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MP-3314 multi-voltage plugpack - fails under load

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    MP-3314 multi-voltage plugpack - fails under load

    I know these things are only worth a few dollars, so this is perhaps more an intellectual exercise in understanding what is (not) going on here.

    The model is marked as MP-3314, sold in our consumer electronics stores, and is variable between 3V and 12V at 1.5A.

    Under no load it shows as the appropriate voltage - set currently at 9V. But under load it fails, the LED flashes/blinks as it tries to restart. Meter shows volts come up but fall back with a fraction of a second, repeated continuously.

    What would be a typical component that would fail, producing this effect?

    Images attached of both sides of board.

    By the way, have confirmed the device it is driving is OK. I have wired in my bench variable supply and all works 100%
    Attached Files

    #2
    Re: MP-3314 multi-voltage plugpack - fails under load

    3v @ 1.5A
    probably means 6v @ 750mA and 12v @ 375mA

    whats your load and where is the primary's heatsink?

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      #3
      Re: MP-3314 multi-voltage plugpack - fails under load

      There is a small value electrolytic in the primary I would replace first, In your picture it is the one located next to the transformer below the mosfet.
      Attached Files
      Last edited by R_J; 02-19-2022, 09:02 PM.

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        #4
        Re: MP-3314 multi-voltage plugpack - fails under load

        clean the solder side of the board and resolder the bad joints

        Comment


          #5
          Re: MP-3314 multi-voltage plugpack - fails under load

          Originally posted by stj View Post
          3v @ 1.5A
          probably means 6v @ 750mA and 12v @ 375mA

          whats your load and where is the primary's heatsink?
          It's driving one of these cheap and nasty Chinese all-in-one Hi-Fi (actually Lo-Fi) units with a turntable, CD player, radio. The specs on the unit say 9V @1500mA.

          And what you see in the images is what you get. No heatsink to speak of.

          I think you are probably correct. Simply can't supply the required load.

          I found a 12V 2A plugpack in my junkbox and gave that a go. It powers up and runs. But there is a oscillation tone coming from the speakers that is reasonably prominent. Hard to image that 3 volts would make much difference? But I certainly didn't hear any of that when I was running it off 9V from my bench supply. Just cheap and nasty electronics all around I suspect.

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