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    Laptop power brick audibly noisy

    I wired this up with a apple airport cable so it would fit my Pinecil soldering iron and not have a stupid heavy ferrite bead at the end near the plug. The noise changes depending on the load. With a 9w load it's less frequent and with a laptop 50w+ load it's higher pitched. If I press on the transformer with something plastic it also gets a little quieter. Any danger here? Am I actually hearing the switching of the FET? It's like tapping not really squealing like coil whine.

    I realize it's probably a low end little brick but it came apart super easy without any cracking or melting of the case so I decided to use it. I probably have a dozen other 19v 3a bricks I could use instead if this is a hazard.
    Attached Files
    Last edited by jayjr1105; 03-09-2022, 09:56 AM.
    --------------------------------------------------------------
    Ryzen 3600x
    16GB Patriot 3600MHz
    MSI B450 Gaming Plus
    MSI Air Boost Vega 56
    Acer 32" 1440P Freesync
    Rosewill Capstone 750W
    --------------------------------------------------------------
    Hakko FX-888D Station
    FX-8802 Iron
    MG Chem .8mm 63/37 RA 2.2%

    #2
    Re: Laptop power brick audibly noisy

    well squeeling is often bad caps early on.
    in this case i would get shot of that bs mylar snubber cap and fit a 2KV ceramic - while it's out you can check the associated resistor

    Comment


      #3
      Re: Laptop power brick audibly noisy

      Definitely not cap squealing. It's coming from the transformer it would seem. It's like a soft rapid tapping.
      --------------------------------------------------------------
      Ryzen 3600x
      16GB Patriot 3600MHz
      MSI B450 Gaming Plus
      MSI Air Boost Vega 56
      Acer 32" 1440P Freesync
      Rosewill Capstone 750W
      --------------------------------------------------------------
      Hakko FX-888D Station
      FX-8802 Iron
      MG Chem .8mm 63/37 RA 2.2%

      Comment


        #4
        Re: Laptop power brick audibly noisy

        Originally posted by jayjr1105 View Post
        Definitely not cap squealing. It's coming from the transformer it would seem. It's like a soft rapid tapping.
        I think that's normal?
        Reason I say that is because my Aoyue 2900 soldering station does the same thing - sounds like light tapping/clicking, and it is synchronized with the PWM pulsing of the station's tip-diving MOSFET. And likewise, the sound is coming from the transformer on the station... though in my case, it's worth noting that the 2900 / CS2900 uses a classic line-frequency transformer rather than an SMPS.
        In any case, though, I've had that station since ~2012. So if it hasn't failed after 10 years, I suppose it's OK.

        Originally posted by jayjr1105 View Post
        I realize it's probably a low end little brick but it came apart super easy without any cracking or melting of the case so I decided to use it. I probably have a dozen other 19v 3a bricks I could use instead if this is a hazard.
        It looks OK.
        Transformer looks big enough and also probably has OK primary-secondary insulation.
        Seems like you've already recapped it with good caps (minus the mains, but that's probably OK for a good while usually.) Therefore, I don't expect you'll see any major failures, if at all.
        As long as the adapter uses some kind of current-mode PWM controller to drive that MOSFET on the primary, it should be decently safe enough to use. But if it's a 2-transistor self-oscillating design, I'd definitely not advise to leave it plugged in unattended.

        Comment


          #5
          Re: Laptop power brick audibly noisy

          Originally posted by momaka View Post
          I think that's normal?
          Reason I say that is because my Aoyue 2900 soldering station does the same thing - sounds like light tapping/clicking, and it is synchronized with the PWM pulsing of the station's tip-diving MOSFET. And likewise, the sound is coming from the transformer on the station... though in my case, it's worth noting that the 2900 / CS2900 uses a classic line-frequency transformer rather than an SMPS.
          In any case, though, I've had that station since ~2012. So if it hasn't failed after 10 years, I suppose it's OK.


          It looks OK.
          Transformer looks big enough and also probably has OK primary-secondary insulation.
          Seems like you've already recapped it with good caps (minus the mains, but that's probably OK for a good while usually.) Therefore, I don't expect you'll see any major failures, if at all.
          As long as the adapter uses some kind of current-mode PWM controller to drive that MOSFET on the primary, it should be decently safe enough to use. But if it's a 2-transistor self-oscillating design, I'd definitely not advise to leave it plugged in unattended.
          It seems to have quieted down a little but still that light tapping. I've actually used it for the past couple days to power an old 2010 laptop which I use for my USB microscope and no issues. It gets warm but that's with a 40-50w load. How can I tell if it's a 2 transistor self-oscillating design?
          --------------------------------------------------------------
          Ryzen 3600x
          16GB Patriot 3600MHz
          MSI B450 Gaming Plus
          MSI Air Boost Vega 56
          Acer 32" 1440P Freesync
          Rosewill Capstone 750W
          --------------------------------------------------------------
          Hakko FX-888D Station
          FX-8802 Iron
          MG Chem .8mm 63/37 RA 2.2%

          Comment


            #6
            Re: Laptop power brick audibly noisy

            Originally posted by jayjr1105 View Post
            ... How can I tell if it's a 2 transistor self-oscillating design?
            A quick clue would be if there is no PWM IC and if there is no all-in-one TO-220 switching regulator IC (e.g. Power Integrations' TinySwitch or TopSwitch ICs).

            Backing up a bit, your picture in the OP shows the adapter is a flyback design (no output inductor). On the secondary side you'll probably find a TL430 or TL431, which is connected to an optocoupler. The optocoupler could provide a feedback signal to a PWM or all-in-one, or it could drive the turn-off transistor in a two-transistor design.

            In a flyback topology, the "output transformer" is actually a coupled inductor. The primary winding serves as the inductor, and the stored energy from each "on" cycle is coupled into the secondary circuit.
            PeteS in CA

            Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
            ****************************
            To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
            ****************************

            Comment


              #7
              Re: Laptop power brick audibly noisy

              Originally posted by jayjr1105 View Post
              How can I tell if it's a 2 transistor self-oscillating design?
              Just see if there is an SMPS IC on the bottom of the PCB (specifically on the primary side.)
              *EDIT*
              I guess PeteS beat me to it.
              Last edited by momaka; 03-11-2022, 12:22 PM.

              Comment


                #8
                Re: Laptop power brick audibly noisy

                It's one of the cheaper "laptop replacement" power supplies.
                Almost the same board as one I scrounged for parts, bigger transformer, same heatsinks- just wider, and the same lack of input filtering/inrush limiting.

                The small cap for the PWM IC is suspect, no matter what the markings are (can be fake).
                Use a 22-47u 50v 105 degree, such as PW, HE, FC, FR. For the output caps, use the largest value at 25v that physically fit.
                I like FR here, large capacitance for their size & low ESR/hi ripple to handle that flyback supply.
                Looks like the caps are 680u/25v.
                Try for 1000-1500u/25v, again the largest value that fits.
                Also tie the EGC from the AC inlet to the DC side negative.
                Looks like you've got a 3-wire AC inlet with the GND unconnected!


                IIRC, the control IC works like a 384x. It's a 6 or 8 pin SMD part on the back of the PCB.
                I'm pretty sure the 8-pin version does not share the 384x pinout!

                I find the output rectifier to be a weak link in these- change it to a 100v/20A schottkey or SBR part.
                UFs or FRs have higher Vf and the heatsink gets hotter.

                This is a drop in, complete with isolated tab:
                https://www.mouser.com/ProductDetail...OZiNSM5g%3D%3D
                Get one while you can...

                re: the noise. It's likely you're hearing the PWM modulate as the iron pulses the element.
                But change the caps anyway; again, they're known to be questionable in these "replacement power" adapters.
                Is that small cap original? "Looks like" a Panasonic FC- did you change it already?
                The transformer should be OK. I see what appears to be nice layering & teflon tubing on the lead wires.
                Last edited by kaboom; 03-11-2022, 10:09 PM.
                "pokemon go... to hell!"

                EOL it...
                Originally posted by shango066
                All style and no substance.
                Originally posted by smashstuff30
                guilty,guilty,guilty,guilty!
                guilty of being cheap-made!

                Comment


                  #9
                  Re: Laptop power brick audibly noisy

                  Okay, front TO-220 shaped device is "First" 16T41 - FIR8N60F and Secondary side is also "First" branded 16M01 - MBRF20100
                  Attached Files
                  --------------------------------------------------------------
                  Ryzen 3600x
                  16GB Patriot 3600MHz
                  MSI B450 Gaming Plus
                  MSI Air Boost Vega 56
                  Acer 32" 1440P Freesync
                  Rosewill Capstone 750W
                  --------------------------------------------------------------
                  Hakko FX-888D Station
                  FX-8802 Iron
                  MG Chem .8mm 63/37 RA 2.2%

                  Comment

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