Announcement

Collapse
No announcement yet.

Hisense 55K20DG LED Voltage questions

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Hisense 55K20DG LED Voltage questions

    Picked up a Hisense 55K20DG from the dump today. screen is good and it powers up and works with no backlight, i can see the image with a flashlight. so i'll assume that i have bad LEDs somewhere.. my question is what is normal range for the LED voltage? the LED power was between 230 and 248V when i checked it.. and is there a way to check an individual LED strip? there are 11 strips in that panel from what i can see.

    Also when i checked the power supply voltages the 16V was running at 19V but the TV was working.. should i be concerned about that too? attached are stock images. If needed, I'll post pictures tonight when i get off.


    Attached Files
    Craigslist Picks & Fixes

    2 ea - Samsung 52"
    Samsung 60"

    #2
    Re: Hisense 55K20DG LED Voltage questions

    "the LED power was between 230 and 248V when i checked it"
    That Voltage looks to be open circuit Voltage due to no load, so more likely the LED string as open connection, the LEDs are connected in series to form one string.
    The filter caps for the LED boosted converter is rated at 250VDC so it is right at the border line, do not run it too long with no load connected.
    The Voltage should be less than that when the LEDs are OK, I expect it to be <200VDC.
    Last edited by budm; 07-20-2015, 02:31 PM.
    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: Hisense 55K20DG LED Voltage questions

      Great! thank you.. I plan on tearing down sometime this week.
      Craigslist Picks & Fixes

      2 ea - Samsung 52"
      Samsung 60"

      Comment


        #4
        Re: Hisense 55K20DG LED Voltage questions

        For same TV, same power supply I got 7 blinks code.

        I checked the board and I found burn signs on SFF1506 (see photo). It seems to be OEM parts and I don't find the dataspecs for it.

        Can somebody help me to identify this diode please?

        Thanks
        Attached Files

        Comment


          #5
          Re: Hisense 55K20DG LED Voltage questions

          Are you getting close to 400VDC between the two legs of the main filter cap? That is the PFC Booster Diode.
          How do the solder joints look on the two solder pads where the legs are soldered to? It looks like flux to me.
          DACO semiconductor, it may not be made any more, not listed on web site:
          http://www.dacosemi.com.tw/exec/prod...TO--220AC&lg=E
          Last edited by budm; 12-03-2015, 10:41 PM.
          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


            #6
            Re: Hisense 55K20DG LED Voltage questions

            Thanks budm for your quick answer

            mesured 387.9 V for C810 and C811

            The solder joints looks good on PFC, but when I opened the tv I found smut on it and it was smelling burn. Also, the legs are black. Do you think I should change it? SFF1006 has the same design, not sure for caracteristics.

            The TV gives 7 blinks when it starts and I can see for short time the start logo. Than with a light I can see image on the screen, but I have no sound.

            what do you think? thanks

            Comment


              #7
              Re: Hisense 55K20DG LED Voltage questions

              How can check the power supply if it gives right voltage? I my case seems to be T-Com or Main board the problem

              Can someone help me with service manual for Insignia NS-55D550NA?

              Thanks

              Comment


                #8
                Re: Hisense 55K20DG LED Voltage questions

                Originally posted by cperiuta View Post
                Thanks budm for your quick answer

                mesured 387.9 V for C810 and C811

                The solder joints looks good on PFC, but when I opened the tv I found smut on it and it was smelling burn. Also, the legs are black. Do you think I should change it? SFF1006 has the same design, not sure for caracteristics.

                The TV gives 7 blinks when it starts and I can see for short time the start logo. Than with a light I can see image on the screen, but I have no sound.

                what do you think? thanks
                The PFC Voltage booster is working and the diode is functioning otherwise you will not have that 387VDC on the main filter caps. You can resolder the legs of the diode just in case it has poor connection.
                I do not know what the 7-blink codes mean.
                Right now we know that you do not have backlights so we need to check the backlights circuit next.

                'my question is what is normal range for the LED voltage? the LED power was between 230 and 248V when i checked it.. and is there a way to check an individual LED strip? there are 11 strips in that panel from what i can see.' So you already tear down the screen to get to the LED strips already?
                Last edited by budm; 12-05-2015, 12:40 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


                  #9
                  Re: Hisense 55K20DG LED Voltage questions

                  Not yet. I checked both caps C955 and C953 and I found different voltage, one was 235-245V and the other 110.8V. That means there are 2 led strings ans I have no load on the first one? what should I check before I tear down it?

                  Thanks

                  Comment


                    #10
                    Re: Hisense 55K20DG LED Voltage questions

                    One thing I never get to see is the whole back side of the TV so I can see how all the boards are connected together, can you take good pictures and upload it?
                    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


                      #11
                      Re: Hisense 55K20DG LED Voltage questions

                      The LED strings inside the panel are connected in series to form one big long string.
                      Have the black probe on the chassis, red probe on the LED connector PIN 1P, turn on the TV and record the Voltage reading and wait for a couple second to see if the Voltage drops down, then do the same again without the LED connector in place.
                      BTW, you can use RED PROBE the positive leg of C955 instead putting at pin 1P. If you look at the board, pin 1P, 1N, and 2P are all connector together.
                      I believe what you are going to see is that you will get the same Voltage reading with or without the LED connector in place.
                      Last edited by budm; 12-06-2015, 12:06 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


                        #12
                        Re: Hisense 55K20DG LED Voltage questions

                        Yes, you're right 1P, 1N and 2P are together. I found 233-245V with/without led connection.

                        So, one led is not working and I have to check all strips. What about the sound?

                        I will tear down the screen today.

                        Thank you budm!
                        Attached Files

                        Comment


                          #13
                          Re: Hisense 55K20DG LED Voltage questions

                          Too bad the OP did not have follow up to show us what he finds inside the panel.
                          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


                            #14
                            Re: Hisense 55K20DG LED Voltage questions

                            I found at least 4 leds burn. Do you have a recomandation where to buy these leds? Do I have to change all leds or it's not necessary?

                            Thanks
                            Attached Files

                            Comment


                              #15
                              Re: Hisense 55K20DG LED Voltage questions

                              I have 6 string in good shape and 5 are not ok. The code that is on the string seems to be OEM. I don't find these on sale.

                              On the label is mention 94V. It think each led should have 3V, 240/77, right? What is 94V stand for?

                              What is your suggestion at this point?

                              Thanks
                              Attached Files

                              Comment


                                #16
                                Re: Hisense 55K20DG LED Voltage questions

                                94V: http://web.rtpcompany.com/info/ul/ul94v012.htm
                                I would try getting new strips, it will not be easy to find.
                                P/N: SVH550AA2_REV05_7LED
                                Last edited by budm; 12-06-2015, 11:10 PM.
                                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


                                  #17
                                  Re: Hisense 55K20DG LED Voltage questions

                                  I don't find this...

                                  What do you think about these?
                                  https://www.shopjimmy.com/samsung-de...face-board.htm
                                  https://www.shopjimmy.com/samsung-de...face-board.htm

                                  Thanks

                                  Comment


                                    #18
                                    Re: Hisense 55K20DG LED Voltage questions

                                    Originally posted by cperiuta View Post
                                    That may work, you just have to do some mod to wire them up the same as original, and when you done, make sure to turn down the backlights level as low as you can but still get good pictures.
                                    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


                                      #19
                                      Re: Hisense 55K20DG LED Voltage questions

                                      Same problem...same tv....leds burnt out....think it almozt started a fire...i can see the image with a flaslight...

                                      Comment


                                        #20
                                        Re: Hisense 55K20DG LED Voltage questions

                                        Did you manage to find new leds. ..sold out at two places i looked at...

                                        Comment

                                        Working...
                                        X