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Polaroid tql39r4pr002 TV switch off after logo display

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    Polaroid tql39r4pr002 TV switch off after logo display

    Hello,
    i have an issue with my polaroid TV Model : tql39r4pr002
    the standby led is red , and when i turn on the TV it shows the polaroid logo and turns off, also the standby led switches to blue the back to red .

    capacitors are apparently ok, i have 320V in the smoothing primary capacitor, and 13V in the diodes in the secondary.

    i don't understand why the mainboard switches to this mode and don't turn on.

    don't find any service manual for this model ,or the main board schematic. cv9203h-a42

    thank you for your help.
    Attached Files

    #2
    Re: Polaroid TV switch off after logo display

    sounds like it maybe a firmware issue after looking into a couple of threads using your mainboard number what is the lcd panel number used in this tv (usually on a white sticker on tv metal chassis)

    Comment


      #3
      Re: Polaroid TV switch off after logo display

      thank you vinceroger69,

      here what i found on the chassis (see attached picture) :
      HK385LEDM-AH5BH.

      how can i update the firmware as i can't turn the tv on ?

      thank you for your help
      Attached Files
      Last edited by coax81; 08-13-2020, 09:57 AM.

      Comment


        #4
        Re: Polaroid TV switch off after logo display

        should i update the firmware ? where can i find this firmware , on the polaroid support website i didn't find it !

        Comment


          #5
          Re: Polaroid TV switch off after logo display

          i tested the voltage on cables connected to the Backlight LEDs (PJ8 and PJ7 connectors) and on standby i have 26 v , but when i push the On button it raises quickly to 40v then goes back to 26v .

          is that symptom of backlight issue ? or something bad on the board ?
          Attached Files

          Comment


            #6
            Re: Polaroid TV switch off after logo display

            "is that symptom of backlight issue ?"
            Yes.

            Comment


              #7
              Re: Polaroid TV switch off after logo display

              so led strips has to be changed ? or maybe led driver don't give the right voltage ?

              Comment


                #8
                Re: Polaroid TV switch off after logo display

                With an LED tester you can find out which strip is not good. Or put the meter on the connector and turn on the TV. The maximum value read is the closest to the truth. Otherwise the protection enters immediately, the voltage decreases and the read value is erroneous.
                If the baclight appears and then turns off and the TV restarts, it may be a software problem.
                Also check if the BL-ON command (for backlight lighting) remains permanent. If so and the LEDs go out, it's the backlight problem. If not, it is the software problem or the motherboard.
                Last edited by yokoono; 08-16-2020, 08:22 AM.

                Comment


                  #9
                  Re: Polaroid TV switch off after logo display

                  i tested the voltage with led backlight tester and it gives 49.8v for each connector , i don't know what is the expected voltage i should have ?
                  Attached Files

                  Comment


                    #10
                    Re: Polaroid TV switch off after logo display

                    The LED tester is a constant current generator. With it you can light LED bars if they are good. If it is ok, the lights come on.
                    https://www.youtube.com/watch?v=4DS8_utsLPo

                    Comment


                      #11
                      Re: Polaroid TV switch off after logo display

                      i don't know why but i didnn't change anything just doing some tests and now the tv turns on normally , and i have now the voltages of the back light at 54v and it was before at 49.8v (when conncted with led tester) ... strange !!! maybe something is at the end of his life either backleds or on the boost circuit of the led-driver ? ... what do you think ...

                      Comment


                        #12
                        Re: Polaroid TV switch off after logo display

                        1. imperfect contact to the sockets
                        2. imperfect contact to an LED
                        3. LEDs with higher current
                        4. problems with the LED converter
                        If the TV is more than 3 years old and you want to keep it, it is worth replacing the LED strips with new ones.
                        Last edited by yokoono; 08-28-2020, 09:33 AM.

                        Comment


                          #13
                          Re: Polaroid TV switch off after logo display

                          Turn down the backligts level to as low as possible so if you have bad LED's then you may be able to use it a little bit longer before it goes bad completely.
                          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: Polaroid TV switch off after logo display

                            yes thank you for your help, i will use the TV and see how much time it remains alive and let you know ... ( maybe with the led tester the high voltage shorted the bad leds and now i have more led working but maybe not for a long time ...will see)

                            thank you again for your help .

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