How do you know if the lamp has died?

Discussion in 'Projectors, Screens & Video Processors' started by Skyav, Mar 28, 2006.

  1. Skyav

    Skyav
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    Hi all,

    After almost 2 years and just over 1000 hours, the lamp on my lovely Optoma/Themescene H30 has, sadly died.

    The lamp failed to strike on one previous occasion, so I returned it and apparently it was a fault with the projector, so it was fixed and returned no problem.

    This time around, exactly the same thing happened - it failed to strike up, but there was no dimming, no cracking or popping sound, nothing to indicate a faulty lamp - yet Optoma tell me the lamp needs replacing.

    I guess my question is - does that sound normal? I'm not at all suggesting that Optoma are just angling for me to shell out £300 for a new lamp, but it would be good to know of anyone elses' experience of faulty lamps and whether they exhibited any unusual behaviour before dying.

    It would be handy to know - for example - if you remove the lamp would it look burnt out or broken? It would at least prevent me having it sent to Optoma for no reason should I ever have the same problem...

    Cheers,

    Skyav:thumbsup:
     
  2. laserdave

    laserdave
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    Unfortunatly a casual inspection of the lamp will not tell you much as it would for a filament bulb, but the bad signs are

    1) Excessive metal spatter and discolouration of the quartz ( a small amount is normal say 5-10% coverage) if the quartz is totally covered in a milky red/yellow gunk then i`d recomend replacing the lamp

    2)If you can see through the quartz envelope and have a decent magnifier, check that both electrodes are still there ( one will be slightly thicker than the other) and are about the same length and are sitting at about the same angle (i.e. not wilted from heat/stress)

    These are observations from failed MSR/HMI/Xenon/CSI short arc`s and should hold true for UHP`s

    BTW UHP drive electronics send a modified voltage wave to the lamp to keep the arc steady ( as the QC ballasts on some of the kit at work) so the lamps tend to fail on striking or just shut down, there is no tell tale flickering or sputtering until a few seconds before they die.

    Hope this helps

    Dave
     
  3. laserdave

    laserdave
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    One of the guys at work today said that it may be interesting to explain the gunk that lines the lamp.....:lesson:

    The quartz envelope contains a mettalic vapour (UHP/HTI/MSR etc) that when new is only faintly visable upon the envelope itself, as the lamp ages tungsten from the electrodes begins to join the metal spatter on a cold lamp the more the spatter the more hours on the lamp......

    However there is a fill of a halogen (iodene/bromine) that combines with the tungsten when the lamp is at operating temperatures and will redeposit the tungsten back on to the electrodes (without getting to technical this is the halogen cycle mentioned on the lamp spec sheet), the milky deposit on the lamp is the tungsten or mercury halide which has not had a chance to recombine whist the lamp is running as stated before if this is a small amount then there is no problem as the lamp will re-absorb this upon the next start up / running hours. Unfortunatly the high temperatures/ pressures within short arc lamps will cause some of the fill getting absorbed into the quartz enevelope where it will no longer get recycled by the halogen(spatter) or the halogen itself will get "laminated" to the quartz and no longer able to recycle the tungsten (red/yellow milky coating)

    Thats it its getting boring now:boring:

    Dave
     
  4. Skyav

    Skyav
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    Cheers for that, LaserDave - I should be getting my H30 back within the next day or two, and they said I could keep the old lamp...so I'll have a good close inspection!

    :thumbsup:


    (300 quid....ouch :( )
     

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