and on youtube. Swopping led strips around will do nothing but get you confused and waste your time.
Once you have read up on how to test leds then you will have a better understanding on locating the faulty leds in your strips.
Asking very basic questions means you haven't bothered to try to understand how it works first.

[Kingfreddie]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

First off you need to do some reading up on how to test leds. There is plenty information available here and on youtube. Swopping led strips around will do nothing but get you confused and waste your time.
Once you have read up on how to test leds then you will have a better understanding on locating the faulty leds in your strips.
Asking very basic questions means you haven't bothered to try to understand how it works first.

I have read up on some of it.. but I dont have access to a LED tester.. have ordered one but that will take weeks. And I've also seem the use some batteries to test 1 led at a time. But given the collection of facts I dont think it's the LEDS, if it was why would they work when I change their position on the rail?
The problem must be on the rail or the power controller.

And moving leds I don't see the problem with?

If u don't have access to a tester.. and u have one led channel that works.. why not change one strip at a time to.that channel? When u move one and it stops working u know that there is something fishy in that strip. Kinda seems like an easier n faster solution than testing like 200 leds with a battery if u don't have a LED tester.

And how would that confuse u? Or is 1 strip not the same as another, in that case u could easily mark them? I really don't understand why this would be a bad thing? Can u explain what's bad with it? (I googled and couldn't find anything,)

And if u read my thread it's not really questions about testing leds that's the important question. that I can figure out... its why the LED driver channels behave the way that they do depending on if I put the negative to ground or the negative on the LED power connector for that channel. (,jumping voltage around 0 with changing polarity vs the correct voltage+25% when going to ground)

I also searched and Google the above and didn't find anything. Sure maybe there is a video somewhere on the internet, but I'm not immortal so going through them all will be hard. What I mean is that I couldn't find any title that seemed to adress the issue.

The serial connection I did on the strips wasn't really to check the LEDS but to check the power controller channel that was driving 3 strips and if it was possible when u have it go to ground.

So instead of complaining that I haven't looked enough, when I've spent days going through samsung led repair videos.. that almost all do the same shit, check with led checker, exchange strip, or individual led if they are feeling spicy,.. or just exchange the whole PCB without doing any repair on the board they exchanged. That doesn't really teach anything.

So if u have any ideas why the PCB behaves they way it does please give me some tips. If u want me to take some measurements just tell me where and I will do it.
Driver ch 1 works fine (2 strips). Ch 2 don't, also 2 strips.
Ch 3,4 don't, 3 strips each on them.

I'm quite sure it's not an led issue since it was the lower strips that quit working.. and when I moved the bottom one to ch 1 it light up fine. So its probably in the connections or the power board.

If someone has a video or schematic that explains how samsung gets power to the 4 individual led drivers and what components that are involved it would b great.

[cheeky2]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

How many led TV's have you repaired? None. So your lack of experience is showing.
There are plenty of youtube videos showing you how to test leds in TV's.
It has taken me less than 1minute to find a suitable video here for testing multiple leds at a time:
https://www.youtube.com/watch?v=1n-Nq8HLK20
Without an led tester. Not difficult and can be done with atx power supplies as well.
Why do you think some strips don't illuminate and others do? The current and voltage are monitored by the power board if they go out of tolerance they shut down the output for that output on the leds. How the outputs are arranged in your Tv or the led voltage is unknown to me however the principle in testing leds is the same on any TV.
Do you wish to listen to advice from someone who has extensive experience in repairing LED TV's? Your choice go along whatever route you choose.

[Kingfreddie]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

How many led TV's have you repaired? None. So your lack of experience is showing.
There are plenty of youtube videos showing you how to test leds in TV's.
It has taken me less than 1minute to find a suitable video here for testing multiple leds at a time:
https://www.youtube.com/watch?v=1n-Nq8HLK20
Without an led tester. Not difficult and can be done with atx power supplies as well.
Why do you think some strips don't illuminate and others do? The current and voltage are monitored by the power board if they go out of tolerance they shut down the output for that output on the leds. How the outputs are arranged in your Tv or the led voltage is unknown to me however the principle in testing leds is the same on any TV.
Do you wish to listen to advice from someone who has extensive experience in repairing LED TV's? Your choice go along whatever route you choose.

Didn't I type very clearly in the OP that I didn't have any experience in this area? But advice from someone experienced is only as good as the advice itself.. and "search internet" is not really an advice.. its more a F U.

Atleast in this one you gave a link and some info.. but it seems like u didn't really read any of my post.

U didn't answer whats its a problem to test the strips by putting them on a working channel. It's seems quite logical to me.

And if u had read what I wrote u would know that the problems isn't in the LEDs, it doesn't seem to be atleast. Since they work on the working channel.

That would lead me to suspect that the error is somewhere before the strips. In the rail or the POWER board. That's why I wrote as much info as possible.

I mean if u don't want to help then don't answer.. writing "Google it" is really bitchy. I did as much Google as I could time isn't unlimited.. but as I said if u had read my posts there r things I don't understand that u could explain instead.. but I guess u did a lil of that in the last comment.. if I'm correct in understanding that the reason I get maximum voltage when grouning channels is bcoz PCB will think the LED more power?

[cheeky2]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

Well you know how to try and wind people up I must say that!
You are imagining things and are somewhat delusional stating what you have.
I have never stated I quote you 'I mean if u don't want to help then don't answer.. writing "Google it" is really bitchy. '

I suggest you rethink your thought process and read carefully before making statements that are totally false.

Good luck with the repair of your TV whatever route you choose to take.

No further comments will be made here as it is futile.

[Kingfreddie]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

Well you know how to try and wind people up I must say that!
You are imagining things and are somewhat delusional stating what you have.
I have never stated I quote you 'I mean if u don't want to help then don't answer.. writing "Google it" is really bitchy. '

I suggest you rethink your thought process and read carefully before making statements that are totally false.

Good luck with the repair of your TV whatever route you choose to take.

No further comments will be made here as it is futile.

Did I claim u said "if u dont want to help... etc.."

NO!

That was MY point, that if u dont want to help then just don't comment.

To write: Google it, even if u do it in a paragraph or two, comes off as a bit bitchy and pointless comment. U think anyone dont know google exist? So why say it ? Only one reason, to feel superior.
It's not like u said: Google these key words. That might have been somewhat helpful.

I really don't get why u at all answered here since u have had 0 helpful input, long before u posted the video about non led tester testing I had already posted it wasn't the LEDs.

And u also made a claim about moving led strips for testing that it could be bad somehow.. asked u why, still no answer.

As being totally new here it seems like a lot of elitism shines through in you, I really hope ur from London area since I had a better picture of the northerners.

I can only compare with IT security, my expertise back in the day, or swedish law.. if someone had what I thought was a stupid question I wouldn't answer if I didn't have time.. If I did have time I would EXPLAIN why it was a stupid question and how to proceed correctly, not just: Google it. (Bcoz it usually takes the same amount of time)

And I have yet to understand what was the stupid question in my 3 original posts.. u have given me 0 info except ur second answer that had a little.

And if ur supposed to read the entire internet and know everything before asking, what's the point of the forum?

You seemed more focused on putting me down than helping.
Like "how many TVs have u fixed" , kind of a childish question.

And u say u don't know the voltage etc of the LED on my TV.. its plainly written on the power supply board I attached pictures of, I even wrote it in my post. And if it wasn't that u mean then maybe.. ask?

And u keep on about the LEDS.. if I have tested all the LED strips in the working channel, why do u keep on about the LED?

My point is that's it probably the power control board and that I wanted input on how to test different parts of it.

But I've seen this behavior before on forums.

Ppl that's been there for a long time look down on New members bcoz they see it as a private club. The reddit phenomenon.. its really sad.

And if my last comment "winded u up" .. well I hope u don't go anywhere else on internet.. I'm serious.. the chock could probably kill u.

And yes, since your obviously not interested in helping at all you should have not begun commenting to begin with.. but I guess netter late than never. And I find it kinda sad.. bcoz u probably could have had some useful info if u weren't more interested in putting down the new guy that didn't fulfill your knowledge standard on led tv repair.

[jjanssen7]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

This: "The current and voltage are monitored by the power board if they go out of tolerance they shut down the output for that output on the leds."

I suspect your TV has LEDs that are aged out and drawing too much power. The upper channel tolerates slightly more power than the bottom one. That's why you can move your strips around and get the results you have. That's been my experience with that model anyways.

[Kingfreddie]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

This: "The current and voltage are monitored by the power board if they go out of tolerance they shut down the output for that output on the leds."

I suspect your TV has LEDs that are aged out and drawing too much power. The upper channel tolerates slightly more power than the bottom one. That's why you can move your strips around and get the results you have. That's been my experience with that model anyways.

Thank you for your answer!

That seems logical! The TV was bought new in 2013-14.. and was used until 6 months ago like 18 hrs a day atleast. So that something just snapped is probably likely.

But the two top channels are both 2 strip channels.. while the other 2 are 3 strips. So wouldn't the 2 channels with 2 led strips on them behave rather same? Why would samsung build it so the top one can tolerate more power? Seems like a strange design when u have 2 ch that skall provide power to same amount of led to build them different instead of just copy n paste.. from an engineering standpoint seems strange.

Is it possible to find led strips to this model? I've looked But it seems hard to find.. its just other kind of models.. or can u modify any led strip with the same voltage on the led to fit it?

I read that there are different kind of led that gives you different kind of light. How do you find out what kind your TV has? Now that I think of it there was a small yellow sticker with a barcode on some of the strips.. that might give some answers.

[diif]

Re: LED problem on samsung UE55F6475, 2 strips work. The rest is flashing every secon

Aliexpress for your new LED strips.