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Diode? ID

Discussion in 'Datasheets, Manuals and Component Identification' started by corbierev, Dec 21, 2011.

  1. corbierev

    corbierev

    2
    0
    Dec 21, 2011
    Hello all, I'm trying to repair a Makita 24v cordless drill. In the trigger mechanism is a blown (shorted) diode. I say it's a diode but I can't identify it. Cylindrical approx 10mm long by 6mm wide, band and text in blue, S3V7D. Does not come up in any of the searches I've tried!
    Also a blown 100A 60V mosfet, Fuji 2SK3271.
    Will a RS 671-4907 (140A) which is the closest I can get easily be O.K?
    Any info would be greatly appreciated.
    Regards, David.
     
  2. davelectronic

    davelectronic

    1,079
    12
    Dec 13, 2010
    Hello corbierev.
    Welcome from me.
    The normal way is to post a picture of the component, but at a guess there is nothing left of the component to take a picture of, or if there is, posting a picture normally yields better than average results. :)
     
  3. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    I know this is probably not right, but could it be a 37V shottky diode? Do you have a picture of the device in question?
     
  4. corbierev

    corbierev

    2
    0
    Dec 21, 2011
    Diode?

    Thanks for your replies. New to forum and not sure how to reply to you both. Hopefully got pictures posted. Diode cracked but intact. If it's a shotky, is it for a back emf type purpose? It comes into circuit (shorts at present) when the trigger is on full (bypassing the mosfet?). Again thanks for any advice.
    Regards, David.
     

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  5. davelectronic

    davelectronic

    1,079
    12
    Dec 13, 2010
    Its still going to be tricky identifying the exact diode, what part of the drill did it come out of, i guess you clipped the leads, what else was in circuit with it ? can you measure the forward voltage drop using a DMM ? not much information from that, but maybe a step closer . The other components in circuit with it will really help, as in determining the diodes role, it might give clues as to its type and value, is it fast recovery, avalanche, was it used for blocking, and there are others with specific characteristics of some specialized diodes, not often used, but are on occasions. :)
     
  6. davelectronic

    davelectronic

    1,079
    12
    Dec 13, 2010
    Its tempting to say it a silicone 3.7 volts diode, zener , shottky diode, this could mean speed control role, no guessing is no good, see what you can find in my previous post. :)

    PS. A picture of the trigger circuit, or the diodes former place in the circuit.
     
  7. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    Depends on the orientation, if hooked up across the mosfet drain - source it very well could be to protect from back EMF as the circuit is driving a motor. Schematic could help identify its use and help in deciding a replacement. What is the mosfet?
     
  8. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    I agree the diode is probably a 1.4W or so 3.7V zener.
    That RS transistor has a 50% higher on-resistance compared to the original Fuji transistor and so it'll run a little warmer in use.
     
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