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power choke?

Discussion in 'General Electronics Discussion' started by fosgate3, Mar 15, 2011.

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  1. fosgate3

    fosgate3

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    Mar 15, 2011
    First I want to say hello. I'm new to this forum and this is my first post. I am not that experienced with electronics and circuit---knowing enough to set fire to something and that maybe it! LOL actually, I know a little and can do some repairs on a few things but I'll be the first to admit that my limit is there.

    I have a Sangean ats-818acs shortwave receiver that seems to have a bad radial power choke on the back of the circuit board. I want to replace it but the choke has no markings on it so I'm not sure what exactly to replace it with. Is there a way to find out what I should use to replace it with or would I simply go back with a choke that is the same size.

    Thanks for taking the time to read this. I apologize up front if my question is elementary.
     
  2. rob_croxford

    rob_croxford

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    Aug 3, 2010
    Hi and welcome to the forums :)

    Generally (as far as i kno) chokes are used mainly for the purpose of eliminating high frequiencies and allowing low frequencies or DC to pass. However they are all rated for different applications. There should be markings showing the inductance (probably in mH) and the current rating (in Amps).
     
  3. fosgate3

    fosgate3

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    Mar 15, 2011
    Thank you rob.
    I was thinking that there would be markings as all other situations I've seen, I've found markings on whatever it was that I was looking at. On this piece, there is nothing discernible on the plastic coating the choke, even under magnification. That actually was my first check. :)

    I am at work right now and was making this post in my spare time. When I get home, I will search again under magnification to find something that will guide me.
     
  4. rob_croxford

    rob_croxford

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    Aug 3, 2010
    Sorry i did not read your post properly saying that there were no markings!!

    Generally you should be able to figure out a replacement (based on the current and voltage of your circuit)

    Do you know what kind of choke it is?? Solid state (generally for high currents) or comon mode chocke (gernally for the prevention or electro-magnetic interferance)
     
  5. fosgate3

    fosgate3

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    Mar 15, 2011
    No I don't. It's actually soldered to the backside of the circuit board. When the radio is on and you press against it, the reception volume becomes very weak. Because it's on the back of the board, it was pressed between the board and the case of the radio. This caused a broken solder joint which I fixed. I thought it was all working well but then noticed that something was still amiss when I picked up the radio and applied pressure to it while holding it and while the radio was on.

    I could take and post a picture of it this evening, if that would help.
     
  6. rob_croxford

    rob_croxford

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    Aug 3, 2010
    Yea see if you can post a picture from the top and bottom of the board :)
     
  7. fosgate3

    fosgate3

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    Mar 15, 2011
  8. rob_croxford

    rob_croxford

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    Aug 3, 2010
  9. fosgate3

    fosgate3

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    Mar 15, 2011
    Thanks! I will read through it and will post some pictures this evening.
     
  10. fosgate3

    fosgate3

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    Mar 15, 2011
    I pulled up the schematic in that link I just posted and then enlarged it. I found the symbol for an inductor over in the upper right hand corner of the schematic. It looks like 2.2mH. I did a search for that in google images and found this: http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=13r225c
    That looks identical to what I have. I just don't know the amperage.
     
  11. rob_croxford

    rob_croxford

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    Aug 3, 2010
    0.24A - that sounds about right :)
     
  12. fosgate3

    fosgate3

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    Mar 15, 2011
    Excellent. Thank you for your help. You made this easy.
     
  13. rob_croxford

    rob_croxford

    262
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    Aug 3, 2010
    no problem i hope you get it fixed :)
     
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