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Thread: A140 or P3 issue?

  1. #1
    Join Date
    Jun 2010
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    Syracuse, NY
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    287

    Default A140 or P3 issue?

    Up until a few days ago I had typically been running an A140 diode @500-550mA via a Flexmod P3 for a lumia setup. I hadn't driven it any higher than that but decided last week that I would turn it up to see what kind of power the diode actually outputs. I turned it up to about 850mA no problem but then disconnected it from power to move a few things around on the mounting board. When I connected it to power again the diode would flash twice and go out. The first flash would be significantly brighter than the second flash but then nothing. disconnect and reconnect power to try again and I get the same result. The only solution is to turn the current down to <500mA for the diode to lase again. Once the diode is lasing I can turn the current back up to 850mA but as soon as power is disconnected and reconnected the diode only flashes twice before going out. I need to turn the current back down in order to get it working again. I'm not sure if this is a possible issue with a bad connection to or from the driver or if it's an issue with the diode. All the connections appear solid as far as I can tell. I hear all sorts of talk from people about them driving these diodes to 1.2-1.4A without issue so I can't believe my 850mA was causing an issue but I can't be sure. I couldn't detect any significant heat from the mount that would indicate a thermal issue. Has anyone experienced this sort of thing before?
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  2. #2
    Join Date
    Dec 2006
    Location
    denver,co
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    1,078

    Default

    A couple of things to look at.

    1) what voltage are you giving the P3?
    2) How much current is your power supply good for?

    This sounds to me like a powersupply that doesn't have the balls to drive at higher power levels.

    chad


    When the going gets weird, the weird turn pro.


  3. #3
    Join Date
    Aug 2008
    Location
    Seattle
    Posts
    220

    Default

    Quote Originally Posted by chad View Post
    A couple of things to look at.

    This sounds to me like a powersupply that doesn't have the balls to drive at higher power levels.
    A good candidate for root cause. I saw similar behavior from four diodes I was driving with two P3's supplied by a 12V PSU that didn't supply enough current.

  4. #4
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    When you disconnect a LD from a CC power source (depending on the source) it will ramp up the V to try to satisfy the current requirement. Make sure that there is no voltage present on the pins going to the LD when reconnecting. Not sure what your particular problem is, just a note of precaution. I've killed a LD that way before, forgetting to do that. A bleed-off resistor is also good just for the absent-minded (like me)

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