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Broken LCD HDTV

Discussion in 'Electrical Engineering' started by [email protected], May 28, 2008.

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  1. Guest

    My 5 months old LCD HDTV (a 19" Philips model with 1440x900 16:10 resolution
    and PC input, mostly used for computer stuff) broke down yesterday. It is
    not completely dead. It dies within about 10 to 20 minutes of being powered
    on. By "dies" it no longer functions and the screen goes dark but the back
    light illumination appears to still be on. It won't turn off by remote or
    the buttons located on the top edge. I have to unplug the AC power.

    I believe the problem is a thermal condition likely in the PSU.

    This all started when I started watching WTOV-DT channel 9.3 weather radar.
    Someone online mentioned they saw the new channel so I checked it out. As
    some storms happened to be coming by the past few days, I left the TV on
    all night a couple times. Normally I have left it on with the PC, which
    would go into video power saver made shutting off most display functions.
    But with the radar it remained running constantly. I neglected to think
    about it. I was more concerned about the speed of getting it turned on if
    I wanted to watch in the middle of the night as that takes almost a minute
    for it to "boot up" from cold-off.

    I did notice once that the air rising from the top side vents was particularly
    hot. I shut it off at that time. But later when I had it back on again, it
    eventually just up and died on its own, like the CPU had frozen.

    I have allowed it to spend much time cooling down (hours in a cool room) and
    tried it again. The longest it will now run is about 20 minutes. When it
    actually dies (I finally watched it for long enough to see it do this) it
    does some kind of pixelation thing that is rather different than digital TV
    pixelation. It does this even for analog TV channels and PC input. It then
    blanks out and resets a couple times, coming back on. Finally it stays off.

    It's unplugged for now and I won't use it in case such usage could cause more
    permanent damage.

    I'm contemplating opening it up and trying to see if I can figure out what
    might be wrong inside. Maybe it has gotten too dusty inside and is not
    letting heat out fast enough and its a simple thermal trip. That pixelation
    on the screen does seem to me that the CPU or other digital circuitry is
    getting a low or incomplete voltage situation.

    I've never opened up an LCD flat screen TV before. Are there any general
    suggestions on how to handle doing this to avoid damaging it in other ways?

    Has anyone here ever opened up one of these before?

    I'll only do this if I find it's not under warranty. I don't normally buy
    those extended warranty plans for something in this price range, and this
    event won't change that (I would for something in the $2000 price range).
    But maybe the factory warranty still covers it. I'll have to dig the box
    with all its paperwork out of the garage to see. Most things I buy don't
    break for years. This is the first thing to die that soon in at about 10
    years (a 5GB HD died a month after I bought it long long ago).
     
  2. Palindrome

    Palindrome Guest

    If it is only 5 months old, surely it is still very much under warranty?
    In the UK it would have 1 year's warranty as a minimum, from the
    supplier. Plus any additional warranty that the manufacturer might have
    provided.

    It sounds like permanent thermal damage.

    It may be that some thermal bonding material has become degraded and
    could be simply replaced - but that it a long shot.

    You could opening it up and seeing if blowing in large quantities of
    cold air made a difference. Then localising the air flow to pin down
    which area, and finally which component, is causing the problem. It may
    be that a better heatsink, possibly with a fan, may do the job, even if
    the component itself is now less thermally efficient than it once was..
     
  3. Dean Hoffman

    Dean Hoffman Guest

    Cut rest.

    This doesn't answer your question but there might be some guidance
    here: http://tinyurl.com/yuj27l
    Some hard core electronics users are here. It doesn't sound like any
    are EEs or fixers but maybe there is help there anyhow. There is a
    search feature near the top.

    Dean
     
  4. Guest

    | If it is only 5 months old, surely it is still very much under warranty?
    | In the UK it would have 1 year's warranty as a minimum, from the
    | supplier. Plus any additional warranty that the manufacturer might have
    | provided.
    |
    | It sounds like permanent thermal damage.
    |
    | It may be that some thermal bonding material has become degraded and
    | could be simply replaced - but that it a long shot.
    |
    | You could opening it up and seeing if blowing in large quantities of
    | cold air made a difference. Then localising the air flow to pin down
    | which area, and finally which component, is causing the problem. It may
    | be that a better heatsink, possibly with a fan, may do the job, even if
    | the component itself is now less thermally efficient than it once was..

    It does appear to have a 1 year warranty. Now I need to find my receipt
    to prove purchase date. I have receipt piles in several places.
     
  5. James Sweet

    James Sweet Guest


    If you can't warranty exchange, try posting on sci.electronics.repair,
    that's where the techs hang out. I would get out the freeze spray and a
    hair dryer and start poking around. Wouldn't hurt to check all the power
    supply rails before and after the fault condition as well. I've run into
    cases where a bad optocoupler would allow the voltage to slowly rise as
    the device warmed up, took forever to track down because the symptoms
    pointed to something else.
     
  6. Stephen B.

    Stephen B. Guest

    If you don't find the recipt check for the date code. Chances are it
    was MADE less than a year ago.
     
  7. Guest

    | |>
    |> | If it is only 5 months old, surely it is still very much under
    |> warranty?
    |> | In the UK it would have 1 year's warranty as a minimum, from the
    |> | supplier. Plus any additional warranty that the manufacturer might
    |> have
    |> | provided.
    |> |
    |> | It sounds like permanent thermal damage.
    |> |
    |> | It may be that some thermal bonding material has become degraded
    |> and
    |> | could be simply replaced - but that it a long shot.
    |> |
    |> | You could opening it up and seeing if blowing in large quantities
    |> of
    |> | cold air made a difference. Then localising the air flow to pin
    |> down
    |> | which area, and finally which component, is causing the problem.
    |> It may
    |> | be that a better heatsink, possibly with a fan, may do the job,
    |> even if
    |> | the component itself is now less thermally efficient than it once
    |> was..
    |>
    |> It does appear to have a 1 year warranty. Now I need to find my
    |> receipt
    |> to prove purchase date. I have receipt piles in several places.
    |>
    |
    | If you don't find the recipt check for the date code. Chances are it
    | was MADE less than a year ago.

    Good point! I'll check for that.
     
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