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    Hisense UB50CE591

    Hi guys

    I've been scouring the site looking for info on the above set. Here is my problem. The set powers up and you can see the Hisense logo followed by Smart. It's dim, but it's there. After that, the screen goes dark. I've checked the voltages on both LED connectors. One seems to hover around 120V until the power supply shuts down. The other is around 400V and then shuts down too.
    Are your suspicions LEDs or a power supply/driver issue?

    Appreciate any help you guys can give

    thanks

    greg.

    #2
    Re: Hisense UB50CE591

    You are describing the symptoms of bad backlights. You are 10x more likely to have bad backlights then a bad power supply though bad backlights can damage power supplies.

    Comment


      #3
      Re: Hisense UB50CE591

      Originally posted by greglogan View Post
      Hi guys

      I've been scouring the site looking for info on the above set. Here is my problem. The set powers up and you can see the Hisense logo followed by Smart. It's dim, but it's there. After that, the screen goes dark. I've checked the voltages on both LED connectors. One seems to hover around 120V until the power supply shuts down. The other is around 400V and then shuts down too.
      Are your suspicions LEDs or a power supply/driver issue?

      Appreciate any help you guys can give

      thanks

      greg.
      you have shorted ONE LED BL

      Comment


        #4
        Re: Hisense UB50CE591

        Originally posted by greglogan View Post
        Hi guys

        I've been scouring the site looking for info on the above set. Here is my problem. The set powers up and you can see the Hisense logo followed by Smart. It's dim, but it's there. After that, the screen goes dark. I've checked the voltages on both LED connectors. One seems to hover around 120V until the power supply shuts down. The other is around 400V and then shuts down too.
        Are your suspicions LEDs or a power supply/driver issue?

        Appreciate any help you guys can give

        thanks

        greg.
        Show us good clear pictures of the whole backside of the TV showing all the boards, and good clear straight shots picture of the power supply board.
        Did you test the LED connector Voltage with ref to chassis GND?
        400V reading means the LED power supply is not seeing the load, you have open circuit in the LED string.
        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: Hisense UB50CE591

          Voltage tested across the PS outputs both times at XP901. It's strange because when I swap the connectors around, you can't see the logo on startup, so that's why I was thinking maybe Power Supply.

          Pic of the PSB attached. Really appreciate your help.

          Originally posted by budm View Post
          Show us good clear pictures of the whole backside of the TV showing all the boards, and good clear straight shots picture of the power supply board.
          Did you test the LED connector Voltage with ref to chassis GND?
          400V reading means the LED power supply is not seeing the load, you have open circuit in the LED string.
          Attached Files

          Comment


            #6
            Re: Hisense UB50CE591

            Do you think one shorted and one open on different strings as the voltage is different?

            Originally posted by Diah View Post
            you have shorted ONE LED BL

            Comment


              #7
              Re: Hisense UB50CE591

              Originally posted by greglogan View Post
              Do you think one shorted and one open on different strings as the voltage is different?
              NO, bl work as one circuit to shut down if one of them have issue

              Comment


                #8
                Re: Hisense UB50CE591

                I got this schematic from this site - it's not exactly the same, but it's pretty close. I thought the PS operated both LED strings separately, that's why i was getting different voltages.

                Originally posted by Diah View Post
                NO, bl work as one circuit to shut down if one of them have issue
                Attached Files
                Last edited by greglogan; 08-05-2020, 04:00 PM. Reason: To add attachment

                Comment


                  #9
                  Re: Hisense UB50CE591

                  Originally posted by greglogan View Post
                  I got this schematic from this site - it's not exactly the same, but it's pretty close. I thought the PS operated both LED strings separately, that's why i was getting different voltages.
                  you have SOS shutdown.. both sockets of BL share same IC to control the currents of them.

                  Comment


                    #10
                    Re: Hisense UB50CE591

                    Thank you so much. I'll get some LEDs ordered in the morning

                    Originally posted by Diah View Post
                    you have SOS shutdown.. both sockets of BL share same IC to control the currents of them.

                    Comment


                      #11
                      Re: Hisense UB50CE591

                      they are 3030 6V

                      Comment


                        #12
                        Re: Hisense UB50CE591

                        Originally posted by greglogan View Post
                        Voltage tested across the PS outputs both times at XP901. It's strange because when I swap the connectors around, you can't see the logo on startup, so that's why I was thinking maybe Power Supply.

                        Pic of the PSB attached. Really appreciate your help.
                        The LED drive Voltage is rated at 200V @400mA as printed right on the board, when no load the Voltage will jump high and trips the shutdown circuit.
                        So did you check the good LED in the Diode mode and tell us what you get in both directions?
                        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


                          #13
                          Re: Hisense UB50CE591

                          Thanks @Diah

                          Originally posted by Diah View Post
                          they are 3030 6V

                          Comment


                            #14
                            Re: Hisense UB50CE591

                            Hi

                            I hadn't spotted the voltage quoted, so thanks for that. I'm gonna tear down the rest of this evening and I will report after that.

                            Originally posted by budm View Post
                            The LED drive Voltage is rated at 200V @400mA as printed right on the board, when no load the Voltage will jump high and trips the shutdown circuit.
                            So did you check the good LED in the Diode mode and tell us what you get in both directions?

                            Comment


                              #15
                              Re: Hisense UB50CE591

                              im doing battle with one of these ,
                              see my post from a few days ago same model no led supply volts
                              ive ordered backlight drive/controller ic lx27901
                              as it measures 160 ohm to deck on pin 16 its on the print side of the board,
                              i think when the leds fail they can damage this ic ,

                              so it might be worth you checking yours these ics are only a few quid each

                              Comment


                                #16
                                Re: Hisense UB50CE591

                                Jim

                                can you measure that resistance in circuit or did you de-solder?

                                Comment


                                  #17
                                  Re: Hisense UB50CE591

                                  Originally posted by greglogan View Post
                                  Jim

                                  can you measure that resistance in circuit or did you de-solder?
                                  in situ is fine.
                                  as theres only a cap on this pin which could be responsible .in my case
                                  for me to confirm i de soldered just to be sure before i ordered ic
                                  this pin when tv working normally should have 5v on it and mine had .9v
                                  the 5v is generated inside the chip
                                  if you source any suitable leds please let me know where from , so i can also get some
                                  thanks
                                  Last edited by jimbofz; 08-06-2020, 09:33 AM.

                                  Comment


                                    #18
                                    Re: Hisense UB50CE591

                                    after take the defect LED need to take it in one piece so you can remark the chassis soldering pad of it. there are many 3030 but the pad are different.

                                    Comment


                                      #19
                                      Re: Hisense UB50CE591

                                      Originally posted by greglogan View Post
                                      Jim

                                      can you measure that resistance in circuit or did you de-solder?
                                      hi did you measure pin 16 to deck?

                                      Comment

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