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Intermittent black screen on Sharp mod: LC-52D65U

Discussion in 'Repairing Electronics' started by Nickm52, Jul 3, 2017.

  1. Nickm52

    Nickm52 New Member

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    Hello everybody,

    I am new to the blog, so if I do not conform to the requests, please excuse me..

    My problem is intermittent on Sharp mod: LC-52D65U. The TV will work OK for a period of time (different), than the screen go black, with sound. When you turn the TV OFF and ON, it comes back OK again, than after some time the screen goes black and so on and so on...



    The unit is not so “young” and I can't get any information (service manual, trouble shooting, etc.). This is what I observed:

    On the inverter board DAC-60T012 Master (see picture), the nine (9) pin connector has the following voltage, when I HAVE and do NOT HAVE picture:


    upload_2017-7-3_15-32-38.png




    Picture: Pin Voltage No Picture: Pin Voltage
    2 3.3V 2 3.3V
    5 3.0V 5 0.0V
    8 2.84V 8 2.84V


    Pin 5 has an “ERR” designation.



    The second connector (three pin, not in the picture) coming from the power supply board has the following stable voltages in both “Picture” and “No Picture” states: pin 1: 60.7V; pin 2: Ground; Pin 3: 11.94V, all stable.



    The unit is not so “young” and It seems, I can't find any service/trouble shooting manuals/schematics...



    Any help is appreciated.

    Thanks Nick
     
  2. ramondo

    ramondo New Member

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  3. ramondo

    ramondo New Member

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  4. dave

    Dave New Member

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  5. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I would suspect it might well be a faulty CCFL tube (or more than one) - it's normal for the set to shut the inverter down completely if it detects a faulty tube.

    With some Sharp models you could get replacement tubes, and it wasn't 'too hard' a job changing them - but the difficulty is finding which tube (or tubes) it might be - and you should always change them in pairs anyway.

    Replacing all the tubes isn't cost effective, and as all the tubes are the same age I suspect that's really what you have to do - or they just come back a few weeks later with the same symptoms (with a different failed tube).
     
  6. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    In my experience the most common failure of these sorts of TVs is the inverter transformer itself. I had a TV with a nearly identical problem and it was fixed by replacing the $6 transformer. They fail much more easily than the tubes do.
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Only on the cheap junk makes, and while Sharp isn't a 'great' make they haven't commonly had transformer failures in the UK.
     
  8. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Is Samsung considered a cheap junk make?

    Either way I would try replacing the transformer before I try replacing the tubes. Much cheaper and much less effort.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It's a 'middling' make, but they have a habit of fitting sub-standard transformers and electrolytics - so on the 'transformers failing' front, they are a junk make.

    Assuming you can even get a transformer?, and bearing in mind there will be multiple ones on a screen of that size (only 'portables' have a single transformer).

    Interestingly Sony transformers never fail, with one exception - they bought a range of portable sets in from Beko (19 and 22 inch) while they were waiting for their own new range to come out, and they fail with great regularity. Now of course Sony don't even make such small sets, their smallest is 32 inch.
     
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