Craftsman 19 volt cordless drill switch

Discussion in 'Technical Repair' started by tinkerman, Nov 11, 2017.

  1. tinkerman

    Thread Starter Active Member

    Jul 22, 2012
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    I apologize if this is not the right forum to post a question on a variable speed switch in a cordless 19 volt Craftsman 1/2 drill switch.

    Have a drill which suddenly runs only on full speed. Opened and find a transistor??? that is shorted on all three terminals. The numbers are almost impossible to read but have what looks like SK063 V6 in one row. It's mounted on an aluminum heat sink formed around the switch assembly. I'm wondering if it's a MOSFET like this: IRZ44N?

    Can anyone point me to a typical circuit used in these switch applications? Or advise if I'm on the correct path? Should I replace the defective transistor with one listed above?

    The batteries on this drill are long gone and not worth replacing. So it's wired to an to an external 18 volt battery in a permanent application on a sewing machine.

    TIA
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    4,582
    That should work, can you measure or scope the input to the present device to see if there is any control signal? Otherwise a 555 PWM should work.
    Max.
     
  3. tinkerman

    Thread Starter Active Member

    Jul 22, 2012
    144
    34

    I'll try that
     
  4. tinkerman

    Thread Starter Active Member

    Jul 22, 2012
    144
    34
    Closer examination of the chip with powerful magnifier I see what looks like this number:

    P75NS04Z

    Other numbers which appear to be:

    GK06D
    CHN725

    Google search lists P75NS04Z as MOSFET N channel 33 volt, 80 A. TO220 case. Hefty current but I guess a stalled 18 V, 1/2" drill would draw fair current.

    Make sense to you? I have to do the scope thing yet.
     
  5. tinkerman

    Thread Starter Active Member

    Jul 22, 2012
    144
    34
    Yup get square pulses which change width as the trigger switch is depressed. So I'm guessing the internals are working fine.

    Yeah!
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    15,718
    4,582
    So you should be able to get away with just the Mosfet!
    Max,
     
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