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25-0-25V transformers

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  • 25-0-25V transformers

    I think these came out of Polk PSW-200 subwoofer plate amps that used a pair of the TDA7294's. They are 28-0-28 AC volts unloaded, so they are probably rated at 25-0-25, probably 120VA. Not huge, but good enough for making an honest 100W amp. The voltage is a bit too high for LM3886 amps, but they are fine for the TDA7294/TDA7293.

    I had 8 of them but tried unwinding one to see if it was fairly easy to repurpose the copper wire, which is about 18Ga. Because of the way it is wound, it's not easy to remove the wire--it took way too much time, and I don't see an easy way to do it. I assumed there would be a ferrite core that would break with a few hammer blows, but it's not ferrite--the core is a continuous loop of flat steel ribbon, wound into a donut shape. So I'm giving up on them. If no one wants them, they are going to the scrap yard to get money for the copper.

    You can have them for the cost of shipping plus a small amount for handling (like $5 ea, or $20 for the lot).

    Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

  • #2
    Re: 25-0-25V transformers

    I'll take them Neil. Sent you a PM and e-mail.
    “I cried because I had no shoes until I met a man who had no feet”

    If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

    Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

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    • #3
      Re: 25-0-25V transformers

      I would like 1 or 2, if "thekorvers" doesn't end up taking them all.

      Thanks,
      Paul
      Paul

      The "SB's" build page
      http://techtalk.parts-express.com/sh...-4-(pic-heavy)

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      • #4
        Re: 25-0-25V transformers

        They'd be perfect for LM4780s as well.
        Some people are addicted to Vicodin. I'm addicted to speaker building.

        The Chorales - Usher 8945A/Vifa XT25TG Build
        ESP Project 101 Lateral MOSFET Amplifier
        LM4780 Parallel Chipamp
        Sonata Soundbar Project
        The Renditions - Active/Passive Towers

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        • #5
          Re: 25-0-25V transformers

          Some people collect stamps, Imelda Marcos collected shoes. I collect Polk PSW-200 subwoofer plate amp power transformers.

          I'm going to make cancer-curing electromagnetic necklaces out of them and sell them on ebay.

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          • #6
            Re: 25-0-25V transformers

            Originally posted by jimmy154 View Post
            I collect Polk PSW-200 subwoofer plate amp power transformers.
            I think all of those came in a box of dead amplifiers I bought for cheap on eBay many years ago. I mostly wanted the black hardware, but I've used the binding posts, RCA jacks, volume controls, etc. It was actually a good purchase--it's nice having the parts around when you build amplifiers. I just never got around to reusing the transformers.

            Those toroids are nice--made by Toroid Company in Maryland, and I didn't want to scrap them. But all of the laminated core transformers got whacked with a hammer to free up the bobbins with the copper wire. One of those things you can do while drinking IPA. There are about 14 bobbins in the box:



            If you are still looking for 8" woofers, I've got a box of 4 AR "HO" woofers. I didn't pay a whole lot for them--you can have them for $20 plus shipping, which might be a lot if you are not on the east coast. I'll post some pictures if you are interested.
            Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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            • #7
              Re: 25-0-25V transformers

              When I had my AR308HO speakers in "college", I used to drink a lot of IPA. Harpoon was my favorite, if I remember correctly
              Really loud speakers, especially for their size. Got me arrested one time, if I remember correctly

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              • #8
                Re: 25-0-25V transformers

                I received these yesterday in excellent condition.

                Thanks Neil.
                “I cried because I had no shoes until I met a man who had no feet”

                If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

                Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

                Comment

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