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Power Supply Wizards?

Discussion in 'DIY' started by Chilibrother, Dec 6, 2018 at 3:20 PM.

  1. Chilibrother

    Chilibrother AK Subscriber Subscriber

    Messages:
    81
    Location:
    Kansas
    Getting cold, so naturally I'm already planning for Spring. I want to replace the ridiculously oversized AVR I use as the patio stereo and was thinking about one of the little (and cheap) Lepai amps. I know I would want something better than the wall wart as a PS.
    Lo and behold a local going out of business sale had a NIB 12VDC 1.8AMP x 2 regulated power supply. Seems well built and it was only two bucks. Manufacturer's website no longer recognizes it, so it's out of production and I can't find any documentation.

    Just two (maybe boneheaded) questions. On the transformer primary I'm assuming that leads 1/3 and 2/4 are the 110VAC inputs and 5 is for the ground.
    IMG_1025.jpg
    Now on the outputs. It's a dual output power supply. Two terminals labeled Common and two outputs - but one labeled +Out and one labeled -Out. I would assume that Commons are negative. Why is there an output labeled "-"? I would like to like to bridge the two supplies in parallel to have 3.6 amps. That would give me 40 watts of output on the Lepai. My inclination would be to tie the two commons together and the two outputs together to get 12VDC @ 3.6A but labeling one of the outputs as negative is throwing me off. Or maybe I use the two output terminals to get 24VDC by running the two supplies in series? What am I missing? Thanks for any thoughts.

    IMG_1027.jpg
     

     

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  2. dB happy

    dB happy Active Member

    Messages:
    230
    I don't think you'll be able to parallel the outputs because of the design. You'll probably get 24v @1.8a if you measure between the positive and negative outputs. Common would be positive for the negative out, and negative for the positive out. Pretty sure they're wired in series.

    I'm guessing the transformer is wired for 120v in, probably just hook power to each pair of joined terminals. Is there any useful info on the sticker?
     
  3. Lavane

    Lavane AK Subscriber Subscriber

    Messages:
    7,551
    Location:
    northern cal.
    Do you have any of those "brick" power supplies from an old laptop laying around? You could probably find one at the output voltage needed. Goodwill usually has a pile of them. Better filtered than a wall wart along with more current available.
     
  4. Chilibrother

    Chilibrother AK Subscriber Subscriber

    Messages:
    81
    Location:
    Kansas
    Yep - should have mentioned that. The sticker says that input is 115VAC @ 1A - just wanted to make sure I wasn't doing anything goofy in wiring it. Once I do that then I can measure the outputs. If the two outputs measure 24V across them then I'm golden since the Lepai will take up to 24VDC. At 1.8 amps that would give me the 40 watts I'm looking for. Thanks!
     
  5. Chilibrother

    Chilibrother AK Subscriber Subscriber

    Messages:
    81
    Location:
    Kansas
    Thanks. I will keep that as a fallback idea - I have lots of those! Actually, this PS looks like one that someone building their own PC might use.
     

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