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Fluorescent LCD backlight lamp life turnon-off lcd monitor screenblank/screensaver???

Discussion in 'Electronic Basics' started by mike, Apr 11, 2005.

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  1. mike

    mike Guest

    Just got a flat-panel LCD monitor.
    I'm wondering what I should do to maximize backlight life.
    The fluorescent backlight will wear out if I leave it running all the time.
    But it's my understanding that the worst/most stressful thing you can do
    to a fluorescent lamp it to turn it on.

    Is there a screen blank (lamp turnoff) strategy that makes significant
    life improvement over not worrying about it?

    Thanks, mike
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  2. PeteS

    PeteS Guest

    In that wonderful LCD monitor you got there is a backlight inverter
    (producing around 600 - 1500Vac). One of the pins very commonly found
    on it is 'Sleep' which is used for exactly what you would want to do.
    Without knowing what model it is and where it's connected, it's hard to
    comment further

    Cheers

    PeteS
     
  3. mike

    mike Guest

    The question is/was NOT HOW to turn it off.
    The question is/was, "does turning it on/off improve the overall tube life?"
    And What's the tradeoff between leaving it running vs turning it on/off
    a lot.
    There's gotta be a peak somewhere on that curve. It's probablly broad,
    but...
    mike

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  4. PeteS

    PeteS Guest

    Well, we do LCD displays (industrial types, but the same type of
    screen - TFT-LCD) and we put the backlight in sleep mode after a
    programmable time (usually 30 sec to 1 min) of no touch/mouse activity.

    We have a number of units that are still going strong after 3 years.

    For the best scoop, go check out the info on the webistes of the LCD
    manfacturers.

    Some names are Sharp, Kyocera and TDK (well, they are the ones I use)

    Cheers

    PeteS
     
  5. I see no reason why it would hurt the tube to turn it on and off.

    In fact most fluoroscent tubes are turned on and off 50/60 times
    a second, as they are driven by mains AC power.

    The mechanisms for aging in fluoroscent tubes are usually that the
    fosforent layer which transform the ultraviolet light into visible
    light is being used up. So it should be good for the lifetime to turn
    it off whenever it is not needed.

    The OP is maybe thinking about common incandescent light bulbs, which
    take a beating every time they are turned on and off. But fluoroscent
    tubes do not work like that.
     
  6. mike

    mike Guest

    I'm always skeptical when a sentence starts off, "I see no reason
    why..." Can you point me to some measurement data or vendor proclamations?
    That's different. The electrodes are hot and if there's mercury in
    there it's vaporized etc. Not the same as striking a cold tube.

    Maybe it doesn't matter...that's what I'm asking.
    Interesting. I've NEVER seen a fluorescent that died cause the phosphor
    got used up. It's ALWAYS been a problem starting...rather not starting.
    I've converted most of my home lighting to CF. The ones that fail the
    most often are the ones that get switched the most...but I think that's
    electronic ballast failure...maybe not relevant data.
    No, if I'd been thinking about incandescent I wouldn't have used the
    word fluorescent.

    Didn't mention it, but the backlight inverter also takes a beating every
    time it turns on. That may be higher failure mode yet.

    mike



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    Return address is VALID but some sites block emails
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    ..
    Wanted, PCMCIA SCSI Card for HP m820 CDRW.
    FS 500MHz Tek DSOscilloscope TDS540 Make Offer
    Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
    Wanted 12" LCD for Compaq Armada 7770MT.
    Bunch of stuff For Sale and Wanted at the link below.
    MAKE THE OBVIOUS CHANGES TO THE LINK
    ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
     
  7. No, I am not working and I am not paid to work.
    The "I see no reason why..." means that I try to help because nobody
    else did, and I know something about fluoroscents, but if you want
    really good, certified answers you turn to somebody else.
    There is vaporized mercury also without the heating. The heating just
    helps it vaporize more, at the ends of the tube.
    That makes it easier to start the current, with lower voltage demands.
    I don't think it matters, but maybe somebody else has a better answer.
    I talked about ageing, not sudden death. Sudden problems are very
    seldom caused by the tube, but rather by the ignition/driver circuit.
    The igniter, if one is used, takes a beating every time you turn on the
    tube.

    In smaller tubes and backlighters I don't think they use the common
    heaters, but rather electronic solutions, and often in smaller
    tubes there is no need for a heater, you just start the current
    through the tube, with a high voltage peak.
    Does changing the tube solve the problem in those cases?
    If so the tubes are worn out somehow. If you need to change the circuit
    the problem lies there.
    How do you know that?
     
  8. mike

    mike Guest

    It takes more voltage to strike the lamp than to run it.
    Higher voltage = more stress???
    mike



    --
    Return address is VALID but some sites block emails
    with links. Delete this sig when replying.
    ..
    Wanted, PCMCIA SCSI Card for HP m820 CDRW.
    FS 500MHz Tek DSOscilloscope TDS540 Make Offer
    Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
    Wanted 12" LCD for Compaq Armada 7770MT.
    Bunch of stuff For Sale and Wanted at the link below.
    MAKE THE OBVIOUS CHANGES TO THE LINK
    ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
     
  9. Do you know the answer to that question?
    That would give both me and you the answer we are looking for.
    Not for the tube, as far as I can understand.
     
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