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Infocus projector

Discussion in 'Electronic Repair' started by tlfort, Oct 8, 2003.

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  1. tlfort

    tlfort Guest

    I have a replacement lamp for an infocus projector. I would like to
    check it to see if it is good. I used an ohmmeter to check across the
    terminals but it registers open. I actually think that this is an a/c
    bulb of some sort. I was wondering if I could just put 115v across the
    terminals to check it. The bulb looks brand new and is supposed to be
    good. I don't know the voltage rating of the bulb, but I'm sure it has
    to be A/C. The bulb is 200 watts output. Is it possible for the bulb
    to be some kind of funky gas discharge bulb that would show open with
    an ohmmeter when the bulb is good?

    thanks,
    Tracy
     
  2. You can't check it easily.

    It's a high intensity discharge lamp and requires something like
    30 kV to initiate the arc.

    Even if you pull the back off your projection TV and apply its 30 kV
    across the lamp and it flashes, still doesn't mean it's good. :)

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: The email address in this message header may no longer work. To
    contact me, please use the Feedback Form at repairfaq.org. Thanks.
     
  3. Tim Mitchell

    Tim Mitchell Guest

    Yes, they usually are.

    They need special control gear to make them work. Probably the only way
    to test it is to fit it to the projector and see if it works.
     
  4. red

    red Guest

    You cant check with an OHM meter. Like everyone has said you have to put it
    in the projector. If it is a new replacement lamp it shold be good. Some
    lamps have fuses on the housing assembly. Check that. What model it the
    projector? (infocus sucks anyways) Make sure the projector hasn't exceeded
    tha lamp life. It may be in internal shutdown which requires you to reset
    the lamp timer.
     
  5. Jerry G.

    Jerry G. Guest

    If this projector is the one that looks like a big clamshell, and was also
    distributed by Electrohome in Canada, the following below would apply.

    I was working for a place that had one of these projectors, among a number
    of different types, for doing special shows. I used to do some of the
    service on this projector type. If I remember correctly, this is a Xenon gas
    discharge lamp. It used a very high current type high voltage, high
    frequency pulse supply. It was in the order of about 5,000 Volts. You cannot
    test this type of lamp without running it in the proper supply, proper
    safety enclosure, and proper high pressure cooling. Its rated life span was
    about 900 hours, but we have never seen one go for more than about 250
    hours.

    When firing up the lamp, there cannot be any finger prints, any dust, or
    dirt on it, or the lamp will crack when operated. Finger prints must be
    cleaned off with pure alcohol only.

    This lamp is very high on medium to short-wave (UVB-UVC) UV output, and when
    operated, the projector has some UV filtering incorporated in to the optical
    elements that the light passes though. This is essential for this type of
    lamp to meet safety regulations for viewing projected pictures that use this
    type of lamp as the light source. Invisible reflected UV rays are also very
    dangerous to the eyes.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    Instruments http://www.zoom-one.com/glgtech.htm
    =========================================


    I have a replacement lamp for an infocus projector. I would like to
    check it to see if it is good. I used an ohmmeter to check across the
    terminals but it registers open. I actually think that this is an a/c
    bulb of some sort. I was wondering if I could just put 115v across the
    terminals to check it. The bulb looks brand new and is supposed to be
    good. I don't know the voltage rating of the bulb, but I'm sure it has
    to be A/C. The bulb is 200 watts output. Is it possible for the bulb
    to be some kind of funky gas discharge bulb that would show open with
    an ohmmeter when the bulb is good?

    thanks,
    Tracy
     
  6. Isn't there also a concern that as the lamp ages, the pressure inside goes up
    or the envelope becomes more brittle or something.

    Lamp life is not only limited by electrical considerations but also by the
    explosion hazard. I don't know if there's a way to determine if a lamp
    is safe to use other than by number of hours it has been in use.

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: The email address in this message header may no longer work. To
    contact me, please use the Feedback Form at repairfaq.org. Thanks.
     
  7. kc8adu

    kc8adu Guest

    the chance of a violent explosion increases sharply near end of life.
    hence the timer.
     
  8. Jim Adney

    Jim Adney Guest

    What would make the pressure go up?

    Don't high temps usually anneal glass, making it less likely to break?
    Is this also true for quartz?

    -
     
  9. kc8adu

    kc8adu Guest

    these are under very high pressure cold.
    this increases as it heats up.i bet the metal sputtered off the electrodes
    blackens the arc tube and makes it run too hot.
    this makes the pressure go up.
     
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