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Help identify transformer

Discussion in 'General Electronics Discussion' started by malomanm, Jan 17, 2015.

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  1. malomanm


    Jan 17, 2015
    First time posting, I'm hoping I can get some info here. My computer subwoofer recently bit the dust, and I narrowed it down to the toroidal transformer. The main winding has an open in it. I'd like to try and identify this transformer to see if replacing it is a viable cost option vs. replacing the whole system. The ink on the sticker is smudged making ID. difficult, but from what I can gather it looks like

    primary winding: 110V AC
    secondary windings: 21V AC (9-21V AC), 0.15V AC

    The primary wires are both red, secondary wires are two blue, two yellow, with a black ground. Is that what it looks like? Apologies on the poor picture quality, I'm having a heck of a time getting the thing out of the box.

    Attached Files:

  2. davenn

    davenn Moderator

    Sep 5, 2009

    I think you have misread that

    it should be 21VAC - 0 - 21VAC blue - black-blue

    ie. its a centre tapped secondary ( 42VAC across the 2 outer wires or 21VAC between either outer and the centretap)

    Yellow - yellow

  3. malomanm


    Jan 17, 2015
    Thanks for clearing that up for me, I'm not experienced with this stuff by any means. Would this be something I could buy off the shelf, or is it more of a custom item?
  4. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    This looks like a Ningbo Wanji Electronics Science & Technology toroidal power transformer. There are two secondary windings. A center-tapped 21-0-21 VAC winding (blue-black-blue) rated at 2.0 A and another 0-15 VAC winding (yellow-yellow) rated at 0.3 A. Good luck finding an American distributor who will sell you one of these OEM transformers.

    OTOH... there are lots of companies who do sell through distributors. You just have to do your due dilligence and find one. Start by looking for a toroidal transformer with similar specifications to the one you have. The exact winding voltage is probably not critical: 24-0-24 VAC would likely work as well as 21-0-21 VAC, but try to find a replacement that is as close to the original as possible. You could also consider having a replacement custom-wound to the same specifications as the original.
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Open circuit primary on mains transformers is often due to a failed thermal fuse. I don't know whether toroidal transformers can be made with thermal fuses - I don't know where you would put one - and the Wanji web site doesn't have much information, but it's a possibility that might be worth checking out, and since the transformer is useless in its current state there's nothing to be lost by undoing the tape and checking the primary connections to see whether they go straight to the winding or not.
    hevans1944 likes this.
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