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Sharp LC-26DV24U has intermittent white screen

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    Sharp LC-26DV24U has intermittent white screen

    Hey guys, I have been lurking your forums for a while now but I'm kind of shy about posting. I have had marginal success repairing lcd displays and tv's. Usually I find bad caps or transformers, using existing forums as a guide. I have the common hand tools, a soldering iron, a digital multimeter that can test capacitance, though not an ESR. I really enjoy repairing things and you guys do great work.

    I tend to find tv's in the electronics bin at the local dumps. They don't like that I take them so I try to get them on the sly. I do not resale the tv's and displays as I'm not confident enough in my repair work to know that I'm not selling someone a POS that will die in a month. The tv's and displays I have repaired are being put to good use in my home and have been working for nearly a year though. I do have a few projects that I was hoping to get into with you guys, one is a 42" vizio that would be a huge upgrade for the living room. Another is a 32" emerson that would replace my son's 19" dynex.

    My question for today though involves the sharp LC-26DV24U. When I rescued it from the dump I found it had a good picture, but no sound. No big deal, I'll use it for a display and replace the two 19" one's I currently use. I used it for about a week and suddenly while working on homework the screen went completely white. I searched the forums, did some testing, downloaded the service manual, but I haven't gotten anywhere. So while I was troubleshooting I noticed I only have 110v line voltage at the receptacle. I left it on for a while and the display came back. I got my meter out again and noticed the line voltage had climbed to 115v. It seemed fine for a few hours then it went white screen again, the line voltage was 119v this time. I tried kicking it with the cover both on and off but no avail. J/K

    So I'm wondering if any one has had experience with displays that are particularly sensitive to voltage fluctuations. I couldn't find a spec sheet that tells what % above and below 120v is acceptable. All the nameplate says is 120v~. Is this observation totally irrelevant or are there parts I should be able to pinpoint based on this observation?

    Even if I do get the display working I would need to troubleshoot the sound as well :\ To be honest, I would rather work on the vizio first, but I thought this was interesting and worth asking you guys.

    Thanks for all you do.
    Boonami

    #2
    Re: Sharp LC-26DV24U has intermittent white screen

    110V is absolutely fine for a 120V device, you are probably looking at a non-power-supply related fault.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment


      #3
      Re: Sharp LC-26DV24U has intermittent white screen

      Thanks tom for the speedy response. The display came back and I tested line side again. This time it was 120v, killing my hypothesis. At which point I began looking for a way to delete my post so I don't look like such a noob. Any ways now that I have made a post I won't feel so awkward when I post on the SV420XVT1A.
      Thanks again.

      Comment


        #4
        FIXED - Sharp TV - Intermittent White Screen - Bad Q419

        I have the same model Sharp TV with the same symptoms. The TV would sometimes work perfectly, then go to white screen (audio OK) and sometimes back to working perfectly again.

        I saw Posts saying to check F404 and Q413 - My fuse F404 was not blown, and replacing the Q413 transistor did not fix it.

        On Q413 I had about 12.4 VDC on the Emitter, 12.3 VDC on the Base and about 1.5 VDC on the Collector. My service manual called for 11.6 VDC on the Base lead. As a Test, I used a 150 Ohm resistor from Q413 Base to metal chassis ground, and that made the TV work OK.

        I replaced the Q419 NPN silicon driver transistor, and now the TV has been restored to 100% proper operation.

        I hope that helps someone else down the line - bigkitty

        Comment


          #5
          Re: Sharp LC-26DV24U has intermittent white screen

          Hi,

          Thank you so much for sharing what you found!

          I have the same tv and I would like to fix it for my mother-in-law...

          Where did you buy Q419 (Part# KRC102SRTK) and is there an NTE, ECG or other substitute that will work?

          Thank you again,

          Robert

          Comment


            #6
            Re: Sharp LC-26DV24U has intermittent white screen

            REPLACED Q419 (NTE2414) & Q413 (2SA1020) ALONG WITH R418 100 ohm

            Comment


              #7
              Re: Sharp LC-26DV24U has intermittent white screen

              @emosdad23004, but did you check the Collector and the Base voltages of Q413?
              Service manual. Q413, Q419 tested OK?
              http://elektrotanya.com/?q=showresul...oria=&kat2=all
              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

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