LCD-TV repair

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • PowerAmpFreak
    Badcaps Veteran
    • Feb 2010
    • 977
    • Sweden

    #21
    Re: LCD-TV repair

    How is the sequence of changing a CCFL tube?
    By the way, I assume there are several tubes to fill the entire screen, so could one tube fail and the other operate? Or does a faulty tube take the other out as well, because they are parallell connected?

    Comment

    • PlainBill
      Badcaps Legend
      • Feb 2009
      • 7034
      • USA

      #22
      Re: LCD-TV repair

      Originally posted by PowerAmpFreak
      This inverter design uses two transformers on the same board. Each transformer has one single output. Each output is connected to the panel.
      Plainbill, how do you verify the level of high voltage? Do you have a high voltage probe?
      Is lamp failure a common problem, really?
      I don't know what it could be else, if the inverter provide proper HV.
      The only high voltage probe I have was designed to check the high voltage on CRTs. I doubt it would be accurate on the output of an inverter.

      I know nothing about the design of the balancer circuits, but I would think if a single CCFL failed there would either be some sort of error indication or the rest of the lamps would continue working.

      PlainBill
      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

      Comment

      • PowerAmpFreak
        Badcaps Veteran
        • Feb 2010
        • 977
        • Sweden

        #23
        Re: LCD-TV repair

        What I have verified so far, is that inverter starts and runs for two seconds, then shuts off. This must be due to a protection circuit that senses some abnormality. It might be the CCFL current draw which is out of limits.
        I would need a way to verify the status of the CCFL, obviously.

        Comment

        • Tvbob
          tvbob
          • Dec 2009
          • 204

          #24
          Re: LCD-TV repair

          Bud,65 ohms is way to low. Google the number on the inverter transformer to find more info on it. there are a couple good sites on net that sell transformers. (ebay)

          Comment

          • f67bird
            Technician
            • Apr 2007
            • 57
            • USA

            #25
            Re: LCD-TV repair

            Originally posted by PowerAmpFreak
            How is the sequence of changing a CCFL tube?
            By the way, I assume there are several tubes to fill the entire screen, so could one tube fail and the other operate? Or does a faulty tube take the other out as well, because they are parallell connected?
            Most or all of the tv inverters drive each tube individually and have a circuit that detects too much or too little current being drawn in each tube. If one or more tube fails or starts drawing too much current, the inverter will usually completly shut down all tubes.

            Changing one or more tubes would involve taking the panel completly apart and will vary from set to set.
            More common are faults in the inverter itself... which can cause the same symptom.
            Last edited by f67bird; 04-15-2011, 08:54 AM. Reason: misspelled words
            Learner

            Comment

            • alexanna
              Member
              • Mar 2010
              • 1346

              #26
              Re: LCD-TV repair

              ^
              I have read about some LCD TVs that will throw a code for a CCFL out. And continue to light the CCFLs for viewing.
              In any case if you suspect a CCFL problem why not substitute a known good Bulb?
              CCFLwarehouse dose give strike/run voltage,Amprage Ect. On some of the longer CCFLs
              Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

              Comment

              • PowerAmpFreak
                Badcaps Veteran
                • Feb 2010
                • 977
                • Sweden

                #27
                Re: LCD-TV repair

                Originally posted by Tvbob
                Bud,65 ohms is way to low. Google the number on the inverter transformer to find more info on it. there are a couple good sites on net that sell transformers. (ebay)
                Thanks Bob, I will investigate the transformers and check why the secondary measures only 65 ohms. Please note that I got this reading by measuring right across the two high voltage output wires. Measuring only across the CCFL, reads infinite, as it should.

                Comment

                • PowerAmpFreak
                  Badcaps Veteran
                  • Feb 2010
                  • 977
                  • Sweden

                  #28
                  Re: LCD-TV repair

                  The inverter seen in first picture has an external, what it seems, a light detector mounted on the panel. This must be to verify that CCFL comes on or not. In my case, not. I was brave enough to hook up my HV-probe directly on the HV output and could verify something around 2-2.5kV peak which I assume is correct. Still the CCFL won't start.
                  I took the TV completely apart, trying to get into the source of the problem. But it looks like the panel is built as a module (third picture) and won't be possible to split, so I cannot get in touch with the CCFL's. The panel partnumber is shown in the second picture.
                  So I guess this will be the end of this, since I cannot check the lamps, this TV will not be possible to repair.
                  Attached Files

                  Comment

                  • PlainBill
                    Badcaps Legend
                    • Feb 2009
                    • 7034
                    • USA

                    #29
                    Re: LCD-TV repair

                    While I'm sure that Samsung has decreed that "What Samsung has joined together let no man rend asunder", I'm of the opinion someone of sufficient skill can do so successfully. Perhaps close up pictures of the sides of this assembly would yield a clue.

                    PlainBill
                    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                    Comment

                    • PowerAmpFreak
                      Badcaps Veteran
                      • Feb 2010
                      • 977
                      • Sweden

                      #30
                      Re: LCD-TV repair

                      What concerns me, and what tells me this is a "no-go" is that the housing that hides the CCFL has steel rivets which means I must drill all of them out. This will not be economically defendable in my opinion.
                      But for the sake of interest, this would be a thing to do a rainy day.
                      Will provide you with additional pictures in a few days.

                      Comment

                      • PlainBill
                        Badcaps Legend
                        • Feb 2009
                        • 7034
                        • USA

                        #31
                        Re: LCD-TV repair

                        Originally posted by PowerAmpFreak
                        What concerns me, and what tells me this is a "no-go" is that the housing that hides the CCFL has steel rivets which means I must drill all of them out. This will not be economically defendable in my opinion.
                        But for the sake of interest, this would be a thing to do a rainy day.
                        Will provide you with additional pictures in a few days.
                        They sealed it with rivets? That is a dastardly act!

                        PlainBill
                        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                        Comment

                        • alexanna
                          Member
                          • Mar 2010
                          • 1346

                          #32
                          Re: LCD-TV repair

                          Originally posted by PlainBill
                          They sealed it with rivets? That is a dastardly act!

                          PlainBill
                          Wasn't it rivets that broke on the Titanic?
                          Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                          Comment

                          • kc8adu
                            Super Moderator
                            • Nov 2003
                            • 8832
                            • U.S.A!

                            #33
                            Re: LCD-TV repair

                            i would not tear the panel down or give up yet.the ones with 2 leads are what are known as eefl.
                            the way those are used one could die and the others would still light.since by design each are capacitively coupled already they are simply connected in paralell.
                            look back at the inverter.

                            Comment

                            • PowerAmpFreak
                              Badcaps Veteran
                              • Feb 2010
                              • 977
                              • Sweden

                              #34
                              Re: LCD-TV repair

                              Originally posted by kc8adu
                              i would not tear the panel down or give up yet.the ones with 2 leads are what are known as eefl.
                              the way those are used one could die and the others would still light.since by design each are capacitively coupled already they are simply connected in paralell.
                              look back at the inverter.
                              I can't see any problem with the inverter. It generates high voltage and supplies this to the lamps, but the lamps doesn't come on.
                              During each power up, the inverter transformers are driven for 2 seconds, then shuts off. Since the lamps doesn't come on, the light detector is feedback to the inverter board, and shuts it off.
                              I agree with you, in a parallell design one failed lamp would not affect the other. I'm confused.

                              Comment

                              • alexanna
                                Member
                                • Mar 2010
                                • 1346

                                #35
                                Re: LCD-TV repair

                                Originally posted by PowerAmpFreak
                                I can't see any problem with the inverter. It generates high voltage and supplies this to the lamps, but the lamps doesn't come on.
                                During each power up, the inverter transformers are driven for 2 seconds, then shuts off. Since the lamps doesn't come on, the light detector is feedback to the inverter board, and shuts it off.
                                I agree with you, in a parallell design one failed lamp would not affect the other. I'm confused.
                                Have you thought about replacing the 35V 680UF capacitors on the inverter?
                                Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                Comment

                                • PowerAmpFreak
                                  Badcaps Veteran
                                  • Feb 2010
                                  • 977
                                  • Sweden

                                  #36
                                  Re: LCD-TV repair

                                  Originally posted by alexanna
                                  Have you thought about replacing the 35V 680UF capacitors on the inverter?
                                  yes, thought - but never did. Since I saw no obvious sign of problem with them. Do you know this inverter board? Is this a known issue with it?
                                  If this is the solution I'll be ashamed. ...and very very happy!

                                  Comment

                                  • alexanna
                                    Member
                                    • Mar 2010
                                    • 1346

                                    #37
                                    Re: LCD-TV repair

                                    I know of no issues,But at this point you have nothing to loose by trying them.Well maybe 4 bucks.
                                    Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                    Comment

                                    • PowerAmpFreak
                                      Badcaps Veteran
                                      • Feb 2010
                                      • 977
                                      • Sweden

                                      #38
                                      Re: LCD-TV repair

                                      Will be the first thing to do when I see it again!

                                      Comment

                                      • PowerAmpFreak
                                        Badcaps Veteran
                                        • Feb 2010
                                        • 977
                                        • Sweden

                                        #39
                                        Re: LCD-TV repair

                                        Originally posted by alexanna
                                        Have you thought about replacing the 35V 680UF capacitors on the inverter?
                                        Said and done, no improvment after changing the 680uF caps. This one is nagging me. One question, does the CCFL or EEFL lamps turn on directly after supplying HV to them? Or could it take a few seconds?
                                        Why I'm asking is that inverter starts up for one or two seconds, then shuts off. So I wonder if it during this short time has the ability to sense the light by the panel light detector, or if the reason for shut off is that it senses any abnormal current consumption by the lamps.
                                        Or if the HV is out of range, low or high.

                                        Comment

                                        • PowerAmpFreak
                                          Badcaps Veteran
                                          • Feb 2010
                                          • 977
                                          • Sweden

                                          #40
                                          Re: LCD-TV repair

                                          What about taking the light detector off the panel and let an external lamp "simulate" the panel lamps? This would mean the inverter shouldn't shut off due to backlight failure. Maybe this can give me a clue what's going on in there.

                                          Comment

                                          Related Topics

                                          Collapse

                                          • Mirenia
                                            Dell Latitude 7420 - Touchscreen not working since Mainboard replacement
                                            by Mirenia
                                            Hi everyone,

                                            I've got a little "problem child": my Dell Latitude 7420 2-in-1, which had a faulty mainboard.
                                            I replaced it, but ever since, the touchscreen no longer works — and honestly, I’m running out of ideas…

                                            In Windows Device Manager, I just see an I2C HID Device with error code 10. Sporadically, the touchscreen is recognized correctly for just a few seconds, but I haven’t been able to determine under which circumstances this happens.

                                            The touchscreen also doesn’t work in UEFI/BIOS, although it’s enabled...
                                            03-30-2025, 06:47 AM
                                          • orcic
                                            MASTER TL240 and new mainboard LW36BKC01
                                            by orcic
                                            Hello,
                                            I have an old MASTER TL-240 LED TV. Since it stopped working and it had a DVB-T receiver that is being dismissed in Italy, I've decided to replace the mainboard with a DVB-T2 one.
                                            The original problem was that when switching on the TV, the power LED was transitioning from red to steady blue, without showing video or audio.
                                            After checking some voltages on the power supply board (HKL-240101-B Rev. 1.4, HKL from now on) someone suggested me to replace the mainboard.
                                            Now I have some doubts about how to connect the new mainboard to the old power supply.
                                            First of...
                                            05-12-2023, 08:10 AM
                                          • x_orange90_x
                                            Vizio E55-E1 bad backlights or bad inverter?
                                            by x_orange90_x
                                            I just got this tv today and it appeared to have no backlight on. After taking off the rear cover and checking again in the dark I can see that MAYBE one quadrant is lit.. But still it's quite dim. I was going to check the LEDs with my tester, and I found LED 1 and LED 2 + pins on the wire from the inverter, but I couldn't identify a ground. Nonetheless I tried using a mounting screw on the inverter board and also the chassis as ground but regardless my tester reads 300 which is what it reads when there is no voltage draw.

                                            I don't know how exactly to test the inverter itself. Is it...
                                            01-29-2025, 09:24 PM
                                          • Devonavar
                                            Vizio M43-C1 - How closely do I need to match the mainboard number?
                                            by Devonavar
                                            I have a Vizio M43-C1 stuck in a reboot loop with no backlight.

                                            I've tested all the voltage rails coming out of the power supply and they are "normal" for this model (PS_ON & DIM go high when turned on, BL_ON & 3D_ON are close to zero due to backlight power flowing through the mainboard, 5VSB is 5V, and 12V is 19V, which is apparently normal for this board).

                                            Basically, I get similar results to Garry in this post: https://www.badcaps.net/forum/showthread.php?t=80346

                                            So, I've ruled out the PSU for now.

                                            The reboot loop...
                                            08-14-2022, 08:46 PM
                                          • Malva
                                            Problem LG 49UB850V (Mainboard: EAX65684604 / EBT62954607)
                                            by Malva
                                            Hi everyone,
                                            I'm trying to repair my LG 49UB850V TV (WebOS 1.0, UHD model from 2014).
                                            Mainboard model: EAX65684604
                                            PCB marking: EBT62954607
                                            SPI chip: Winbond W25X20CLNIG Problem description:


                                            Originally, the TV would turn on (backlight and LED OK if I force them on), but it shut down as soon as any input was received from the IR sensor or remote. The backlight and power board were working fine.

                                            After testing and verifying the voltages (DRY ON, PWR ON, 12V/24V rails), I suspected a corrupted SPI firmware. What I tried so far:
                                            • I bought another
                                            ...
                                            06-25-2025, 02:07 PM
                                          • Loading...
                                          • No more items.
                                          Working...