Philips 37PF7321/98 cannot turn on

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  • john_doe
    Senior Member
    • Apr 2013
    • 192
    • Malaysia

    #141
    Re: Philips 37PF7321/98 cannot turn on

    Originally posted by john_doe
    What is happening???

    I jump a ground to Gate and now the Gate is 20v and Yellow S(source) is 5v.

    And the pin 3 of 1305 is 0v.

    When I power off and on the tv, the led light on the front panel is green and stay green. Before this, the led is green and after about 2 sec will turn red.
    Just to be sure, I have remove the ground to G. And the voltage of the Gate is still 20v and the Source is still 5v.

    How is this possible?

    Comment

    • john_doe
      Senior Member
      • Apr 2013
      • 192
      • Malaysia

      #142
      Re: Philips 37PF7321/98 cannot turn on

      Originally posted by john_doe
      Just to be sure, I have remove the ground to G. And the voltage of the Gate is still 20v and the Source is still 5v.

      How is this possible?
      Originally posted by john_doe
      What is happening???

      I jump a ground to Gate and now the Gate is 20v and Yellow S(source) is 5v.

      And the pin 3 of 1305 is 0v.

      When I power off and on the tv, the led light on the front panel is green and stay green. Before this, the led is green and after about 2 sec will turn red.
      This is driving me nuts!

      Now when I power up the tv, the front panel LED light is off. I press the power button and the LED turned green. The tv screen also lighted up! I swear I didn't do anything.

      Am I seeing things? I better go and sleep.

      Comment

      • selldoor
        Slow Learner
        • Dec 2010
        • 7870

        #143
        Re: Philips 37PF7321/98 cannot turn on

        Great stuff - hope it lasts - I dont know if its possible to unstick a stuck transistor- maybe?

        If it doesnt come on again try heating that section of the board with a hairdryer maybe
        getting some voltage through heated something up making it work.
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #144
          Re: Philips 37PF7321/98 cannot turn on

          Darn, 143 posts and the TV start functioning by itself.
          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

          • bammbammfran
            Badcaps Veteran
            • Apr 2014
            • 476
            • USA

            #145
            Re: Philips 37PF7321/98 cannot turn on

            looks like we found part of the issue
            now if you do that with the 3 pin wire connected to the power supply, the relay might just kick on

            Comment

            • bammbammfran
              Badcaps Veteran
              • Apr 2014
              • 476
              • USA

              #146
              Re: Philips 37PF7321/98 cannot turn on

              Originally posted by john_doe
              Just to be sure, I have remove the ground to G. And the voltage of the Gate is still 20v and the Source is still 5v.

              How is this possible?
              you charged the transistor and it activated . I THINK !

              Comment

              • bammbammfran
                Badcaps Veteran
                • Apr 2014
                • 476
                • USA

                #147
                Re: Philips 37PF7321/98 cannot turn on

                Originally posted by budm
                Darn, 143 posts and the TV start functioning by itself.
                IT IS SAYING, Stop poking me !!

                Comment

                • john_doe
                  Senior Member
                  • Apr 2013
                  • 192
                  • Malaysia

                  #148
                  Re: Philips 37PF7321/98 cannot turn on

                  Originally posted by selldoor
                  Great stuff - hope it lasts - I dont know if its possible to unstick a stuck transistor- maybe?

                  If it doesnt come on again try heating that section of the board with a hairdryer maybe
                  getting some voltage through heated something up making it work.
                  I just check with the 3 pin plug 1305 connected. The Gate is 20v and the Source is 5v. Pin 1 and 2 of 1305 are 5v. Pin 3 is 0v.

                  When I power up the TV, no front panel LED light. Press the power on button and the LED light turn green and stay green. Screen on TV also lighted up.

                  Comment

                  • stj
                    Great Sage 齊天大聖
                    • Dec 2009
                    • 30940
                    • Albion

                    #149
                    Re: Philips 37PF7321/98 cannot turn on

                    Originally posted by bammbammfran
                    you charged the transistor and it activated . I THINK !
                    more likely it has a slight leak and is feeding back into the gate./base

                    Comment

                    • john_doe
                      Senior Member
                      • Apr 2013
                      • 192
                      • Malaysia

                      #150
                      Re: Philips 37PF7321/98 cannot turn on

                      Now the TV screen is not lighted. Voltages at mosfet 7531 and 3 pin plug 1305 no change.

                      TV is unstable.

                      Comment

                      • bammbammfran
                        Badcaps Veteran
                        • Apr 2014
                        • 476
                        • USA

                        #151
                        Re: Philips 37PF7321/98 cannot turn on

                        so that 20-20 and 5 are still at the transistor even when you power it off with the power button ?
                        To me that 20volts does not sound right
                        Also do you hear the relay click off when powering it off ?

                        Comment

                        • john_doe
                          Senior Member
                          • Apr 2013
                          • 192
                          • Malaysia

                          #152
                          Re: Philips 37PF7321/98 cannot turn on

                          Originally posted by bammbammfran
                          so that 20-20 and 5 are still at the transistor even when you power it off with the power button ?
                          To me that 20volts does not sound right
                          Also do you hear the relay click off when powering it off ?
                          When I first turn on the main without pressing the power on button, there is 20v and 5v and Gate and Source respectively but no green LED light on front panel.

                          When I press the power on button, green LED turn on. 20v and 5v still on.

                          Did not hear the relay click when pressing the power on button on and off. Only hear relay click when turn off main power.

                          Comment

                          • bammbammfran
                            Badcaps Veteran
                            • Apr 2014
                            • 476
                            • USA

                            #153
                            Re: Philips 37PF7321/98 cannot turn on

                            unplug the 11 pin wire on the standby board, then remove the number 7 wire from the plug
                            (you have to slightly lift the clip on the side of the plug with a pointy object and pull the wire out)
                            then power up
                            now check the voltages on the board that we were checking at the transistor and 1305
                            and do a separate check on the wire and the pin that we just removed

                            Comment

                            • john_doe
                              Senior Member
                              • Apr 2013
                              • 192
                              • Malaysia

                              #154
                              Re: Philips 37PF7321/98 cannot turn on

                              Originally posted by bammbammfran
                              unplug the 11 pin wire on the standby board, then remove the number 7 wire from the plug
                              (you have to slightly lift the clip on the side of the plug with a pointy object and pull the wire out)
                              then power up
                              now check the voltages on the board that we were checking at the transistor and 1305
                              and do a separate check on the wire and the pin that we just removed
                              When pin 7 removed, 20v and 5v still there. 1305 Pin 1 and 2 are 5v. Pin 3 is 0v.

                              11 pin wire:
                              Pin 4 is 12v
                              Pin 5 is 5v
                              Pin 7 is 5v
                              Pin 9 is 12v
                              Others are 0v
                              Last edited by john_doe; 06-20-2014, 08:34 PM.

                              Comment

                              • john_doe
                                Senior Member
                                • Apr 2013
                                • 192
                                • Malaysia

                                #155
                                Re: Philips 37PF7321/98 cannot turn on

                                Even with main power off, the Gate of 7531 still has voltage, 14v and discharging slowly.

                                Comment

                                • bammbammfran
                                  Badcaps Veteran
                                  • Apr 2014
                                  • 476
                                  • USA

                                  #156
                                  Re: Philips 37PF7321/98 cannot turn on

                                  ok
                                  with all power off and with it sit to discharge a bit
                                  check resistance in both directions from the Drain (yellowD) to the Gate pin (Yellow G)
                                  if zero or close to it, the transistor went bad

                                  going to need to cut a trace to isolate the Gate pin on that mosfet
                                  use an exacto knife or the like and cut out the yellow section at the end of the pink arrow
                                  I am trying to see if the gate is causing the 20 volts or the board itself
                                  Picture attached if I remember this time
                                  Attached Files

                                  Comment

                                  • john_doe
                                    Senior Member
                                    • Apr 2013
                                    • 192
                                    • Malaysia

                                    #157
                                    Re: Philips 37PF7321/98 cannot turn on

                                    Originally posted by bammbammfran
                                    ok
                                    with all power off and with it sit to discharge a bit
                                    check resistance in both directions from the Drain (yellowD) to the Gate pin (Yellow G)
                                    if zero or close to it, the transistor went bad

                                    going to need to cut a trace to isolate the Gate pin on that mosfet
                                    use an exacto knife or the like and cut out the yellow section at the end of the pink arrow
                                    I am trying to see if the gate is causing the 20 volts or the board itself
                                    Picture attached if I remember this time
                                    Resistance from Drain to Gate is OL both direction.

                                    7531 is new. Is it really necessary to cut trace? I have never done this.

                                    Comment

                                    • bammbammfran
                                      Badcaps Veteran
                                      • Apr 2014
                                      • 476
                                      • USA

                                      #158
                                      Re: Philips 37PF7321/98 cannot turn on

                                      7531 is new ???
                                      when did this get changed ???

                                      yes, you have to cut it since there are no jumpers to remove.
                                      it's an easy redo

                                      Comment

                                      • john_doe
                                        Senior Member
                                        • Apr 2013
                                        • 192
                                        • Malaysia

                                        #159
                                        Re: Philips 37PF7321/98 cannot turn on

                                        Originally posted by bammbammfran
                                        7531 is new ???
                                        when did this get changed ???

                                        yes, you have to cut it since there are no jumpers to remove.
                                        it's an easy redo
                                        It was replaced yesterday before our test. I replaced it because I wanted to test it out of circuit and since it is out, I replaced a new one.

                                        Ok, trace is cut.

                                        Comment

                                        • bammbammfran
                                          Badcaps Veteran
                                          • Apr 2014
                                          • 476
                                          • USA

                                          #160
                                          Re: Philips 37PF7321/98 cannot turn on

                                          now recheck usual voltages at G D S and at 1305 and also check the pad to the right of the cut

                                          Comment

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