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Thread: Problems with BB750 and 5W

  1. #1

    Default Problems with BB750 and 5W

    I have extremly short runtimes with my bb750.
    "extremely" means that with a pack of fresh batteries regulation falls out after ~2 minutes.
    I tried 2 different high-quality sets of batteries.
    If I switch of the light, after it gets dim, and then restart it, it even lights up for only 10 seconds.
    [img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/confused.gif[/img]

  2. #2
    Flashaholic*
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    Default Re: Problems with BB750 and 5W

    You have the same problem I had. The BB750 is very heat intolerant. It shuts down when too hot. The 5W application appears to be right at the ragged edge of one or two components' tolerance.

    You'll need to repot the board with a substance that transmits heat well but doesn't conduct electricity.

    I think my W3V McModule will be my only BB750 5W light, although I might use one for a 1W or 3W.

  3. #3
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    tvodrd's Avatar
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    Default Re: Problems with BB750 and 5W

    There was a discussion here about heatsinking the 750. I was serious about sawing/filing/lapping a copper penny.

    Larry

  4. #4
    *Flashaholic* Rothrandir's Avatar
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    Default Re: Problems with BB750 and 5W

    be warned though, that it's a crime to do that [img]/ubbthreads/images/graemlins/wink.gif[/img]

    instead, you should all ask larry to make us these:


    [img]/ubbthreads/images/graemlins/grin.gif[/img]

  5. #5
    Flashaholic
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    Default Re: Problems with BB750 and 5W

    Pennies havent been made out of copper for a long time they are actualy copper plated zink. Would just hate to see someone go through all that trouble and then find out [img]/ubbthreads/images/graemlins/icon15.gif[/img] with that being said that heat sink looks AWSOME. I gotta have one!

  6. #6

    Default Re: Problems with BB750 and 5W

    thx
    I simply potted the hole thing in arctic-alumina, and then fixed it at the aluminium on the inside of my 3d-mag.
    The contact-area is pretty small, but obviously it is enough to run longer than 6 minutes (didn't have more time to test)

  7. #7
    Flashaholic* Chief_Wiggum's Avatar
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    Default Re: Problems with BB750 and 5W

    Here's what I did. Works great!



    Potted in Arctic Alumina to the back of my 5W heatsink.

  8. #8

    Default Re: Problems with BB750 and 5W

    Chief,

    Could you elaborate a little more. What is the copper looking thing in the picture?

  9. #9
    *Flashaholic* Rothrandir's Avatar
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    Default Re: Problems with BB750 and 5W

    [ QUOTE ]
    dat2zip said:
    ...What is the copper looking thing in the picture?

    [/ QUOTE ]

    i'm guessing copper [img]/ubbthreads/images/graemlins/thinking.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

    very nice job cheif! is the copper heatsink making any contact with the ic?

  10. #10
    *Flashaholic* JonSidneyB's Avatar
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    Default Re: Problems with BB750 and 5W

    hmmm, my BB750 5W seems to be working perfectly

  11. #11
    Flashaholic* Chief_Wiggum's Avatar
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    Default Re: Problems with BB750 and 5W

    It's the copper slug for mounting the 5W. The only thing making contact is the tallest component on the board. I think it's a resistor??? (Not to sharp with electronics [img]/ubbthreads/images/graemlins/grin.gif[/img] )

  12. #12
    Flashaholic* AilSnail's Avatar
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    Default Re: Problems with BB750 and 5W

    How come it looks disformed in the pcb end and discolored in the other? Looks nice, did you turn it on a lathe?

    The tallest thing on the badboys are the inductor but a brown capacitor comes close. It's the two black boxes that get hottest, a diode and an IC.

  13. #13
    Flashaholic* Chief_Wiggum's Avatar
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    Default Re: Problems with BB750 and 5W

    It's disformed, because I made it by hand with a file [img]/ubbthreads/images/graemlins/smile.gif[/img]

    It's discolored because it's actually two pieces of copper soldered together. The silver is the solder.

    So then, the only component in contact with my heatsink is the inductor. The rest transfer heat only with the AA.

    Although, I seem to remember Wayne saying that the BBs don't need much heatsinking, but they do need it.

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