Troubleshooting LCD Backlight Failure Samsung LNT-4066 

Good sir, thank you very much for this video. My LNT-4661 had this exact problem, and I performed your steps identically, and have a working TV again (with the ever so slight dark band). I had purchased an $1800 plasma (decided to buy high end), but can now return it and put my LCD back up, you saved me a lot of money today. Fixed for $75, the cost of a multimeter, soldering iron, and some miscellaneous items.

Followed this to diagnose and repair a Sony Brava KDL 40S4100. It worked just fine. Thanks for the great video and clear instructions. Another TV diverted from the garbage.

Steve, Would be educational to see how to "ring" a transformer like you mention here. Thanks for including us in your "classroom"! Cheers!

Yes I have done that in some sets, this customer just wanted a quick fix and didnt want to spend any money on this set. It was given to them.

Excellent video, thanks. This was exactly the fault on my LE40C650, picture and sound came on initially then picture went blank. Managed to work out which backlight tube was causing the overload protection to shutdown the inverters. Slight complication on my TV in that the inverters drive a pair of tubes as one dual output device. Managed to lift the leads on one of the secondary outputs and insert some insulating plastic film and then bypass its primary side so I did not have to remove the entire inverter. Saved me loads on a new TV, missing backlight barely noticeable.

Great video and great to have somebody on RU-vid that knows what they're doing.

I am sorry but I dont know where you can get new fluorescent tubes also. I would suggest the you find a scrap set with the same size panel and try and replace those tubes. I have had great success with that.

I love these videos. GREAT JOB sharing with us.

thank you for enlighten and you help me a lot to repair my mom tv and save more money to buy a new tv,thanks a lot

LOL wow this was recorded 8 years ago. This tv was probably modern when you made this video.

Excellent video! Thanks! I've been trying to diagnose an older 46" samsung LCD that has backlighting coming on on one side only. Do you think this same issue may be causing it? Or would it likely shut the whole set off, like you mention? I have picture and sound, just very dim on left side (backlighting not coming on). thanks!

MANY MANY THANKS !!!! This tip fixed the TV I was working on Thanks for creating!!!!

I agree most likely main board. Red LED should blink while set is starting but then go out after that.

usually the backlight tubes run from right to left so if one were out it would affect a horizontal band. Dim on one side could a lcd panel failure. Look closely and see if you see shadows when there is moving video. I have had many LCD failures with dim picture on one side.

Great video. I;m also looking how to determine which type of jumper to use.

Based on the ringing test of the transformer and the feedback voltage thats all it could be. The negative lead for all of the voltage measurements was on chassis ground.

Hi and thank you for this informative video. I was able to fix the backlight problem on the Samsung 4061F in part to this instructive video! Much appreciated!

Where do you have the multimeter ground lead connected to? Your testing with the positive lead on the test points but I don't see your ground lead connection.

Samsung LN 5285F. I wanted to try and test my inverter boards using a voltmeter but you never showed where to ground the voltmeter probe just where to test. I have since ordered and received 3 of 4 inverter boards from you ( LL,RL, and RU ). The LU you didn't have in stock. I replaced the 3 boards but made no difference. The original problem was that the tv would boot up, picture would start then drop out. Audio but no video. Not sure where to go from here.

look around the inverter transformers for little blue capacitors, look at the color very carefully and see if if any of them are discolored. I have had a few leaky capacitors and they discolor when they get hot. A good shop should not charge more than $125-$150 on a 32 inch for this repair.

Hello, You said the Florescet tube was bad. How did you test that??? Also when you were testing the transforms,Where did you have your negitive lead?? Thank you again for shareing you knowledge... I've got one that has backlighting problems that I'm trying to fix.... messge me back please, when you get a minute..

If you were trying it time after time the weak tube may have heated up enough to fire. Try it again when its ice cold and see if it gos out again.

Hi again, just would like to say if you keep cracked panels you could use a spare working CCFL from them to replace bad ones and then there would not be any darker line on the screen. Takes more time but looks nice.There is many SONY mostly 40inch LCD TVs that I have fixed that way. Regards

Finally, one good video. Thank you so much!

hi norcal, my 40" samsung has sound and picture, but no backlight. there are no popped/bulging caps on the power supply. after watching this video, i attempted to go through and test the transformers. in the video you have a single test point coming from the two feedback pins. on mine, there is a test point coming off of each one of the 4 pins. so, i put the positive pen on one of the 2 inside testpoints, and the negative pen on the other one of the 2 inside testpoints.(continued)

Just found your channel , thanks a lot ! I wish tho I found this a year ago when I had a set that was doing this (im no expert like yourself) ended up ripping all the bulbs out and replacing them with 600 leds on strips and adding a 12v 2a psu and while it worked , this would have been a lot quicker as it was doing exactly the same thing but I could not for the life of me figure out how to bypass a bulb like that !

Look for FM801 and FM802 on the power supply board, they are small red round fuses. Check them and see if one is blown, if one is bad check the transistors(fets) on the heatsinks nearest the inverter transformer. Chances are they are shorted. better just replace the whole power supply board

Common chassis ground, any metal part like the back of the panel or even the ground on the in/out jacks.

Thankyou, for the advice and posting and sharing your knowledge .. wasn't sure....

Thank you! Thank you! Thank you! This was exactly the problem with my TV. (Well the caps had also gone bad... )

is the dark side a sharp cutoff or is it gradual? If it is gradual then it is most likely the panel, sharp difference between sides could be the tcon.

Awesome details and thanks for that little bypass. I am stuck on one TV right now and was wondering if you knew if this is even an error code or what. I have a Samsung UN60J6200AF and it doesn't turn on AT ALL. I get 6 flashes on the red power LED. The blue light on the LED board remains solid. I also have a solid red led on the mainboard. At first I suspected the power board, but the fuse and capacitors are fine on that. I could not get the LED panel to light up, even disconnecting the mainboard and powering on the system. Before I go any further I just wanted to know if you had any insight on these sets or if you could point me in the right direction.

Good video, but please note this - I followed this video on my LA40A450 and found a high result on #5 from the top. I pulled the transformer off #5 and tried the loop trick. It didn't work on my model. I was going to give in and by a new inverter board but through I'd visually check the CCFL tubes for contact. This video doesn't suggest that step! Yeap, #5 CCFL tube had dropped out of the holder, thus why the high reading and no picture. I re-soldered the transformer back on and all is good.

What is the real fix/solution for this kind of problem ? Why is this one bulb drawing so mush current ? Can one replace the bulb?

I don't have the little silver dots to test this tube resistance as you did. By the way, I have a samsung ln-s4051d. This circuit board on mine is a HI40024WI-B and the slave side -H

May have some smaller bad caps on main board as well

You can disconnect this particular board by just pulling it to the right about 3/8 to 1/2 inch once all the screws have been removed. However even a new board will not fix this set I had because of the internal fluorescent tube failure.

Thank You...Excellent video, very helpful.

Hi I changed power supply but half the screen is a little bit dim. My old power supply worked better than this new one. It showed more brightness on all tv but has a little bit of flickering. Why do you think the problem can be if half the tv is a little bit dim. Maybe motherboard? My other power supply has a dim spot but it was in the left side of the tv now I put a new power supply in and the dim part if on the right side. Please let me know if you can help. Thank you! 😊

Did you make that stand? If so, Can you share how you made it? That would be VERY nice to have and would make things a lot easier!

This is awesome great job of and very informative. Please keep up the great work!!! AWESOME GUY!!

Also want to point out, this tv was free as it was getting thrown out by a family member. I know it's an approx $500 TV, so it could be worth fixing. The smoke thing makes me nervous about having it in my home though. It was a very little bit of smoke and it was white, but still ABNORMAL! What is your expert opinion on what the issue is? I just don't want to get screwed at some tv repair place.

How many LED strips do you think I should use on a 42" to stop the risk of shadowing. I can power the LED's through a plug and socket arrangement with an external supply. So numbers is not an issue for the internal power supply of the TV.

First, I would like to say all your videos are great. You are one one the smartest technicians I have come across on youtube, thanks for all your hard work. I have a dynex dx-46L150A11 and roughly 6 months ago I replaced the backlight inverter board, cuz after 40-60 secs of powering it on I would loose video but not audio. It worked great for the last 6 months and now I'm having another issue. If I power the set on I get the "please wait" message then it goes black but audio works. I did the famous flashlight test and I can see the video playing. So my question is does this sound like the backlight inverter board again? I did a physical check of all the boards and there is no sign of anything burnt out. It just has me puzzled, cuz last time, before I changed the backlight inverter board the video would last 40-60 secs before going black and now it goes black right after the "Please wait" message. Can you tell me what you think? Thanks in advance

thank you for sharing your experience with us!, great explanation, excellent

I was thinking of 1cm (10mm) gap between strips. I am going to buy them on a roll. I have found high bright white ones. Would they be ok. Many thanks for taking the time and trouble to help me. It is much appreciated.

Excellent Video. I did wonder why the tube was not replaced. Is it because it is not possible or incredibly difficult to replace?

Nicely done video, thanks for sharing!

Fantastic! I have a 4661F, very similar TV, with same issue. I followed your approach, with my rudimentary meter, planning on taking the same approach with a cheap solution w/ a jumper. However, as I was testing, on the 2nd/3rd transformer, the TV started working again. What could I have done that would have 'kick started' this? Some sort of short, or something loose that was re-adjusted?

Very nice video it will help my save many TVs.

Great video. I have a Samsung 46" LCD model LN-S45920. The back light is on, as well as the sound...but no picture. Just a warm, glowing black screen. Do you have any idea what might be wrong? Perhaps the T-con card? Thanks for your support. Dan Tietjen

Thanks. I put it back together, and have been using it without an issue for a week or so now. Comes on without issue after being off all day/night etc. I'm certainly not looking over at this gift horse.

Hi i have a samsung le40a556p1f when I turn the tv on it works fine for 2 seconds then the back light goes off i have replaced the inverter board but still no change. Any ideas would be appreciated

can i use this troubleshout method on other inverters too? or only for this inverter?

You can measuring by ring tester if transformers is good or bad for the simple moves

Great video thanks. My problem is a little different. TV is a Samsung LCD LNS4041DX/XAA. When I press the power button, the TV chimes on/off but red LED flashes 4 times and I get no picture OR sound, just black screen. No backlights coming on either and the caps on Power supply board are fine. Which board should I replace? I have some technical knowledge so please help!

where do you connect the other lead of the meter? Only the red lead is shown in the video.

Great video. I have a 46” Samsung LCD. Appears the entire Right backlight is out. How do I troubleshoot this?

Thank you I am guessing I have a similar issue with a Sony Bravia LCD Kdl 32v40300 is the process the same ?my inverter board id different.Thanks

Just from your description sounds like you may have a bad LCD panel, look at my "Sanyo LCD" video and try that

Wow without having the unit in front of me it is very difficult. Start by doing an ohm-meter check of all of the distribution transformers(they should be within a couple of percent of each other)

Sounds like you may have a bad LCD panel itself especially is one side is good and the other side is bad. Most likely not the main board or even the tcon.

Backlights on these go side to side. If you are missing the right half of the image then you have a different problem. Beware of fixit information posted online. You could do damage to yourself or to the set if you are not an experienced technician.

I have a Samsung LNT4669FX/XAA with a dark screen on half of the screen with a little blurring in the dark side of screen! I was given an opinion that it might be the T-con board! What do you think my problem is? Thanx!!!

Where is your meter's black probe connected?

Hi Does this testing procedure hold true for LED tv's as well ? Thanks for the video , wish your shop was close by me :-) The two guys Samsung referred me to carried guns lol....Wanted $150 to drive out to look at the set and the second came out for $100 , didn't open the set up and said it was the Main board and wasn't worth fixing (2 1/2 years old) but offered to buy it from me . A $1300 tv not worth repairing ???

Very helpful.Thanks!!!

My tv is having this problem. How much should I expect to pay if I were to send it to a repair place?

I love your video, Thanks so much for your kindness.

At a TV Repair Workshop you pay for the Specialist knowledge., Same as you do at the Medical Center. Would you trust the Supermarket Checkout Clerk to operate on you or prescribe treatment ? Electrical devices are not to be messed with unless you have the knowledge to diagnose the problem accurately, and skill to effect a repair and maintain safety of the device. Improper repair can become a safety hazard. Cheaper in the long run to have it professionally repaired than screwing yourself.

I m really sorry I couldn't understand the transformer part what did u do how its work, where did u put the other pin of your voltmeter pleas clearify norcal715

I have an LG 50-GA6400-UG Same scenario; picture goes out but the sound works well. I can see the picture in the background with a flash light . The inverter board was replaced twice and both times failed within a week. Could it be something else that is blowing these boards or did I get bad used boards?

excellent video ,,, very smart guy

hi I have a Samsung tv LN-T4066 and the audio do nor work properly sometimes , can you advise me what to do? do I need a new main board? also can you explain to get the main menu to reset my tv settings ?

I have an LN52C530 and my entire backlight has just gone dim (or possibly out), but the TV doesn't shut itself off like the one in this video. That leads me to believes it's not one of the transformers or a tube... correct me if I'm wrong. Any idea what it might be?

Yep I think the backlight inverter is the problem also.

My TV is Samsung ltn4071fx, has and 5 years, 1) when I turn the tv out a red stripe on the left side of the screen when the TV is turned on this time slash disappears. 2) when the TV is turned on about 15 minutes in the red band image is small or hairline but this is displayed in the picture.

I wounder how difficult it would be to replace the CCFL it's self???

Hi- great videos!!! I have a RCA model RLC3708A 37" that is doing the shutdown after powering up the backlight inverter.. the inverter transformers have 5 leads one end & two on the other...The ac voltage at the test points goes to 26 volts before the system shuts off..Can you give me a clue on what to do next. ps. all the backlights turn on momentarily and the red-off , light does not flash..Thanks...

In a response and the iPad app cuts off and sends it. I replaced power supply, no change. All boards appear good with no burns, capacitor bulges or broken solder joints. No clocking/power on/off issues. Sound is good, no backlight though lcd appears functional with flashlight upon close inspection. Used multimeter to rookie test inverter boards. There are 4 leads on the inboard side, 2 on thee outboard side. I tested the outboard side and all report about 343ohms of resistance save one that rea

I am curious about a flickering light issue. The tv works fine, expect for the blinking. Whatever is on, including all inputs, just blinks. I have read an easy fix for similar models that just has you cutting a jumper (jp852/jp854). Does this fix work on the LNT 4066 models? If so, which jumper would I be cutting? Thanks!

Where do you put negative lead when checking ac.voltage on transformers

I have an asus PB278Q 27 inch monitor with a totally with screen display and no video reproduction? Cables are connected nice and tight. Any help?

how am i supposed to remove my inverter? it looks like yours but is feels like its on to something when i unscrewed it and tried pulling it out, I'm guessing that is the backlight bulbs? So I'm sorta stuck here because I don't want to force it so am i supposed to slide it off the black plastic part?

Is the negative lead attached to the frame of the TV?

Is it possible to convert these Samsung TVs to LED back light? If so what is the best source for the kit?

Would this test of backlight work on my Samsung UN55ES6150 Smart TV ?

Thanks so much for your tome

I'll check for the shadows, but I have the back off and verified that the entire left bank of tubes are shutting down after brief power on. Also, mine has two transformers for each tube it looks like.

Took entire tv apart and tested each LED strip. ALL GOOD. Replaced PS board and same result. TV starts up, i see LEDs come on and then go out. Flashing red 2 times and then it tries to start up again and again.... When I disconnect either one of the ribbon cables going from main board to panel the backlights stay on but when I connect both, the less go out. This one has me stumped.. Owner says they were watching tv and it just went out.... Let's see who can solve this one..

hi thanks for reply. i can not see the video of the sanyo how can i get that up. im newish on here. thanks

How do I determine the right gauge/type of jumper to use?

i have a Samsung LCD TV with rainbow colors that appears after 30 seconds or less when I turn it on, anyway to send you pictures so I can show you?

hi I have a veon 50inch model:VN50D3LED. my back lights have gone .if done flashlight test image and sound are their but very dark do use have the part for this or what is the most cost effective way to fix thanks

I have a Samsung 55" Model LN55C630K1F Which the picture only last a few minutes then goes black, still have sound. Help!

Dear I have a panasonic tv model TH -50ph30w. Power light 13 times blinking. Where is the problem? Thanks

Hi, My Proscan 42LA45H has sound but no picture or backlights. I am trying to test the CMO inverter boards 4H.V2308.021 & 031/D2, but the test points look very different to those shown in this video, so I would appreciate some help on testing these boards, thanks a bunch.

Hello Sir need your help I got Samsung LCD Tv model LA40C530 the problem is that Backlight is switching ON for fraction of second and goes off plz suggest me what can i do

Hi, I don´t have any voltage on connector betwen power suply and backligth panel. Capacitors are OK, where can i search for damage? Thanks

My problems are similar, but different. I changed the capacitors on my LN-s4051d. When the tv is on it was working great, but then the backlight died. The LCD works, but the backlight won't fire up. I got mine free too. Amy ideas? I never even get the split second of a flash when it fires up...