sharp lc-40sh340k Baclight Ptoblem.

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  • Mikeyboy2007
    Badcaps Veteran
    • Mar 2013
    • 745
    • Scotland
    #1

    sharp lc-40sh340k Baclight Ptoblem.

    hi guys i have had this sharp lc-40sh340k laying around for a while now. when you switch it on it goes on displays picture and light on screen but after 2 seconds the backlights switch off. i have tried different PSUs and same issue, also purchased a used inverter board on ebay for this tv and same issue. could it be the mainboard or even possible one of the CCFL tubes itself possibly breaking the circuit and shutting down the inverter ?

    any help would be great thanks
    Tags: None
    • nomoresonys
      Badcaps Legend
      • Jan 2013
      • 12079
      • U.S.
      #2
      Re: sharp lc-40sh340k Baclight Ptoblem.

      did you check all the fuses?

        Comment

        • nomoresonys
          Badcaps Legend
          • Jan 2013
          • 12079
          • U.S.
          #3
          Re: sharp lc-40sh340k Baclight Ptoblem.

          2 seconds to black seems like a capacitor issue?

            Comment

            • Mikeyboy2007
              Badcaps Veteran
              • Mar 2013
              • 745
              • Scotland
              #4
              Re: sharp lc-40sh340k Baclight Ptoblem.

              nomoresonys i already replaced psu with a known working one and what fuses will i check ? would it be a fuse though if the backlight is going on for even 2 seconds ?

                Comment

                • nomoresonys
                  Badcaps Legend
                  • Jan 2013
                  • 12079
                  • U.S.
                  #5
                  Re: sharp lc-40sh340k Baclight Ptoblem.

                  post some good clear pics., of all the boards and one of the whole back and how theyre connected, a pic. is worth a thousand words.

                    Comment

                    • nomoresonys
                      Badcaps Legend
                      • Jan 2013
                      • 12079
                      • U.S.
                      #6
                      Re: sharp lc-40sh340k Baclight Ptoblem.

                      you might have gotten a bad inverter from ebay, it may be a lamp issue.

                        Comment

                        • nomoresonys
                          Badcaps Legend
                          • Jan 2013
                          • 12079
                          • U.S.
                          #7
                          Re: sharp lc-40sh340k Baclight Ptoblem.

                          did you grab a service manual?

                            Comment

                            • nomoresonys
                              Badcaps Legend
                              • Jan 2013
                              • 12079
                              • U.S.
                              #8
                              Re: sharp lc-40sh340k Baclight Ptoblem.

                              http://www.toms-service-manuals.com/...h=Submit+Query this should help, pretty good info on troubleshooting.
                              Last edited by nomoresonys; 12-28-2014, 01:27 PM.

                                Comment

                                • Mikeyboy2007
                                  Badcaps Veteran
                                  • Mar 2013
                                  • 745
                                  • Scotland
                                  #9
                                  Re: sharp lc-40sh340k Baclight Ptoblem.

                                  are these any helpfull ? and not sure what im looking for in the service manual ?
                                  Attached Files

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA
                                      #10
                                      Re: sharp lc-40sh340k Baclight Ptoblem.

                                      It will only take one bad lamp to cause the inverter to shutdown.
                                      You can first verify that the 24VDC is still present on the inverter board and also the bl_on is also present.
                                      Some time you can bypass the detection time out on the PWM IC of the inverter circuit but you will need to get the spec of the IC.
                                      You may have to take the panel apart to inspect the lamp but it is delicate works.
                                      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

                                        • Mikeyboy2007
                                          Badcaps Veteran
                                          • Mar 2013
                                          • 745
                                          • Scotland
                                          #11
                                          Re: sharp lc-40sh340k Baclight Ptoblem.

                                          ive taken a few samsung panels apart to change CCFL tubes. i will check 24v and BL_ON and get back to you thanks

                                            Comment

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