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Thread: Casio XJ-A 130 blanking

  1. #1
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    Default Casio XJ-A 130 blanking

    Perhaps this is buried in one of the other threads, please direct me if I missed it. I am wondering if it would be possible to only harvest the top row of the laser block then picture adjust a wide screen image downward to still have a usable picture. Or if there is some sort of shut down circuit could it be fooled by using just a silicon diode in place of the laser diodes? Since it is a native 4:3 it seems that widescreen would just be blanking (video term) the top and or bottom anyhow. thoughts?
    leading in trailing technology

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    totally random guess: by removing individual diodes you would only lower the total brightness, not get some dark areas on your screen. all diodes' output are focused to a relatively small area on the phosphor, thats what makes me believe this.

    I read in one of the many posts that the projector doesnt like it when all diodes are removed. it will probably complain if any of the "rows" of diodes is removed too. good idea to replace it with a similar diode: I would suggest LEDs, for their large voltagedrop and high power-input (you will need to dissipate the original electrical input of the laserdiodes in whatever you replace them with)

    curious what will form from this idea!

    manuel

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    The diodes are wired in series. You'd need to replace them with resistors (or better yet, more diodes with similar voltage-drop characteristics) in order to get it to function.

    Adam

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    And if an entire series circuit of six were removed? Does that translate to left, right, top, bottom, or does it even matter? Because I've heard the beams are sent through translucent glass to even it out anyway.

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    My new projector had a dead laser right out of the box. I don't see any irregularities in the TV picture with either white or blue screens. Would like to remove a few more lasers. What should go in their place?
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  6. #6
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    Quote Originally Posted by Photonbeam View Post
    My new projector had a dead laser right out of the box. I don't see any irregularities in the TV picture with either white or blue screens. Would like to remove a few more lasers. What should go in their place?
    take it back and ask for another projector...that is a $50.00 pointer sale right there!

    why would you want to replace them...arent you going to scrap the whole mother?
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    Quote Originally Posted by Laserman532 View Post
    take it back and ask for another projector...that is a $50.00 pointer sale right there!

    why would you want to replace them...arent you going to scrap the whole mother?
    Probably voided warranty by opening it. How would a customer know there is a dead laser without opening the device?
    I will harvest 4-6 lasers and see if it still projects acceptable video. What should go in place of the missing lasers to fool the electronics? Short? Resistor? Diode? LED?

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    Quote Originally Posted by Photonbeam View Post
    My new projector had a dead laser right out of the box. I don't see any irregularities in the TV picture with either white or blue screens. Would like to remove a few more lasers. What should go in their place?
    I wonder what the average failure rate is. Hopefully people harvesting can safely power up prior so they know all diode were good prior to shipping.
    leading in trailing technology

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    Quote Originally Posted by Photonbeam View Post
    What should go in place of the missing lasers to fool the electronics? Short? Resistor? Diode? LED?
    Don't short it! Remember, they're in series. If you short one, the voltage that would have been dropped by that diode will be split among the others, causing them to draw *significantly* more current. You'll likely blow the rest.

    Not sure if all 24 are in series, or if they're in 4 banks of 6 diodes each, but either way, shorting across one diode is a sure-fire way to kill many diodes.

    If you know the voltage drop across one laser diode, you can approximate that with a few standard diodes in series, but be mindful of the current they'll have to pass. An LED would also work, but since the voltage drop will be lower for the LED than for the laser diode, again you'll need more than one.

    Alternately, you can measure the current (with an oscilloscope, since it's pulsed), and from that you can calculate how much resistance you'll need to get the same voltage drop. Then you can install the correct-size resistor. But again, be mindful of the current. Make sure the resistor can handle the power. (Probably going to need a 5 watt resistor, and to be safe I'd go with a 10 watt one.)

    Adam

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    actually no, it wouldnt blow the left diodes. 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. the diodes get the same, constant current and are fine. the "missing" voltagedrop from the removed diode will have to be dropped in the constant current source (transistor, FET). so the energy taken up by the diode (heat and optical output) will be heat and overcurrent in that transistor, and at one point blow it. insert a LED to drop the voltage and the current source wont see a difference.

    manuel

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