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Thread: Casio XJ-A 130 blanking

  1. #11
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    I don't want to be nitpicking here but ...

    Krutz is right, supposing it is a linear current regulator. Seeing that this is such a compact device, the current source will most likely be switchmode.

    Meaning nothing will overheat if you short a diode.

  2. #12
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    I can confirm they are in banks of 6 diodes, in 3x2 arrangements. They are being run constant current in the projector, however the electronics are quite picky about making sure the voltage is in the correct range as well. I haven't had a chance to test it directly, but it will shut down and flash the overheat light of you try to short out a diode. I am working on getting around this however!

  3. #13
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    Quote Originally Posted by krazer View Post
    I can confirm they are in banks of 6 diodes, in 3x2 arrangements. They are being run constant current in the projector, however the electronics are quite picky about making sure the voltage is in the correct range as well. I haven't had a chance to test it directly, but it will shut down and flash the overheat light of you try to short out a diode. I am working on getting around this however!
    My projector operates normally with a blown laser (now an LED). Perhaps I could substitute good laser diodes with blown ones? There will likely be some available soon as more people experiment.

  4. #14
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    Lightbulb

    Quote Originally Posted by krazer View Post
    I can confirm they are in banks of 6 diodes, in 3x2 arrangements.
    ...this may 'shed some light' (photo by others...)



    cheers...
    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  5. #15
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    Cool

    Quote Originally Posted by Krutz View Post
    diodes and LEDs are current-driven, and all diodes (in series) get the same current. when removing any of them (and shorting the "gap"), you will reduce the voltagedrop of the string.
    You are correct. I had erroneously assumed that this used a simple linear voltage regulator, rather than a constant current regulator. My bad.

    Adam

  6. #16
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    I know this is an older thread, but just thought I'd chime in. Any news on replacing a row of laser diodes in the projector?

    I think you 'll have to use regular 1N400x diodes rather than LEDs to replace them. The pulsed current through these laser diodes (measured by krazer) is nearly 1.5 AMPs. LEDs' typical If (forward current) is 20-30 mA. Maybe 50-100 mA if pulsed. Put 1.5 amps through an LED and you get a great flashbulb.

    The Vf (forward voltage drop) of the 445nM laser diodes at that current is close to 5 volts. So, you would need about 7 diodes in series (at .7V drop across each silicon 1N400x) to get 4.9V to be the same as the Vf of the laser diode.

    You might be able to use one of the Luxeon or similar very high brightness LEDs. They have a Imax (max forward current) of nearly 1A. The Vf at this current is about 3.7-4.2 Volts.

    Standard high brightness (blue, white, green) LEDs have a specified Imax of only 30mA, and the Vf at this current is 3.2-3.9Volts.

    --
    Greg
    Those blue photons are the prettiest.

  7. #17
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    There really is no reason to use LED's or dead lasers, a simple diode will work fine. A 1A rated diode would probably work due to the pulsing, but it will get toasty so I recommend using a 3A diode. It should also be possible to get away with just a simple resistor, although due to the different IV characteristics the projector may freak out.

  8. #18
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    krazer, in your post of 6-9, you said:

    the electronics are quite picky about making sure the voltage is in the correct range as well.

    So, I assumed the electronics would complain about seeing 4.2 volts difference (between the 4.9V laser diode, and a .7V 1N400x silicon diode replacement.

    In any case, I think a regular (high intensity) LED running at 1.5amps pulsed wouldn't last very long in there.

    --
    Greg
    Those blue photons are the prettiest.

  9. #19
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    why not a 5 amperes rated zener diode? it would drop the right voltage and cope with the power

  10. #20
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    Quote Originally Posted by shrad View Post
    why not a 5 amperes rated zener diode? it would drop the right voltage and cope with the power
    I believe that this is the best solution, heroic also suggested this in IRC chat (y'all miss out on the good stuff ).

    -Adam
    Support your local Janitor- not solicited .

    Laser (the acronym derived from Light Amplification by Stimulated Emissions of Radiation) is a spectacular manifestation of this process. It is a source which emits a kind of light of unrivaled purity and intensity not found in any of the previously known sources of radiation. - Lasers & Non-Linear Optics, B.B. Laud.

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