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Electronic Ballast

Discussion in 'Electronic Repair' started by Jim M., May 6, 2005.

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  1. Jim M.

    Jim M. Guest

    A fluorescent ballast for my son's aquarium blew a couple resistors. This
    part is built into the cover of the aquarium so I'd rather try to replace
    the blown components than the whole thing. Can anyone assist with
    determining the value of the resistors so I can try replacing them? I can't
    find any info using the ballast model number. The bulb is 8w.

    Picture of ballast:

    TIA! - JIM
  2. I bet more is blown than those resistors.

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  3. James Sweet

    James Sweet Guest

    If you replace the resistors they'll just blow up again. I bet you'll find
    both power transistors are shorted, particularly since they've used wimpy
    TO-92 transistors where big TO-220 cased devices were obviously the original

    Personally I wouldn't even mess with it, you can get a suitable ballast
    circuit board out of a compact fluorescent lamp, or you can get a nice
    electronic ballast on ebay that'll work. I used a Triad ballast designed for
    18W CFL's to replace the shorted chokes in my spa ozonator which has an 8W
  4. NSM

    NSM Guest

    They didn't burn up - they blew like fuses. That's a bad sign.
  5. Jim M.

    Jim M. Guest

    Ok, I'll forget about trying to repair it. Should I use the ballast from a
    9W CFL lamp and/or is it possible to wire two 8W bulbs in series to an 18W
    ballast for double the light?


  6. James Sweet

    James Sweet Guest

    The wattage doesn't quite work like that. Various classes of fluorescent
    tubes are rated at specific currents, and the length of the tube roughly
    determines the voltage across it and hence the wattage it runs at. The
    rating is just nominal, you can under or overdrive them by 10-20% or more at
    the expense of lifespan so it's really not too critical. There's a smaller
    version of this
    which turns up from time to time which would work well for you, it's
    designed for 1-2 16W CFL's, that'd be ideal if you want to run either one or
    two lamps. You can't just run them in series, you won't have cathode heat
    and the tubes will fail soon. Either pull the ballast out of a 9W CFL, or
    find something similar to what I described. If you get stuck I think I have
    an extra one somewhere I'd part with.
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