Bulb life - how long do they REALLY last?

Discussion in 'Displays' started by Kenneth Harden, Sep 29, 2004.

  1. Kenneth Harden

    Kenneth Harden Screenwriter

    May 13, 2002
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    I am in the position to get good deals on any sort of TV, but especailly LCD/DLP RPTV (I'm in the industry)

    In general, I have heard the lamps last about 3,000 hours. Does not seem like very long. However, this is for my bedroom and I don't use it a lot. So I did some 3rd grade math.

    For me, lets figure:

    2 hours a day, 5 days a week.

    10 hours a week
    520 hours a year

    So could a lamp actually last me 5+ years!!!??? There would only be one on/off cycle per day, and the TV would be on for an hour or two. So very easy use. Is it possible with easy use, I could get 4, 5,000 hours out of a lamp?

    Just thinking what I want to do.
  2. SimiA

    SimiA Second Unit

    Jul 26, 2004
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    The bulb life of these sets is at most 3000 hours, but with your average usage, the cost p/year of the bulb is minimal.
  3. Leo Kerr

    Leo Kerr Screenwriter

    May 10, 1999
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    Ahh... bulb life.

    [rant]Get over it![/rant]

    Sorry, I'm just a little miffed now by people wondering about bulb life and (the horror!) the expense! A 3000 hour lamp for $500! That's $0.17/hour!

    The project manager at work is screaming at me now because we've got three projectors running 9 hours a day, with 1000 hour lamps that cost $2000/ea. Yik! $2/hour each! Just wait until the next show opens with the $4000 1000 hour lamps...

    Now that I've gotten all that out of the way, let me address some serious comments on bulb life.

    The 3000 lamp life is generally (a) median life, and (b) manufacturer's recommended change point.

    This generally means that in the test lot, that half the lamps were still 'functioning acceptably' at the life of 3000 hours. This also means that if the manufacturer finds that you've over-run the lamp, then they might not warrant ballast or exploded lamp issues. Not that, after five years, the unit'll still be under any sort of warranty.

    What's a bulb like at it's median life? It generally suffers these symptoms:

    1. delayed start-up. The ballast has to work harder to get the initial strike. The 'point' of the cathode (or is it the anode?) 'wears down' and gets harder to spawn the arc. The xenon/argon/mercury mix may have aged, reacted, and/or otherwise decayed inhibiting the starting arc, too.

    2. Slower warm-up. This, I just realized, is the wonder of a true xenon lamp: practically instant on. Most home projectors are a xenon/argon/mercury cocktail. As the cocktail ages and changes through repeated... burning, it takes longer to get the arc atmosphere 'right' for color quality and light output.

    3. Arc instability. This manifests, especially when the lamp is still warming up, as a flicker, either a hot spot, or as an over-all effect. Again, this is related to the condition of both the cathode and the anode, as well as the condition of the arc-environment.

    4. Aged envelope. This is the serious issue. Your standard home projector is probably 1 atmosphere at room temperature. Crank that sucker up, and you're at several atmospheres pressure in the envelope. That quartz envelope will be developing flaws over time from the repeated heating and cooling. Sorry, it's a fact of life. If this becomes a problem, hopefully you'll develop a hairline crack and let the arc envelope cocktail leak out. If this happens, your color goes to snot, along with brightness, and in very short order, you get nothing.

    The other option for the aged envelope is, of course, a snappy little Bang! followed by the tinkling noise of glass bouncing around inside the projector housing.

    This is a bad thing.

    Depending on the design of the projector, and how the lamp explodes, you can get anything from just needing to shake the shards out of the projector, to having a total destruction of the projector's optical system.

    This is why we replace those $2000 lamps at 1000 hours... they are straight xenon lamps, and their room-temperature pressure is ten atmospheres! The lamp is designed so that if it ruptures, it can only go one way. And when it goes there, the first thing it does is destroy the 'integration chamber' where the light is 'mixed' and spread to be fed perfectly equally to the three DLP panels. If that lamp goes Bang! there's a good chance that we need to replace the $30,000 projector. Yik!

    Now that I've tried to humiliate you, scare you, embarras you, and a number of other things, let me give you my advice on using a xenon/mercury/argon short arc lamp. When you think you're getting close, consider the following:

    1. Look at the color. Is it good?
    2. Look at the brightness. Is it good?
    3. Look at the arc stability. Is it good?
    4. If you're brave, pull the lamp. Take a look at the arc tube. Is it distorted? Showing cracks?

    Questions 1-3: if you answer YES, don't worry too much.
    Question 4: If you answer YES, think about worrying.

    I've run 2000 hour lamps close to 5500 hours. It was an old projector; loosely designed, and when the lamp burst, it didn't really care. Changed the lamp, and shook out some of the larger particals. Now, when it burst, the color was horrid, and it was down to about 30% light output. Curiously, the arc was always pretty constant.

    I've also had lamps die due to gradual pressure losses early - 600 hours on a 1000 hour lamp.

    Did any of this help?

    Leo Kerr
  4. Leo Kerr

    Leo Kerr Screenwriter

    May 10, 1999
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    Looking it over in the cold light of morning, I realized I forgot one important point in the above message.

    While I ranted about people complaining about the cost of the lamp, I'm sure that when it comes time for me to replace my own projector lamp at home, that I, too, will be suffering from sticker shock just as bad...


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