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Problem with Makita 18v Cordless drill

Discussion in 'Tools and Materials' started by peweuk, 9 Sep 2019.

  1. peweuk

    peweuk

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    I have a Makita 18v LXT li-ion cordless drill which has suddenly stopped working.
    The battery is fully charged but there does not appear to be power getting to the brushes.

    I am wondering if it could be something to do with the sensor (labelled FET in the attached schematic) which is attached to the heatsink and wired to the trigger - but I'm not sure how this works so don't know how to test it.

    Anyone any thoughts?

    makita drill wiring.jpg
     
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  3. nickjb

    nickjb

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    The FET isn't a sensor its a transistor which does the speed control. Could be that or maybe the switch. The fet gets a variable voltage in from the switch and high power connection to the brushes. Should be able to check it with a meter. That said you can buy a whole be bare drill for around £30 so its not worth spending too long and throwing parts at (other than the satisfaction of fixing it)
     
  4. peweuk

    peweuk

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    Thanks for the explanation.
    The drill is about 15 years old - although hasn't been heavily used - so if I can get a body for around £30 I'd do that, but when I searched the results were closer to th £80-£90 mark.
    Where would I find them at the price you mention.
     
  5. nickjb

    nickjb

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    For shops FFX are pretty good (although a very quick google has them at £42) or PowerToolWorld. Plenty on ebay at £30. That'll likely be the most basic model. Its not a big leap to the brushless model at around £70 which is quite a bit better
     
  6. peweuk

    peweuk

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    Thanks, I search again.
    In the meantime, is it possible to re-wire the drill to eliminate the variable speed and just wire the trigger straight to the brush assembly - would this work?
    If so I could use the drill as a backup.
     
  7. JobAndKnock

    JobAndKnock

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    A lot of the usability of cordless drill/drivers surely comes from the fact that they are variable speed and soft start, so if you were to wire one in maximum speed mode you'd certainly lose the ability to drive screws. One thing I'm not sure about is where the braking function is. Normally with a cordless when you take your finger off the button the power to the motor is not just cut, but the motor is additionally braked to a halt
     
  8. peweuk

    peweuk

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    I understand what you are saying about the usability, but having just bought a replacement body it would be useful if I could just run the faulty one as a backup drill just for drilling.
     
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