HP-L1506 keeps blowing internal fuse

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  • Agent24
    I see dead caps
    • Oct 2007
    • 4924
    • New Zealand

    #21
    Re: HP-L1506 keeps blowing internal fuse

    Originally posted by techfixit
    The third monitor is turning on but then immediately switches off and restarts as soon as the test image appears. I've got 318v at the main filter cap and i've checked all the other filter caps with an ESR meter and all of those tested good.
    Did you check the SMPS controller's Vcc supply filtering capacitor? If that is bad you may get those symptoms.
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #22
      Re: HP-L1506 keeps blowing internal fuse

      Originally posted by techfixit
      Some good news to report. I changed the failed Mosfets on all 3 boards and 2 of the monitors are working perfectly now

      The third monitor is turning on but then immediately switches off and restarts as soon as the test image appears. I've got 318v at the main filter cap and i've checked all the other filter caps with an ESR meter and all of those tested good.

      Has anyone got any suggestions?
      So you see the screen lights up for second and then the power LED goes off?
      Did you check the transistors for the inverter circuit Q714, 715?
      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

      • techfixit
        Member
        • Feb 2014
        • 44
        • Ireland

        #23
        Re: HP-L1506 keeps blowing internal fuse

        Originally posted by Agent24
        Did you check the SMPS controller's Vcc supply filtering capacitor? If that is bad you may get those symptoms.
        Excuse my ignorance but what capacitor would that be? Can you highlight it on one of my photos?

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #24
          Re: HP-L1506 keeps blowing internal fuse

          Originally posted by techfixit
          Excuse my ignorance but what capacitor would that be? Can you highlight it on one of my photos?
          Two small lytics caps in the primary side next to small 4-pin Opto isolator and ref diode IC702.
          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

          • techfixit
            Member
            • Feb 2014
            • 44
            • Ireland

            #25
            Re: HP-L1506 keeps blowing internal fuse

            Originally posted by budm
            So you see the screen lights up for second and then the power LED goes off?
            Did you check the transistors for the inverter circuit Q714, 715?
            I get picture (test image) for about a second then the display shuts down, The status light also changes from green to orange just as the screen powers off. It continues this cycle until i press the on/off button or unplug the power cable. I've tried unplugging all connections attached to the power supply board but it still does the same thing.

            Both transistors are C5707. Testing them in circuit i get:
            Black-B + Red-C=410, Red-E=210
            Red-B + Black-C=410, Black-E=210

            Is that a good transistor or should i remove and test out of circuit?
            Last edited by techfixit; 02-27-2015, 07:55 PM.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #26
              Re: HP-L1506 keeps blowing internal fuse

              "Black-B + Red-I=410, Red-E=210
              Red-B + Black-I=410, Black-E=210"
              I do not understand what the readings are, the transistor has EMITTER, COLLECTOR, and BASE.
              Also 410 Ohms, K Ohms, or M Ohms, same for the 210.
              http://s807.photobucket.com/user/bud...tml?sort=3&o=2
              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

              • techfixit
                Member
                • Feb 2014
                • 44
                • Ireland

                #27
                Re: HP-L1506 keeps blowing internal fuse

                Sorry that was a typo "I" should have been "E" for emitter. The first test was done in diode mode so i presume the figure is voltage drop?

                Black-B + Red-C=410, Red-E=210
                Red-B + Black-C=410, Black-E=210

                Here's what i get testing the resistance

                Black-B + Red-C= .468k, Red-E= 3.08k
                Red-B + Black-C=.468k Black-E= .148k max initially then slowly decreases

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #28
                  Re: HP-L1506 keeps blowing internal fuse

                  "Red-B + Black-C=.468k Black-E= .148k" 148 Ohms that does not look right. Since you have the other board you can do comparison reading or take it out and test again off the board. I use Ohm mode to check for resistance reading since bad semiconductor will not act like diode any more (conducts in both direction).
                  You can also take those two transistors and see if it will still go into shutdown, you just will not have backlights.
                  Last edited by budm; 02-27-2015, 08:12 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

                  • stj
                    Great Sage 齊天大聖
                    • Dec 2009
                    • 30944
                    • Albion

                    #29
                    Re: HP-L1506 keeps blowing internal fuse

                    test off the board.

                    Comment

                    • techfixit
                      Member
                      • Feb 2014
                      • 44
                      • Ireland

                      #30
                      Re: HP-L1506 keeps blowing internal fuse

                      Cheers guys, Will do as instructed and report back with the results It'll have to wait until tomorrow unfortunately as it's 2:40am here.... ZZZZZZZZZZZZzzzzzzzzzzzzzzzz

                      Comment

                      • techfixit
                        Member
                        • Feb 2014
                        • 44
                        • Ireland

                        #31
                        Re: HP-L1506 keeps blowing internal fuse

                        Ok so i tested both transistors out of circuit and compared them to a pair from a working board and the results are identical so i guess there working fine.

                        Comment

                        • Agent24
                          I see dead caps
                          • Oct 2007
                          • 4924
                          • New Zealand

                          #32
                          Re: HP-L1506 keeps blowing internal fuse

                          You could swap them with the good pair to be sure.

                          It happens rarely, but sometimes a part can test OK, but be just bad enough to fail under operation.
                          "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                          -David VanHorn

                          Comment

                          • techfixit
                            Member
                            • Feb 2014
                            • 44
                            • Ireland

                            #33
                            Re: HP-L1506 keeps blowing internal fuse

                            Originally posted by Agent24
                            You could swap them with the good pair to be sure.

                            It happens rarely, but sometimes a part can test OK, but be just bad enough to fail under operation.
                            I just tried the pair from the fully working board in the non working board and got the same result as before.. will power on for a second or 2 then restart

                            Comment

                            • Agent24
                              I see dead caps
                              • Oct 2007
                              • 4924
                              • New Zealand

                              #34
                              Re: HP-L1506 keeps blowing internal fuse

                              Did you check\swap the big grey capacitor between the 2SC5707s?

                              Have you checked the inverter transformers winding resistance, compared to each other and to one of the working boards?

                              Have you tried swapping the SMPS controller IC601 with one from a working board?
                              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                              -David VanHorn

                              Comment

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