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Thread: QS FB3 4,2v on modulation, NOT 5v :(

  1. #1
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    Default QS FB3 4,2v on modulation, NOT 5v :(

    Hi All,

    Just testing FB3 QS (usb) voltages for red/green/blue analog modulation on ILDA card and voltage is "only" 4,2v per color at full power (full brightness settings, full scale etc), NOT 5v
    Cause my Ld's drivers are adjusted for 5v modulation for full power, I can't obtain full laser power with ILDA on this config.

    I had to retouch bias/current trimpots on my laser drivers to obtain full laser power with 4,2v modulation, but this is annoying.

    My FB3 is connected to macbook pro running Windows 7 on parallels.

    Anyone knows why this happens?

    Many thanks!!

  2. #2
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    Default

    What device are you using to measure the voltage? An oscilloscope or a multimeter?

  3. #3
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    Maybe there is a problem with the fb3 but ! You must not adjust your driver at 5v for full modulation, due to loss in the ilda cables 4,5v seems better.
    And yes you have to use an ocilloscope to mesure ilda output.

  4. #4
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    Thanks for responses. I'm using multimeter. There is no IDLA db25 cable loss due FB3 is attached directly to ILDA card inside projector. Here are some pics:Click image for larger version. 

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  5. #5
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    These outputs can not be reliably measured with a multimeter; the results are essentially meaningless.
    As mentioned earlier you need to use an oscilloscope.

    Also... you don't need to see 5V on the modulation lines; most, if not all drivers provide full current / saturate with ~4.5-4.7V applied to the modulation input.
    - There is no such word as "can't" -
    - 60% of the time it works every time -

  6. #6
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    After re-adjusting drivers trimpots I can get full power at 4,2v modulation, but...what happens if projector is connected to other ILDA at 5V? could I fry my LD's?
    Anyway I'm happy with 4,48W laser power out of the box, considering that every color is cylindrical lens corrected. Why use oscilloscope? please, could you tell me?
    many thanksClick image for larger version. 

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  7. #7
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  8. #8
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    Want to share some pics )
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  9. #9
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    Daniel,
    When testing, I applied 5V (not ilda) and adjusted for max current.
    With Ilda, I measured current again on drivers and was rather less.

    so I re-adjusted all drivers for full power at "4,2v". Is that ok?

    many thanks

  10. #10
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    so, oscilloscope or not, there is really less laser power/driver LD current on ILDA than directly 5v

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