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buzzing transformer

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  • buzzing transformer

    i have a small (1-2 pounds) transformer. it puts out around 6v. its annoyingly noisy, with and without load. sometimes the frequency changes spontaniously. why is that, can it be fixed and how?

  • #2
    I posted a fix for this on PM some time ago. It doesn't work all the time but my experience proves it works most of the time.

    Clean the laminations and blow the dust off then drip liquid (not gell) super glue on the laminations and let it dry. Stops the buzzing most of the time.



    • #3
      Yep, typically a loose lamination in the core. So it ends up buzzing like a reed on a wind instrument. If the gap is reachable on the surface using thin CA or even thinned down varnish or shellac or pretty well any sort of thin runny stuff that hardens up will work. If it's an internal delamination or you can't reach an opening due to the windings bobbin being in the way then not much you can do other than buy another transformer.

      If you're REALLY desperate you COULD try simply dipping the whole transformer into a can of varnish, let it sit and soak for a minute then pull it out, drain and let dry for a few days. That's provided it's an open style construction. If it's inside a working unit or on a board then you could still dip it like this if that part of the board will fit into the varnish. Or you could try slathering on a lot of it with a brush then drain and keep your fingers crossed. Of course this means leaving it open and not powered up so it can dry for a few days.
      Chilliwack BC, Canada


      • #4
        I'm for the dunking in varnish idea. Every time I mess with CA, I end up with fingers stuck together.
        “I know lots of people who are educated far beyond their intelligence”

        Lewis Grizzard


        • #5
          That is why you often see a weld bead ran across the lamination's, particularly on higher Va versions.


          • #6
            The laminations should be insulated to reduce eddy currents, which can result in excess current draw and heating. So welding the laminations can present a problem, although perhaps not significantly..



            Paul , P S Technology, Inc. and MrTibbs
            USA Maryland 21030


            • #7
              The frequency can't change assuming it's powered from the wall socket 120 volts. The power grid is very stable so I suspect your measuring equipment if your freq is changing.

              Are the coils loose on the iron core? That'll make it rattle like mad. If so make some wood wedges and tap them in between the coil and the core to tighten it up. Then do the dip procedure. Subemerge it and if possible put a vacuum on the container to get the bubbles out. Let it cure or bake it out in wifey's oven. You should be good to go.


              • #8
                Originally posted by I make chips View Post
                Let it cure or bake it out in wifey's oven. You should be good to go.
                The man lives dangerously...........Based on life experiences, yeah, you should be good to go....down to the appliance store and buy wifey a new oven


                • #9
                  The sound emitted by a loose lamination can change depending on what other loads are coming on. You might hear a vacuum cleaner for instance, or a skil saw. It depends on how sensitive a loose lamination becomes. And it's not just the laminations that can be loose- it can be turns of wire too.

                  Quite often it's one of the outer laminations that would be loose, if there isn't a folded steel bracket to restrain it, or something similar. CA works pretty well usually- or what I do in some cases is mix up some finishing epoxy (because it's thin enough to wick into gaps) and apply that.

                  So far we're assuming a 60 hz transformer- you could be talking about a ferrite type which operates at a high frequency. In that case you can try to find the gap and wick something into it. The gap could be in the normal place, or it could be a crack in the ferrite. All kinds of noises can come from that. In any case I would be far more inclined to use a thin epoxy instead of CA or varnish, as it will cure fully- not needing heat or 'drying time'. Assuming you mix it right of course-

                  Ferrite is a funny thing- I have read that you DON'T want to epoxy the core because it will change the magnetorestrictive properties. But the only problem I've had is that once epoxied, you can't take it apart.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                  • #10
                    If you are going to use epoxy I think the only thing to avoid is one that is filled with iron or steel particles. Most epoxies will be OK, but not ideal.

                    They do make varnish/coatings for this. If the loose laminations are not on the surface, then do look for one that is thin enough to penetrate down to the core.


                    Paul A.
                    SE Texas

                    And if you look REAL close at an analog signal,
                    You will find that it has discrete steps.


                    • #11
                      Originally posted by tom_d View Post
                      The man lives dangerously...........Based on life experiences, yeah, you should be good to go....down to the appliance store and buy wifey a new oven
                      Might I add that baking varnish is rather benign. Put it on some aluminum foil to catch the drips, not one of wifey's cookie sheets.
                      *I bake things out when she's gone. I'm no ordinary dummy.


                      • #12
                        A thin or thinned varnish like material, CA will work, but not the best. If you have access to a vacuum pump, use it to help the varnish penetrate deeply into the transformer. The best way is to submerge the transformer in the varnish and apply vacuum for 30 minutes or so. Then rapidly release the vacuum. Let it rest in the varnish for 5 minutes and then repeat. Do this several times to remove the maximum air from the laminations. when done remove from varnish and let drip to remove excess. last, cure the varnish as stated on the instructions. Often low heat for many hours works best. Enjoy the silence!!!!!

                        Happily working on my second million Gave up on the first


                        • #13
                          Well, i took the cover off and the device was whisper quiet. i toutched the cover to the tranformer and it resonated badly. what a stupid design. so i put the cover back on and its a bit louder than without but not noisier than any other transformer. problem solved.

                          on second thought it might have been the the tongue on the fuse vibrating, it seemed not to make proper contact so a bent it a bit more.

                          i use this to trim grass with a ex-cordless shear.

                          Attached Files


                          • #14
                            It is pretty common for a cheap transformer to make a steel cover vibrate. You can often see this with a microwave oven, which often will cause a "bang" when started up, as power is applied to the extremely cheap transformer. The initial current surge creates a magnetic field that pulls the cover. Some will continue to buzz during use.

                            Microwave ovens are not the only culprit. Cheap transformers, no matter what they are in, "leak" magnetic field, and usually the transformer is very close to the steel case of the unit. The solution is to put a rubber pad between the transformer and the cover, to damp down the motion of the cover. (or just put something heavy on top of it)
                            2801 3147 6749 8779 4900 4900 4900

                            Keep eye on ball.
                            Hashim Khan

                            It's just a box of rain, I don't know who put it there.


                            • #15
                              why not plastic covers?