UN40F6300 backlight repair and LED current adjustment UN40F5500

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The video shows the process of replacing single LEDs of the backlight in this Samsung Smart TV.
If you're not sure if your backlight is defective and don't have an oscilloscope the video will show you how and what voltage to apply to which pins in the backlight connector before opening it up in order to test them.
The power supply board (containing the LED driver) is the BN44-00645A. It uses 1 controller chip to drive two different branches of the backlight. One drives 3x13 LEDs, the other one 4x13 LEDs.
The LED current should be decreased after repair. This can be done by increasing two small 1W resistors from 3.6R to 4R7 or 5R6.
When just an LED is faulty without damage to the PCB it can simply be replaced. When the PCB is damaged/burned the whole LED strip can be replaced OR the damaged part can be isolated/cut out and replaced with a piece of another LED strip like in this video : • Easy DIY LED TV backl...
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There are also 2 components in SOD323 packages on the LED strips. These are apparently TVS diodes, marked on the PCB as 12V and 24V.
They are in parallel with their respective LEDs, the larger part of the strip having a 12V and 24V (both in series then in parallel to the LEDs) and a single 24V diode for the shorter part of the strip. They should provide protection against transients to the LEDs. However, when one LED opens , the LED driver will try to increase the voltage (because there is no current) and that will burn these diodes. The 24V marked part starts conducting from 32V in both directions.
The BN44-00645D is slightly different from the "A". Increase the resistance of the 4 4R7 resistors in a 1206 package near the two LED driver chips in a SOIC8 package to lower the LED current. I replaced them with 8R2 resistors.

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11 сен 2024

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Комментарии : 100

@cameronyoung6769 3 года назад

You did a fantastic job with the explanation on how everything works and went into great detail. 2 thumbs up.

@gendragongfly 5 лет назад

Thank you so much for the video, I used it to fix the backlight of my dad's TV. The middle LED strip had one faulty LED. But on the model he has there are no test points on the led strips for testing the LEDs. So I had to take all the little lens caps off and glue them back just to test the LEDs. Anyway, took me 4 hours to fix it, but it's working perfectly now 🙂

@tomtechtod9200 5 лет назад

congrats. next time you can just scratch off a bit on top of the pcb traces leading to the leds, much easier

@songreosmenep 6 лет назад

Very impressed..... Great video....It's also always amazing when you have quality tools to the Job. I thought you handle this repair like a true expert...was a bit hard to follow but I get the point. Cheers!

@convair52 5 лет назад

Thanks Tom for the detailed explanation in this video. I repaired a 40" Samsung TV that keeps blowing the LED backlights that I replaced. It only took 2 days and it blows again. It gave me headache for weeks now for why it keep burned the LEDs and sometimes 1 whole strip.

@tomtechtod9200 5 лет назад

you need to measure the current through them. I usually lower the current via the menu or hardware mod on the driver board and never hear back from them.

@convair52 5 лет назад

@@tomtechtod9200 thanks for the reply. I finally fixed the problem by replacing all the 3 led strips on that tv. And the owner never bother me anymore until now.

@amarjeet_singh880 4 года назад

Good information 👍 nice video

@FantaBH 5 лет назад

I do same as you do , still nice job you have done.

@Vo0d0o2009 3 года назад

you are lucky that the white sheet does not have keep in fire more than this , i actually work on a 75'' same serie , these Fseries have some major fire issues , you should check a video that i have posted year ago , same as your if i remember , if not , its a F serie like your , junction become lose and red hot traces on led strip also sometime become red hot and when it occur it start to flicker as hell ans diodes becomes cooking plate ( red hot) fire caught on white perfored plastic sheet under one or all of this circumstances and fire grow untill it starve of air its a real carnage lol thanks a lot for the current mod idea , im not sure if it also possible to drop led current via service menu on theses series manufacturer have the great idea ( not great at all) to overclock leds on our tvs , ( light brighter /less led /die faster ) in fact leds tv is barely the sheduled obsolecence version 2.0 just to imagine , in service menu most of hisense tvs backlight level is mostly at 255 , drop it to 100 and never a led will burn

@KB1UIF 5 лет назад

Nice Job, very good video, I had a similar fault and the main problem I had was finding suitable LEDs from china etc. The other issue is having a suitable hotplate tool to remove and replace the LEDs with. I got a tiny version from ShopJimmy. Can I ask, where did you find the schematic for your TV that's another issue with many of today's TV's finding the correct circuit diagram. Thanks again.

@canismajor3104 6 лет назад

Very interesting Tom! This is the first video that shows a burned light strip. In my case, the light strip burned on the upper, taller strip trace rather than the small, narrow one. Further, the burn occurred between two LEDs. All 32 LEDs were still OK. Currently troubleshooting my first given-to-me-free-TV. A Samsung UN48J5000. After disassembly, I found a badly-burned spot between two LEDs that would arc, causing the PS to cycle on & off. I attempted a repair by scraping off the white coating and soldering a wire across the burned-out area. Sort of worked. Kept arcing. Burned out the single LED to the right of the burned area. LED ~ 1.4mm/side. Way too tiny to 'replace'. So I figured I'd just cut the end of the strip off with the burned area + dead LED, scrap off the white coating and complete the series ckt with solder. The rest of the LED's all light. Maybe then the PS would stabilize and stay on. PSB is L48MSF_FDY BN44-00852A. LED light strips are 2015 SVS48 FCOM FHD DOE A RIGHT REV1.2 150605 LM41-00120Q_LM4100149A. Curious what causes a backlight strip burn-through between two LEDs that still worked? Very odd. Thanks for posting a video showing this default.

@tomtechtod9200 6 лет назад

Unless a particular trace was designed very narrow to not be able to withstand the current (I don't think so), the only reason I can imagine is a failing solder joint on the LED. The smaller the passage is where the current has to pass the higher the contact resistance and the more this joint will heat. This heat can then propagate away from the failing joint and give the appearance we see in the video. It's the same effect with failing solder joints of through-hole components. But frankly I didn't really care what exactly happened, I only wanted it to work again and prevent it from failing again. The only other thing I could imagine is if the substrate is an aluminum PCB and for some reason there is a short or low resistance path towards the substrate, depending on how the circuit works it may pass current through there. Just a hypothesis though.

@canismajor3104 6 лет назад

Danke Shoen. I can understand burning starting at an LED, but in the middle of a strip between two LED's? That's odd. I do have photos if you're interested. I did cut off the end, connect send & return to complete the series ckt and test. OK. Reinstalled in set. No more zzzt, zzzt pulsing but lower 2 rows of LEDs refused to light. I verified the wiring, connectors from PSB to backlight. OK. So this points to a defective LED driver IC I figure. There are 4 rows of 8 LED's each = 32 total x ~ 3V/Led = 96V needed to turn them all on. (All 32 are wired in series). Obviously the LED driver can't supply that, it protests and is stuck in a start, shut-down, start, shut-down never ending loop. My bench supply won't even allow me to power up two strips in series, much less all four. Still unable to find a SM for either the TV or PS. Also not sure what chassis this unit is. Search hits on UN48J5000 are very rare. Set produced in March 2015. I enjoy troubleshooting as much as you. Deeply curious to figure out problems like this.

@tomtechtod9200 6 лет назад

ok just to get this straight. All LEDs are working now? You can test them either individually or two or more in series only if you don't have a suitable power supply. If the PCB is aluminum, there are no shorts between the aluminum substrate and any of the LEDs right? In this case yes it might be the driver IC. What board is it? What chip did they use?

@canismajor3104 6 лет назад

Originally, ALL LEDs were working. Now I've lost two. One blew after soldering a wire across the burned area in order to bridge it. This LED was the last one on that strip with the burned area, which was about 25mm away. The second one began to blow after experiencing a burned area right at the LED itself, like in your video. This occurred after reinstalling the repaired strip to see if fixing it worked. I powered it up with only 80Vac using a VARIAC as a safety precaution. Good thing I did! I immediately cut power after hearing this second LED begin to arc. I did originally test ALL LEDs using a bench supply per your video. Now I've lost two due to the faulty supply (I suspect). "If the PCB is aluminum...." you mean the light strips? They are very similar to those shown in your video. I included the model # of the strips in my original post, along with the model # of the power supply. Not sure which IC Samsung used as I've yet to ID the IC on the underside. Having a schematic would help as I've not troubleshooted any of these non-CRT TV's. PSB is L48MSF_FDY BN44-00852A. LED light strips are 2015 SVS48 FCOM FHD DOE A RIGHT REV1.2 150605 LM41-00120Q_LM4100149A. Danke.

@tomtechtod9200 6 лет назад

Canis Major you supplied AC to the LEDs? I don't think that's a good idea, we don't know their max reverse blocking voltage... Use only DC.

@ningdeloy6342 5 лет назад

nice video great job ... more video sir

@abdenourderouazi3898 3 года назад

Thanks for sharing the details. I have the same UN40F6300AF and I see a dark horizontal section in the upper of the screen. It’s not blacked out but I can see a difference in brightness. Do you know why would be the problem?

@shadow.banned 3 года назад

I have the same UN46F6300 and the entire bottom of my screen darkened out a year or so back. Eventually, the entire screen died and now it won't turn on. Your problems are the LED strips and/or the power supply board. I would recommend you open it up and search for the power supply board. If you have some dimmed areas, some of your LEDs are out. You could open it up and check them one by one individually with a meter. Then you'd have to learn how to fix the broken ones like this video, or add a jumper cable to skip the broken LEDs. Or you can just buy a full kit online with all strips and replace them. It's pretty easy if you can handle a screwdriver and can manage being delicate with your hands. About ~$100 fix for both. LEDs: Samsung BN96-25304A/BN96-25305A LED Backlight Strips (14) NEW Power Supply board: Samsung BN44-00645D Power Supply / LED Board Power supply board alternative: Samsung BN44-00645A 00645B (KTL SU10054-XXXX) Power Supply / LED Board

@abdenourderouazi3898 3 года назад

@@shadow.banned Actually I did repair it. I bought a complete set of LED lights and changed them. Now it’s working all lit with no shadowed section.

@Vo0d0o2009 3 года назад

did it look like soot ( burnt redidues from post-fire ) ? lol these tv caught in fire behind white sheed and led strips !

@abdenourderouazi3898 3 года назад

@@Vo0d0o2009 Not sure what you meant. Mine did show any traces of burns, either on the LEDs or anywhere else. Bought and replaced the complete set of backlight strips (7). All good now.

@bobbybuckets3113 Год назад

@@abdenourderouazi3898 which led strips did you buy? And are they still working? Looking to replace mine like same as you.

@brettwile8355 3 года назад

Did you have to fix the voltage suppressor?

@bertvisser6423 7 лет назад

A diagram in detail? You don't see that often any more.Where did you find that?

@tomtechtod9200 7 лет назад

you find many schematics on "Elektrotanya".

@chudesnenko 6 лет назад

Thank you for video and for giving voltage details. It's very helpful. It is a very smart way to decrease the current for leds!!!!! Thanks Could you please recommend led brand/model from eBay for Samsung smart TV Un48j523001afxzc backlight? Thanks

@luizpgdm 6 лет назад

Hello, I'm with a Samsung TV UN40F6400. Symptom dark image, backlight and brightness at maximum. Output voltage on drives, three drives measuring 154 Volts, One measuring 48 Volts.

@tomtechtod9200 6 лет назад

Aparentemente na placa BN44-00622A tá escrito Ch1 60V, Ch2,3,4 120V (peguei uma foto da internet). Então parece que as tensoes que está medindo estão mais ou menos normais. A melhor maneira é medir a corrente em cada uma dessas saidas, se tiver LED aberto não vai ter corrente. Se não tiver alicate de corrente, desconecte o backlight e aplique uma tensão direto conforme o que tá escrito na placa (com limite de corrente). Se a placa de fonte te dá tensão mais não tem luz e provável que um ou varios LEDs estejam com defeito. Parece que falta uns acentos no meu teclado, rsrs

@luizpgdm 6 лет назад

Hi. Thank you, my friend.

@tesladude2822 6 лет назад

Great video! I have my neighbors' Samsung UN40FH6030FHZA and I try to repair it. Red light is keep blinking. At first I was hoping on something easy, like a bad capacitor. I checked voltages and I can see all low voltages OK, except that they are on (about 2 sec) and off (about a 1 sec). I do not see any backlights and when I measured voltage on a back light it shows about 345V(max) to ground. As power supply constantly goes on and off, voltage has 345V max and about 290 min, when power supply capacitor discharging (triangle, saw it with my oscilloscope). The voltage should be around 265V. I thought LED circuit is probably open. But then, why power supply is cycling ? Is it really turns power of when LED is broken? Should I try to imitate LED load? I want to distinguish what cause power supply cycling. Bad LED circuit or bad power supply before I will try to get to LED strips. Thank you for any help. BTW, hen I saw you having a diagrams I was so jealous :) !

@tomtechtod9200 6 лет назад

I don't know how the LED voltage in this particular TV is related to ground (chassis). I always measure the voltage that is applied to the LEDs, directly at the connector output. If there is voltage but no backlight at all then the LED circuit is open. Depending on how the LED driver /PSU is made a PSU board could either remain ON, shut down completely, cycle, or even get damaged when the LED strips are defective I suppose.

@tesladude2822 6 лет назад

Thank you

@saarike 7 лет назад

Nice!

@digitalblasphemy1100 6 лет назад

Hey Tom, I have a question about what your television was doing before you knew it was the LEDS. My Samsung 4K LED power light blinks but it comes on. There is not any backlight though so you can only see the screen if you shine a flashlight at the side of it. The television repair man said it was an inexpensive thing but samsung doesn't sell those parts under warranty so they just replaced the television. But they didn't take the old one and I want to repair it myself. Do you have any clue what would cause the entire series of LED lights not to light up??

@tomtechtod9200 6 лет назад

depends on the model. there are always LEDs in series, either all or several. One LED failing open or short can be detected by the LED controller/driver and shut down the hole backlight . It can also be the driver/controller ciruit itself. In a case like yours I always put a voltmeter and current probe on the LED output. If there is voltage (usually marked on the board or if not I just assume a reasonable value) but no current then there is a backlight problem. If there are several strips / outputs and one of them is different than from the others in terms of current/voltage I swap the output to determine if it's the board or the LEDs. Assuming you don't have a current probe or oscilloscope it is pretty hard to actually take reliable and conclusive measurements. I never used a backlight tester or anything like that so can't really say if those work. Also look on the net if others had the problem and a solution for your particular model. A 4K is certainly worth the repair I'd say... Measuring with a multimeter on the PCB output to the LEDs usually doesn't help because it's too slow and the driver will attempt only for a short time to restart ..

@digitalblasphemy1100 6 лет назад

Okay I just bought a multimeter last week and have never used it. Do you think I can use it to diagnose the issue or at least rule out a few things? Thanks so much for you response. I have the model number to the television if that helps. I haven't found anything on google with my specific model but I don't really know where to look other than google. It's a UN55HU6840F made by Samsung

@digitalblasphemy1100 6 лет назад

One more thing, Every 20 seconds or so, A small flicker comes from near the center of the screen. Less than a millisecond so it's hard to see.

@tomtechtod9200 6 лет назад

Yes you can measure at the board output to the LEDs (DC voltage). When you turn on the TV and something happens (voltage goes up) then it's likely the driver is ok and the backlight is faulty. As I said, some TVs start for like a couple of hundreds of ms then maybe try to restart a couple of times and then turn of the backlight driver, so don't expect to measure correct output voltage with a multimeter . usually the output signal is PWM.

@digitalblasphemy1100 6 лет назад

Okay and if the driver is showing a change in voltage, I need to change the LED bulbs most likely?

@Fazwaans 6 лет назад

Thanks for sharing this video , I have same tv with 3 led were not working, i replaced the led bulb and all the leds were working, when i put the led strip back, As soon i connected the led connector same led bulb blow again. Do u think something to do with power supply? Can u kindly help me with this. Thank u.

@tomtechtod9200 6 лет назад

It seems you are not refering to this exact model number. Is it possible that the LEDs in your TV are actually 6V LEDs and you put in a 3V type? Or maybe you put them in the wrong direction, then nearly the entire voltage from the driver would be on the LED, in reverse direction which would surely blow it up... What you describing never happened to me and it is likely that you made a mistake when assembling them...

@manusholm3536 6 лет назад

Hi. very nice video. I have a similar but not identical screen with burnt led's. Will it be possibly for you to direct me to the appropriate current sense resistors on my board? Ill have to order new led strips. i have several burnt and most of the rest of them shows brown spots from the back....so thy did get hot. thanx.

@tomtechtod9200 6 лет назад

what is the exact power supply model number?

@sabrico1918 6 лет назад

Brilliant job Tom , I would like you to help me fix the issue with the TV I got, but before that I want to know if you adjust the LED current will the total LEDs voltage be reduced too? I have Samsung 40 smart TV and the power supply keeps burning the LEDs, it has three strips , LED out put voltage on the power supply board says 151v dc but when I test it with multimeter it givs me 175v, my question if I adjust the current will the voltage be reduced too? and how can I do that? should I search internet for the service manual? but I don't know which resistors have to be replaced, can you help me please? is there a simple way to know which resistors for all kinds of TV's power supplies? my TV model number is UN405203, I hope you help me as soon as possible, best regards

@tomtechtod9200 6 лет назад

I don't know this model. I'd say voltage will remain more or less the same. Average current and therefore power dissipation for the LEDs will decrease when increasing the resistance value of the resistor that is used to measure the LED current. Usually it is just PWM switching a MOSFET in series with the LEDs. The resistor is usually a few Ohms, could be a couple in parallel and it is also in series with the LEDs. You can also have more than one LED driver , either from one IC or several ICs... Quite some variation. On some TVs adjusting the current will indeed adjust the voltage with a boost converetr, have seen that on RCAs.

@sabrico1918 6 лет назад

TomTechTod Dear Tom, first of all, I would like to thank you for responding to people and helping us, we are all appreciate your time and help, would you mind helping me more if I give you the model number with a focused picture of the power supply? is it possible to contact you over an email?

@kevinjames1587 6 лет назад

where are these led drivers you speak of? I have sound, no picture. Good power on psb, main, and t con. Next about to check led strips...

@tomtechtod9200 6 лет назад

it's a SMD chip on the bottom side of the psu board. it is very likely that the problem is with the LEDs though

@luca.holanda 6 лет назад

Nice video! Do i still have to adjust the resistors if i change the whole led strip?

@tomtechtod9200 6 лет назад

Lucas Holanda I would either adjust the resistors or the backlight in the menu (for each source). A new LED strip isn't any better than the original one so at full backlight intensity they'll gonna be damaged again, sooner or later.

@luca.holanda 6 лет назад

Could i just jump the burnt LED as a provisory fix? The other leds on the strip would light up, right?

@tomtechtod9200 6 лет назад

Lucas Holanda that depends on the LED driver circuit. Some are able to detect that condition and shut down. Ideally you would use some normal diodes in series instead of the burned LED.

@duanejudson209 6 лет назад

I have a Samsung 46" LED UN456h6201afxza BLACK SCREEN With sound i have watched several of your videos and i have a question. I tested the LED jack on the power board and i get M1+ 288v, M1- 267v, M2+267v, M2- 250v, M3+ 250v, M3- 225v, M4+ 228, M4- 07, this is with the TV on and the LED wire connected can you help me figure out where the problem is. I think it is the back light and or the power supply but i am getting conflicting information. MY THE WAY LOVE YOUR VIDEOS.

@tomtechtod9200 6 лет назад

1. What is the reference for your measurements/where did you connect the "-"probe of your multimeter to? You should be measuring with one probe on Mx+ and the other on Mx-. You do seem to have a high enough voltage on M4+/-. 2. What is the board number? The one I found for this TV does not have M1 M2 etc. (BN44-00771A) 3. How many wires are on the LED connector? 4. If there are more than two wires on the LED connector: Are they interconnected via traces on the PCB? This would be near/at the LED connector on the PSU.

@kennethpappas 5 лет назад

i have backlight but no picture. replaced all 3 boards and same problem. what might be the fault?

@tomtechtod9200 5 лет назад

are we talking about the very same TV ? same model number?

@kennethpappas 5 лет назад

@@tomtechtod9200 Yes.

@MrElgato11 6 лет назад

Hi do you have the item number for the led strip for this tv I have the same one

@tomtechtod9200 6 лет назад

It's in the video at 5:35.

@DomenM 5 лет назад

HI, is there a way to repair a cracked screen on this model tv ? Thank you.

@tomtechtod9200 5 лет назад

You can replace the whole screen, yes. It's definitely not worth it though.

@DomenM 5 лет назад

@@tomtechtod9200 Thanks. I have found a new use for it. I have removed the front LCD panel. I have now a huge bright LED panel light :)

@durgasherya3531 4 года назад

Which instuments useing name of instuments his it in india

@durgasherya3531 4 года назад

Pl reply me

@tomtechtod9200 4 года назад

I don't know what instrument you mean. Oscilloscope? Multimeter? Current probe?

@durgasherya3531 4 года назад

@@tomtechtod9200 oscilloscope what is that pl show me photo iknow multemeter

@durgasherya3531 4 года назад

@@tomtechtod9200 sir also one video dvd push power proublem repair

@tomtechtod9200 4 года назад

This was a fluke 123. You don't necessarily need an oscilloscope for the repair

@marcosmenezes9455 6 лет назад

Correct led in Aliexpress.

@thebighat99 4 года назад

I need to know what SOD323 TVS diodes to get for replacement? 12v and 24v what are specs? The 24v one has 4E BA on it. This a great video it helped me a lot.

@tomtechtod9200 4 года назад

If they aren't shorted I wouldn't bother replacing them. If they are shorted any tvs rated for the right voltages with the right footprint will do.

@thebighat99 4 года назад

@@tomtechtod9200 So someone told me the 4E stands for cmosh-4e just in case someone else need to know. Thank you for the help.

@tomtechtod9200 4 года назад

Hum. Not sure about that. The part number you mention is a 40V Schottky diode, not a TVS

@shadow.banned 3 года назад

@@thebighat99 Did you ever figure out which TVS diodes to get?

@thebighat99 3 года назад

@@shadow.banned no am not sure witch diodes to get. I going to get some of cmosh-4e, and some standerd diods. but you know I just want to put right ones in, I would like it to be safe. you want the specs to match. If you find out let me know. :).

@djordjelukovac8041 5 лет назад

You need to replace all leds.

@tomtechtod9200 5 лет назад

No you don't. You "can" do that. You "have to" lower the LED current though.

@djordjelukovac8041 5 лет назад

@@tomtechtod9200 You must or you will open your set every time each led dies.

@tomtechtod9200 5 лет назад

@@djordjelukovac8041 if you lower the LED current to a maximum of 75% or less no other LED will fail. Doing this repair and continue with high current is pointless. But do as you wish.

@djordjelukovac8041 5 лет назад

@@tomtechtod9200 I agree for led current.

@djordjelukovac8041 5 лет назад

All of those leds have equal working time. Of course you need to lower backlight brightness to be lower then 50,but after replacing all leds. Trust me ,customers do not listen ,they will turn that up to 100%.