scope tech li-ion charger help

Discussion in 'The Projects Forum' started by maxs, Nov 30, 2012.

  1. maxs

    Thread Starter New Member

    Aug 5, 2009
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    this charger belongs to a guy i work with he asked me to see if i could fix it for him ...

    well i disassembled it and found q4 on the pcb burned out but have no idea what the part is its burned to bad ill attach a pic and hopefully someone here could shed some light on what this part is

    the charger is a scope technology co. ltd. li-ion battery charger wall mount model dj04v20500a

    cant find a schematic anywhere dont know why he wont buy a new 1 probably strapped for cash i understand that in this day and time anyway hope someone can help thanks

    maxs
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,126
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    The best thing would be to find another one or a schematic. That picture certainly doesn't help much.

    If you have to resort to brute force, you might just assume it's an NPN and try one at random. If it doesn't work, try a PNP.

    Something caused it blow, though, so I would really think twice about whether this is worth pursuing. You can buy replacement chargers under $10 these days.
     
  3. maxs

    Thread Starter New Member

    Aug 5, 2009
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    yeah i know there pretty cheap i may just buy him one for xmas but i still would like to at least see what this tranny was and why it blowed its peeked my intrest

    but a schematic i cannot seem to find but ill keep looking thanks for the reply
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I did a web search and could not find the company or the product.
     
  5. #12

    Expert

    Nov 30, 2010
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    That board is small enough that you could trace it out and make your own schematic. It is only for educational purposes because it will take a LOT more time than $10 worth! I've done it many times, so don't think I'm calling you a fool. It is very educational.

    Psychic prediction: The transistor fried because the battery went bad and the manufacturer did not provide protection against that sort of overload.
     
  6. maxs

    Thread Starter New Member

    Aug 5, 2009
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    makes sence ive seen laptops explode when on charge when the battery shorted although they do have some protection built into them but it still happens
     
  7. maxs

    Thread Starter New Member

    Aug 5, 2009
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    run a search on this SCOPE TECHNOLOGY DJ04V20500A that is the model number
     
  8. wayneh

    Expert

    Sep 9, 2010
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    That's not a bad idea, and like #12 I've done this for things worth less than your charger. As he notes, you have to want to do this exercise for its own sake. You could not afford to pay anyone a wage to do it for you, for less than a new one.

    The schematic would likely reveal what general type of transistor to try, NPN or PNP, BJT or MOSFET. It might also reveal what the likely failure was.
     
  9. bountyhunter

    Well-Known Member

    Sep 7, 2009
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  10. maxs

    Thread Starter New Member

    Aug 5, 2009
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    its goin to be fun but at least i may find out what and mabe why this tranny burned out at first i was thinking power surge till i looked a little closer the reverse side shows no signs of overvoltage has a few can style caps some of which should have probably swelled or burst has a small freqnency transformer not hurt that i can see. its going to be slow though...
     
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