Philips 47PFH4109 blinking 2 times when powering

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  • Protker
    Member
    • Jan 2020
    • 10
    • Serbia

    #1

    Philips 47PFH4109 blinking 2 times when powering

    Hello!
    So i have a Philips 47PFH4109, and when i powering on the tv just blinks once, then after a 2 seconds blinks again, and does not turning on.
    I mean i measuring voltages such like 30V on the leds and the 12 volts on the other panels, which seems to be okay.
    I checked the backlight no issues with the leds.
    I checked every component such as all the mosfets, all the diodes, i dont see any bad capacitors (unfortunatelly i only can measure up to 200uF).
    I even took out the LD7591 chip and without it doing the same as before.
    Im just seeking for advice, or even someone enountered a similar problem?

    Im attaching some pictures if thats help.

    Thanks in advance!
    Attached Files
  • dskall
    Badcaps Legend
    • Oct 2016
    • 2905
    • usa

    #2
    Re: Philips 47PFH4109 blinking 2 times when powering

    You are getting voltages on your mainboard?
    I assume no responsibility for any stupid suggestions I might post.

    Comment

    • Protker
      Member
      • Jan 2020
      • 10
      • Serbia

      #3
      Re: Philips 47PFH4109 blinking 2 times when powering

      Yes i get voltages on the mainboard. Well on the power supply board is written that there should be 12V, i get 11,3 11,7V, so i assume that is ok. After powering on i measuring voltages up to 50V on the led connector, then it falls back to steady 30V. After that no nothing stays in standby mode.
      I should check if i get picture when its in standy mode no?
      Thanks

      Comment

      • Protker
        Member
        • Jan 2020
        • 10
        • Serbia

        #4
        Re: Philips 47PFH4109 blinking 2 times when powering

        So there is screen, only the backlight is missing.
        I have to say i tried to light up the backlight applying dc on the led connectors and around 50V it lights up both led strip nicely. This is the reason im assuming the strips are good.
        Maybe the supply board sensing that too much current was drawn by the strips and shuts off the backlight?

        Comment

        • dskall
          Badcaps Legend
          • Oct 2016
          • 2905
          • usa

          #5
          Re: Philips 47PFH4109 blinking 2 times when powering

          So you have image. On power board do you have a BL_on? Should have voltage on that terminal. Probably bad LED.
          I assume no responsibility for any stupid suggestions I might post.

          Comment

          • R_J
            Badcaps Legend
            • Jun 2012
            • 9535
            • Canada

            #6
            Re: Philips 47PFH4109 blinking 2 times when powering

            You likely have a bad led in one of the strings, if the current draw for the string is wrong, the tv power supply will detect that and shut down. I suspect one led is shorted and supplying a voltage from a bench supply will not detect the bad led but light the others in the string.

            The LD7591 is for the pfc circuit not for the led's
            Last edited by R_J; 12-25-2021, 01:28 PM.

            Comment

            • Protker
              Member
              • Jan 2020
              • 10
              • Serbia

              #7
              Re: Philips 47PFH4109 blinking 2 times when powering

              Thank you for all the comments and suggestions, i will tear down the tv as soon as i will have time for that, and will give you a feedback. Thanks!

              Comment

              • Protker
                Member
                • Jan 2020
                • 10
                • Serbia

                #8
                Re: Philips 47PFH4109 blinking 2 times when powering

                So im back, i tested the leds, every led strip is lights up nicely. I assembled the tv back again. Im starting to suspect maybe a capacitor lost its capacitance, and causing the trouble here? Primarily the ones in nearest to the led connector?

                Comment

                • dskall
                  Badcaps Legend
                  • Oct 2016
                  • 2905
                  • usa

                  #9
                  Re: Philips 47PFH4109 blinking 2 times when powering

                  How did you test led's?
                  I assume no responsibility for any stupid suggestions I might post.

                  Comment

                  • Protker
                    Member
                    • Jan 2020
                    • 10
                    • Serbia

                    #10
                    Re: Philips 47PFH4109 blinking 2 times when powering

                    I disassemled the whole tv took out the screen and applied dc to the strips.
                    I will try tomorrow to test the capacitors.

                    Comment

                    • Protker
                      Member
                      • Jan 2020
                      • 10
                      • Serbia

                      #11
                      Re: Philips 47PFH4109 blinking 2 times when powering

                      So i tested out the capacitors, all showing the right parameters(what is written on the caps). I found the exact schematics on the net, and according to the schematics everythings is fine.
                      The problem is whenever i turn on the tv, it flashes 2 times(trying to light up the backlight), but unfortunatelly gives up and after these 2 try remains unlighted (i have screen logo etc btw).
                      Attached Files

                      Comment

                      • vinceroger69
                        Badcaps Legend
                        • Mar 2012
                        • 6714
                        • uk

                        #12
                        Re: Philips 47PFH4109 blinking 2 times when powering

                        Originally posted by Protker
                        I disassemled the whole tv took out the screen and applied dc to the strips.
                        I will try tomorrow to test the capacitors.
                        just a thought, although the led strips light up using dc volts one strip maybe using more amps which maybe putting the set into protection mode
                        the latest led testers show voltage and amps
                        https://www.ebay.co.uk/itm/273214652...3ABFBMxK_Yo8Bf

                        Comment

                        • dskall
                          Badcaps Legend
                          • Oct 2016
                          • 2905
                          • usa

                          #13
                          Re: Philips 47PFH4109 blinking 2 times when powering

                          Will led's come on with t-con disconnected?
                          I assume no responsibility for any stupid suggestions I might post.

                          Comment

                          • Protker
                            Member
                            • Jan 2020
                            • 10
                            • Serbia

                            #14
                            Re: Philips 47PFH4109 blinking 2 times when powering

                            Nope, with disconnected tcon remains the same.. I measuring the +30VDC before the step up converter, seems that maybe the converter chip doesnt doing its job properly (PF7903BS) Sadly i cannot find any kind of data of this chip, so i can temper maybe with the feedback leg or ovp leg, to make it work...

                            Comment

                            • Protker
                              Member
                              • Jan 2020
                              • 10
                              • Serbia

                              #15
                              Re: Philips 47PFH4109 blinking 2 times when powering

                              Hello guys again. I managed to solve the backlight issue with this tv.
                              So i managed to take out the mosfet (in the datasheet is Q8104) and i figured out even though it was not shorted, but i couldnt open the fet with multimeter.
                              So I searched for a replacement and i found a random fet which had the same pinout. And it worked, lighted up the strip nicely. After i made sure that the mosfet is the problem i searched for a better replacement bc the random i found had 5ohm rds on resistance.
                              So i placed an IRF 540 and stopped working..
                              Hm.. then i found out if i decrease the resistance of the R8117 resistor from 7,5k to lets say 5,6k, then i can trick the ovp/dim pin of the PF7903BS chip. And thats that.
                              Thanks for the help and the suggestions!
                              Attached Files

                              Comment

                              • dskall
                                Badcaps Legend
                                • Oct 2016
                                • 2905
                                • usa

                                #16
                                Re: Philips 47PFH4109 blinking 2 times when powering

                                Nice job.
                                I assume no responsibility for any stupid suggestions I might post.

                                Comment

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