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Strange transformer behaviour

  1. Jan 11, 2016 #1
    My phone adapter makes a screeching sound when switched on, but not too loud to be audible to everybody. I know there are eddies within the transformer, but other adapters do not seem to be noisy. What is that?
  2. jcsd
  3. Jan 11, 2016 #2


    Staff: Mentor

    Just a guess. Transformers have laminated cores. Part of yours may have become delaminated.
  4. Jan 11, 2016 #3

    jim hardy

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    my guess is its high frequency switching converter is cycling on-off-on-off-on-off at audio frequency
    most likely a failed filter capacitor inside

    it will quit altogether, soon , is also my guess.
  5. Jan 11, 2016 #4


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    Staff: Mentor

    How long have you been using it? Has it always behaved like this? Does it work okay as a charger/adapter, anyway?
  6. Jan 11, 2016 #5


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    Ceramic capacitors can also act as piezo speakers.

    Does the sound change when charging rather than just plugged in? Some supplies get terrible ripple when under very low or very high load.

  7. Jan 11, 2016 #6


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    This is the best response and one which I totally agree
    I have often found with failing SMPS ( Switch mode PSU's ) that as the regulation fails that the switching few drops to where it becomes quite audible

    IF you have very good electronics repair skills, these PSU's are often repairable
    IF you don't, buy a replacement, as we don't want to see you name in the obituaries

  8. Jan 11, 2016 #7


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    Can you be more specific about what is occurring and the history of the adapter?

    Is it screeching AS it is turned on, or starts when turned on and is continuous?
    If you plug it in without the phone, does it screech? If you then connect the phone, does it screech?
    Is it an OEM charger, or a knockoff?

    Actually, it probably does not matter. There is probably nothing you can do other to wait for it to fail.
    If it is a behavior that just started I'd get a new one (actually, I'd replace it anyway). I ALWAYS use OEM chargers. I don't trust the knockoffs with my device. Why try to save $20 on a charger for a 3 or 4 hundred dollar phone or pad.
  9. Jan 12, 2016 #8
    It seems to be some kind of leakage issue. It is quiet when it is engaged with the device, emits noise otherwise only. In that case, it sustains for around 20 seconds after switching off, increasing the pitch gradually and disappearing in a pattern that sounds like an open pipe is forcefully closed.
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