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    Toshiba 40ft1u blows fuse

    I have a Toshiba 40 FT1 U. It was hit with a power surge. And the fuse blew. When I install a new fuse and plug it in and it blows instantly. I can't find any shorts on the mosfet or Bridge rectifier Maybe someone can take a look at the power board And has an idea where to test for shorts.
    Attached Files

    #2
    Re: Toshiba 40ft1u blows fuse

    Do you have any shorts on the cold side?
    Did you have the main board plugged in at all?
    -Thomas
    I'm a hardware engineer focused on networking equipment for my day job. I void warranties and fix consumer electronics for fun.

    Comment


      #3
      Re: Toshiba 40ft1u blows fuse

      I have the other boards disconnected. Still blows up fuse instantly. So the short has to be on the coldside I'm not sure where to start testing and what the values or for things. The green disc beside the power connector Is that supposed to show closed Or have some resistance. ?

      Comment


        #4
        Re: Toshiba 40ft1u blows fuse

        Likely is a NTC thermistor. Should have a resistance. What’s the markings on it?

        For the cold side: there are two heat sinked three pinned parts (D201, D202). Any shorts across the combination of two pins for each part? Any shorted to ground? What’s the marking on them?
        Last edited by ngth82; 03-31-2020, 12:11 AM.
        -Thomas
        I'm a hardware engineer focused on networking equipment for my day job. I void warranties and fix consumer electronics for fun.

        Comment


          #5
          Re: Toshiba 40ft1u blows fuse

          1) What is the resistance of the main filter cap C101?
          2) What is the resistance between the ~ of the bridge rectifier?
          3) What is the resistance of VS101?
          Last edited by budm; 03-31-2020, 12:41 AM.
          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


            #6
            Re: Toshiba 40ft1u blows fuse

            Vs101 is 0 the rest ill check tomorrow

            Comment


              #7
              Re: Toshiba 40ft1u blows fuse

              For starters you should check what is circled with red.
              Since the source does not have a PFC, you can put a 220v / 100w bulb in the place of fuse. Try it without mainboard, backlight etc. If the light bulb is bright it is not ok.
              Attached Files
              Last edited by yokoono; 03-31-2020, 01:55 AM.

              Comment


                #8
                Re: Toshiba 40ft1u blows fuse

                Did you use the same type fuse? That is T 6.3A H/250V.

                Comment


                  #9
                  Re: Toshiba 40ft1u blows fuse

                  Originally posted by microvibe View Post
                  Vs101 is 0 the rest ill check tomorrow
                  But you indicate that he Bridge rectifier tested OK are you sure? If you check between ~ of the bridge rectifier you would have seen it shows as shorted since the VS101 is connected in parallel with the ~ pins of the rectifier.
                  More likely that the VS101 is shorted out, common failure for this power supply when power surge occurs, so lift one leg of VS101 off the board and check the resistance between ~ pins of the bridge to see if it shows 0 Ohm or not.
                  Last edited by budm; 03-31-2020, 02:22 AM.
                  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


                    #10
                    Re: Toshiba 40ft1u blows fuse

                    No short on the rectifier after I lift one leg. Vs101. J105 resistor show short or is it just very low resistance?

                    Comment


                      #11
                      Re: Toshiba 40ft1u blows fuse

                      If I connect a light bulb across the fuse. Can I test the TV with vs. 101 removed? Or does that littelfuse need to be there? I can't find anything matching on the boards I have here.

                      Comment


                        #12
                        Re: Toshiba 40ft1u blows fuse

                        The bulb should be mounted as protection, to protect the components. But for a short time. If it lights up, turn off the power immediately. It is used without the psu having a load. Start with the stb part. Switch off the power supply and see if you have STB voltage. The bulb should not light or just very briefly until the filter capacitor is charged.

                        Comment


                          #13
                          Re: Toshiba 40ft1u blows fuse

                          I found. A match for vs 101 I installed it. Put in a new fuse and the TV's working fine. Thanks for your guys's help. Much appreciated

                          Comment


                            #14
                            Re: Toshiba 40ft1u blows fuse

                            Thanks for the follow-up.
                            BTW, Jxxx: J = JUMPER
                            Last edited by budm; 03-31-2020, 03:50 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

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