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NiCd power tool blown circuit

Discussion in 'Electronic Repair' started by Tibur Waltson, Jan 3, 2004.

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  1. I unscrew and open up a 12V cordless drill and spots what looks like a transistor.
    Hmm..I decide to hook up a 12V 2-amp battery charger into the drill and see what
    happens, unfortunately in reverse polarity. The moment I press the "on" button on
    the drill I see a flash-bang and smoke from the transistor. I thought, "How am I
    going to find a replacement part?" Does anyone know what other transistor is
    compatible with this one? Or, any reverse polarity preventive advice? - as this
    is not my first case.
    TIA
    Tibur
     
  2. Asimov

    Asimov Guest

    "Tibur Waltson" bravely wrote to "All" (03 Jan 04 07:59:00)
    --- on the heady topic of "NiCd power tool blown circuit"

    Is this a troll? No maker, model, nor transistor id, etc? ;-)

    TW> From: "Tibur Waltson" <>

    TW> I unscrew and open up a 12V cordless drill and spots what looks like a
    TW> transistor. Hmm..I decide to hook up a 12V 2-amp battery charger into
    TW> the drill and see what happens, unfortunately in reverse polarity. The
    TW> moment I press the "on" button on the drill I see a flash-bang and
    TW> smoke from the transistor. I thought, "How am I going to find a
    TW> replacement part?" Does anyone know what other transistor is compatible
    TW> with this one? Or, any reverse polarity preventive advice? - as this is
    TW> not my first case. TIA
    TW> Tibur

    .... High voltage can give a dangerously uncomfortable discharge.
     
  3. Sounds to me like you should go play with some guns, so the world will have
    one less idiot to deal with.
     
  4. Chaos Master

    Chaos Master Guest

    Tibur Waltson[] said this in sci.electronics.repair, at Sat, 03 Jan
    2004 07:59:00 GMT, in article
    _I think_ this may be a power transistor. Try using a 2N3055 for a start.

    BTW, is the OP trolling? No model/transistor markings were given.
     
  5. James Sweet

    James Sweet Guest


    Actually if it's in a drill, it's most likely an N channel power MOSFET.
     
  6. I left out the make/model/transistor intentionally, see why. Sorry about
    that. Also posted the wrong voltage. This is an 18V unit. Here's the
    manufacture:

    American Tool Exchange and Chicago Electric Power tools. 1/2" 18V VSR.
    These are two identical drills. Here what it looks like
    http://tinyurl.com/2tlmu

    Reasons for not posting model:

    1. The drill is heavily used and labels regarding models were damaged or
    removed.
    2. The transistor on drill #1 is blown and unreadable. The transistor on
    drill #2 is not blown but has no labels (generic version - made in china.)

    How it works: Inside the trigger handle contains an IC stamp on a tiny
    circuit board with resistors and capacitors. This, I believe, in part,
    controls the power transistor and also reverses the polarity briefly to stop
    the chuck from further spinning when trigger is release. This circuit board
    is not damage, since I swap the power transistors and is working fine. The
    question is what other transistors can take it's place? 2N3055 or an N
    channel power MOSFET or either?
    Tibur
     
  7. James Sweet

    James Sweet Guest


    A 2N3055 is completely wrong, that's a large TO-3 case NPN transistor. Try a
    mosfet, you can't lose by trying, one of the IRF series should work, IRF840,
    820, 740, etc.
     
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