Sharp LC-37SB24U two seconds to black

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  • tsm174
    Member
    • Apr 2015
    • 23
    • USA

    #1

    Sharp LC-37SB24U two seconds to black

    I'm working on this tv which will turn on briefly, then go black. Symptoms are almost identical to what someone else posted about a few years ago here: (https://www.badcaps.net/forum/showthread.php?t=17101).

    When I turn the tv on the picture comes up with audio for about 2 seconds the picture then goes out. I can still see the picture with a flashlight and hear the audio.

    From some other reading I suspect either the inverter board or maybe the a bad lamp but I'm unsure how to proceed.

    (I do have another picture of the board with all the video/audio inputs on it but it's on my phone which is dead at the moment)
    Attached Files
  • tsm174
    Member
    • Apr 2015
    • 23
    • USA

    #2
    Re: Sharp LC-37SB24U two seconds to black

    Anyone know how I can determine if the inverter is bad or if it's a bad lamp?

    Comment

    • hazi12
      New Member
      • Jun 2015
      • 8
      • Czech Republic

      #3
      Re: Sharp LC-37SB24U two seconds to black

      Measure the resistance to the inverter transformers, it must all be the same.

      Comment

      • tsm174
        Member
        • Apr 2015
        • 23
        • USA

        #4
        Re: Sharp LC-37SB24U two seconds to black

        The inverter transformer is the one with two wire windings, right? (6 of them on my board). Where do I measure across - where do I start? And as far as measuring to the transformer, which pin? There 10 pins on each.

        Comment

        • ammarben
          Senior Member
          • May 2013
          • 63
          • algeria

          #5
          Re: Sharp LC-37SB24U two seconds to black

          The inverter transformer T7501;T7502...mesure the secondary winding
          they must all be the same

          Comment

          • tsm174
            Member
            • Apr 2015
            • 23
            • USA

            #6
            Re: Sharp LC-37SB24U two seconds to black

            Thanks. Is the secondary winding the one with 8 fins, not four? There are four pins on that half of the transformer. I tried to measure resistance across all combinations of the pins on a couple of them and get an open circuit so I guess I'm not measuring the right things. I'll see if I can find a pin diagram for the transformer.
            Last edited by tsm174; 06-14-2015, 10:32 AM.

            Comment

            • ammarben
              Senior Member
              • May 2013
              • 63
              • algeria

              #7
              Re: Sharp LC-37SB24U two seconds to black

              are you using the ohmetre to test the transformer?

              Comment

              • tsm174
                Member
                • Apr 2015
                • 23
                • USA

                #8
                Re: Sharp LC-37SB24U two seconds to black

                yes. I can measure some resistance across the primary windings, but I don't get any resistance on the secondary windings (or what I think are the secondary windings).
                Last edited by tsm174; 06-14-2015, 10:39 AM.

                Comment

                • ammarben
                  Senior Member
                  • May 2013
                  • 63
                  • algeria

                  #9
                  Re: Sharp LC-37SB24U two seconds to black

                  https://www.youtube.com/watch?v=b36w2GNrH6Y

                  http://preher-tech.com/documents/tes...ormersinlcdtvs
                  Last edited by ammarben; 06-14-2015, 10:42 AM.

                  Comment

                  • tsm174
                    Member
                    • Apr 2015
                    • 23
                    • USA

                    #10
                    Re: Sharp LC-37SB24U two seconds to black

                    Thanks, I'll check those out a little later on.

                    Comment

                    • tsm174
                      Member
                      • Apr 2015
                      • 23
                      • USA

                      #11
                      Re: Sharp LC-37SB24U two seconds to black

                      Ok, finally got around to checking these. Secondary windings (two per transformer) all measure around 550 ohms. Didn't find any blown resistors on the inverter board either.

                      Comment

                      • tsm174
                        Member
                        • Apr 2015
                        • 23
                        • USA

                        #12
                        Re: Sharp LC-37SB24U two seconds to black

                        After re-installing the inverter board and doing one final reset (plugging in TV with vol + chan - pressed), it seems to be working all well again!

                        It's nice to have it working again, but a little frustrating to not really know what the problem was to begin with.

                        Comment

                        • tsm174
                          Member
                          • Apr 2015
                          • 23
                          • USA

                          #13
                          Re: Sharp LC-37SB24U two seconds to black

                          resurrecting my old thread - the tv went back to it's old behavior again. 2 seconds to black.

                          Based on other posts I was able to jump C7558 to fire up the tv, reset the lamp error and monitor errors, and the TV looks good.

                          I was able to verify with the test patterns in the service menu that all the bulbs are firing (as far as I can tell - the whole screen looked bright white.)

                          BUT, I read that leaving c7558 jumped is a fire hazard, which I don't want to leave. Is there a way to further diagnose what the issue might be?

                          Comment

                          • tsm174
                            Member
                            • Apr 2015
                            • 23
                            • USA

                            #14
                            Re: Sharp LC-37SB24U two seconds to black

                            At this point I'm more or less ready to throw in the towel, so I opened up the panel to inspect for bad bulbs. Again, while I think they are all lighting, I did find one that has some black at the end of the tube. Maybe this one is failing?
                            Attached Files

                            Comment

                            • budwich
                              Badcaps Legend
                              • Jul 2015
                              • 3097
                              • Canada

                              #15
                              Re: Sharp LC-37SB24U two seconds to black

                              I would say that bulb is your likely issue. Its probably failing to start some times, increment a counter which eventually causes your set to turn down and not run any more.

                              Comment

                              • Nick's Tvs
                                Badcaps Veteran
                                • Jan 2014
                                • 621
                                • USA

                                #16
                                Re: Sharp LC-37SB24U two seconds to black

                                My set has its top CCFL that won't light up. I swapped it with the one right below it and tried again to make sure the issue was with the specific light, and it is.
                                I have another 37" Sharp in the shop but it uses different ccfls that are ever so slightly longer and won't fit properly. Where can I buy a replacement light for it?
                                I also have a samsung LCD 40" that was dropped and somehow everything remained intact except one of the ccfls broke and I need one for that model as well. Where can I buy these?? Also how do I figure out the specs on these? Never had to replace a CCFL before.

                                http://www.ccflwarehouse.com/30x83fuspcc.html

                                Would this work for this set??
                                Last edited by Nick's Tvs; 03-05-2016, 11:47 AM.

                                Comment

                                • Rider
                                  New Member
                                  • Oct 2014
                                  • 8
                                  • Canada

                                  #17
                                  Re: Sharp LC-37SB24U two seconds to black

                                  ccflwarehouse biggest rip-off U'll ever see!
                                  I just repaired a 19" Samsung TV/Monitor that needed 1 ccfl
                                  The set uses 2 of them so decide while I was in there would change both
                                  ccfl warehouse wanted $9.95 US a piece + $17.95 shipping and a 2 week wait!
                                  they were 481mmX2.4mm your standard 19 inch monitor size
                                  So here's what I did go to Aliexpress (China's Amazon)
                                  Type in the size I was looking for...
                                  And sure enough found a lot of 10 for $10 US and FREE shipping
                                  toke 3 weeks but was not in a rush!
                                  TV works again total cost of repair $2 bucks!

                                  Comment

                                  • michael dranfield
                                    Badcaps Veteran
                                    • Jan 2016
                                    • 232
                                    • England

                                    #18
                                    Re: Sharp LC-37SB24U two seconds to black

                                    Originally posted by tsm174
                                    At this point I'm more or less ready to throw in the towel, so I opened up the panel to inspect for bad bulbs. Again, while I think they are all lighting, I did find one that has some black at the end of the tube. Maybe this one is failing?
                                    Its a common problem with sharp sets and is usually caused by the white plastic holder the lamp is clipped into making a bad connection to the CCFL.

                                    Comment

                                    • michael dranfield
                                      Badcaps Veteran
                                      • Jan 2016
                                      • 232
                                      • England

                                      #19
                                      Re: Sharp LC-37SB24U two seconds to black

                                      Have a look at this guys.
                                      Attached Files

                                      Comment

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