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    Samsung CCFL to LED conversion

    My 7 year old Samsung CCFL LCD lost the backlight. It would just blink for a moment after turning on.
    I got to this forum via Google and after some tests and measurements suggested in this thread, the backlight started acting moody and I realized that diagnosing and repairing it wouldn't be an easy job.

    But then an idea came to my mind: let's remove CCFL, put the LED strip in and voila - "LED" TV

    Without any research, a couple of minutes later I had this on my table:



    I replaced CCFLs with pieces of LED strip on the same place as CCFLs - 8 rows of them, all connected in series just like if I didn't cut it at all.
    This is the end result.



    With plastic sheets on top, there isn't too much difference when compared to CCFL. Maybe it's not as bright (but I don't have a reference as CCFLs wouldn't stay on), but it's quite good in reality.



    One more...



    I used existing CCFL holes for the power wires.



    Test run proved the concept, but what about turning the LEDs on and off?
    Well, it turned out to be very easy. I first removed HV transformers that used to power the tubes to avoid nasty surprises and used Dremel to cut the power to the entire CCFL HV section which is conveniently marked with a black line on the PCB.
    Then I reused one of the MOSFETs to toggle the power - mainboard pulls the INV_ONOFF line high when powering on the TV, that's connected to the gate and controls the MOSFET. LEDs get power from permanent 13V line that's powerful enough to drive them. Voltage is dropped under 12V with 10 ohm/5 watt resistor which drops it to about 9-10 volts.
    5 watts is too low and resistor quickly gets hot, but it's enough to prove that the entire thing works.



    Close-up of the MOSFET. I cut it from the rest of the circuit as I experienced some weird problems.



    Total cost: ~€20 for 6,5 meters of cool white LED strip and one high power resistor.
    CCFLs are for sale if anyone needs them. I believe that they're OK and that the problem was on the board, but I'll give them for cheap since I can't confirm it. I'm in the EU but I can ship anywhere.

    P.S. Only after I got it working, I searched and found out I'm not the only one with the idea. Why isn't this suggested more often?
    Attached Files
    Last edited by Blagus; 07-30-2016, 03:50 PM.

    #2
    Re: Samsung CCFL to LED conversion

    So what is the Voltage drop on that resistor?
    What the Max current rating of the LED string?
    BTW, the 13V power supply is used for the Audio power amplifiers.
    The pictures looks OK and bright enough?
    As long as the TV is for your own use then it is no problem, different if it is customer's set.
    Last edited by budm; 07-31-2016, 12:17 AM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #3
      Re: Samsung CCFL to LED conversion

      LED strip is rated at 3.6 W/m. I have 5.6 m of it in total, that gives 20,16 W and 1.55 A.
      The resistor has a drop of 3.5 V, so the LEDs get 9.5 V.
      Picture and sound is OK, it could be a little bit brighter but that's probably due to too big voltage drop. That 10ohm/5W resistor is just a temporary solution anyway.

      Comment


        #4
        Re: Samsung CCFL to LED conversion

        Originally posted by Blagus View Post
        LED strip is rated at 3.6 W/m. I have 5.6 m of it in total, that gives 20,16 W and 1.55 A.
        The resistor has a drop of 3.5 V, so the LEDs get 9.5 V.
        Picture and sound is OK, it could be a little bit brighter but that's probably due to too big voltage drop. That 10ohm/5W resistor is just a temporary solution anyway.
        So you have 10 Ohm resistor in series with the whole LED string and the Vdrops on the resistor is 3.5V, that means the current through the LED string is only 3.5V/10 Ohms = 0.350 A (350mA) nothing close to 1.55A and the resistor is dissipating 1.225W so the resistor should be rated at least 3W (you use 5W).
        So how many LED per meter and what is the LED strip Voltage rating based on 3.6 W per meter?
        Can we you provide the link to the site where you get the LED strip from so I can really see what they are?
        Based on 9.5V for the LED that means it has about 3 LEDs at most per set of each LED strip since White LED has Vf of around 3V. It is 12V rating LED strip, right, and it probably already has built-in current limiter for each set of LED? So it looks like the LEDs are not driven at full power but probably fine if the you get enough brightness from them so they will run cooler and last longer.
        for example: 3 LEDs per set and one resistor as you can see in the picture.
        http://www.ebay.com/itm/High-Power-1...3D311665009587

        BTW, you can connect them in series and bypass the resistor so it will be the same about of the LEDs as the original and modify the original drive circuit to lower the drive current.
        Last edited by budm; 08-01-2016, 10:57 AM.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #5
          Re: Samsung CCFL to LED conversion

          Good work, have you a picture of what the image is like ?
          Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

          https://www.facebook.com/Telford-Tel...7894576335359/

          Comment


            #6
            Re: Samsung CCFL to LED conversion

            Originally posted by ReeceyBurger123 View Post
            Good work, have you a picture of what the image is like ?
            I like to know that too since there is no diffuser LENS for each LED any more.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment


              #7
              Re: Samsung CCFL to LED conversion

              Yeah I bet there is going to be light bands and dim patches between the leds in the display. Should have used some ones out of Tv's they work fine.
              Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

              https://www.facebook.com/Telford-Tel...7894576335359/

              Comment


                #8
                Re: Samsung CCFL to LED conversion

                Originally posted by ReeceyBurger123 View Post
                Yeah I bet there is going to be light bands and dim patches between the leds in the display. Should have used some ones out of Tv's they work fine.
                Actually, you can see the bands on the screen shot here:
                https://www.badcaps.net/forum/attach...8&d=1469913643
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment


                  #9
                  Re: Samsung CCFL to LED conversion

                  Originally posted by budm View Post
                  Actually, you can see the bands on the screen shot here:
                  https://www.badcaps.net/forum/attach...8&d=1469913643
                  Ahh yeah I missed that one.
                  Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

                  https://www.facebook.com/Telford-Tel...7894576335359/

                  Comment


                    #10
                    Re: Samsung CCFL to LED conversion

                    Lots of hard work going into that set im considering a ccfl to led conversion on a set with burnt out ccfl might leave it for a while !!

                    Comment


                      #11
                      Re: Samsung CCFL to LED conversion

                      Might be worth playing around with. Strips of LEDs from China can be had for stupid-cheap right now. A couple of those and a variable power-supply, and you're back in business.


                      I can't wait til someone gives me a tv or monitor with bad backlite. Gonna be fun!

                      Comment


                        #12
                        Re: Samsung CCFL to LED conversion

                        @ReeceyBurger123 @budm
                        White patches are visible without LCD panel, but with TV turned on and black image, they're not visible.
                        Since I'm away from home right now and I didn't have time to replace the resistor and my ghetto hacked MOSFET started acting strange quickly, I didn't have time for some extensive tests, but I don't feel like it will be a problem. I'll definitely get back with results once I catch some time.

                        @thosesamsungstho
                        It's actually not so hard. The only hassle is to carefully disassemble everything without breaking the panel. Total time consumed was less than what I would lose with desoldering and testing components which power up CCFLs.

                        Comment


                          #13
                          Re: Samsung CCFL to LED conversion

                          Ok cheers I love a good project like this keep it up and keep us updated
                          Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

                          https://www.facebook.com/Telford-Tel...7894576335359/

                          Comment


                            #14
                            Re: Samsung CCFL to LED conversion

                            Man, I totally forgot about this

                            It's been 3 and a half months since this mod and so far there weren't any problems.
                            Like I said in my previous post, MOSFET started acting very strange, so that part of the board was hacked away too. Energy saving to the max!
                            In the end I used relay to toggle the LED backlight. It's triggered by power on voltage from mobo and it works perfectly. (It's been some time now, I don't remember where exactly I connected it.)

                            I also put 15 or 20W resistor (I don't remember which one), stuck it to the panel's metal frame and put some thermal paste. It can run for hours without any significant heating.

                            Comment


                              #15
                              Re: Samsung CCFL to LED conversion

                              On a dynex 40 i took out the inverter and ccfl's and put leds from a 32 westinghouse on the 24v out (3 strips 6 leds each in parallel with two 150 ohm quarter watt resistors in series). Resistors get a little warm but are good and it has been running for a couple of weeks. It's temporary till a led strip with dim control comes in the mail . When converting ccfl to led the screen will show the led bright spots unless the lights beams are spread by a filter. Otherwise all is good
                              Last edited by Electechj; 04-22-2017, 07:25 PM.

                              Comment


                                #16
                                Re: Samsung CCFL to LED conversion

                                Originally posted by Electechj View Post
                                On a dynex 40 i took out the inverter and ccfl's and put leds from a 32 westinghouse on the 24v out (3 strips 6 leds each in parallel with two 150 ohm quarter watt resistors in series). Resistors get a little warm but are good and it has been running for a couple of weeks. It's temporary till a led strip with dim control comes in the mail . When converting ccfl to led the screen will show the led bright spots unless the lights beams are spread by a filter. Otherwise all is good
                                worse on bright areas
                                Attached Files

                                Comment

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