My laptop charger is a 110-220V AC to 18.5V DC. Of late, or maybe I just heard it now, it makes a beeping noise. The noise is very very low. I have to put my ear to it to hear it.
The charger works just fine, and the proof is that I am posting this question while using the laptop on pure AC.
I did my research on the internet and people say that this noise comes and their laptop stops working and the charger won't charge. My initial guess is that it is the step-down transformer inside that maybe the cause. I use the laptop for light use.

  • Is this beeping harmful?
  • What could cause the beeping?
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      \$\begingroup\$ Is the beeping on a regular interval? Would you say it might be more of a hum or a whine? \$\endgroup\$ – JYelton Dec 13 '12 at 5:59
    • \$\begingroup\$ @JYelton sounds like a hum. \$\endgroup\$ – Fasih Khatib Dec 13 '12 at 6:08
    • \$\begingroup\$ Battery on my computer is dead, and my charger makes the same noise. \$\endgroup\$ – geometrikal Mar 28 '13 at 1:47
    • \$\begingroup\$ The aliens inside are trying to call home. \$\endgroup\$ – Olin Lathrop Mar 28 '13 at 11:58
    • \$\begingroup\$ A closely related question electronics.stackexchange.com/q/14256/3552 \$\endgroup\$ – sharptooth Oct 16 '13 at 8:45

    Some switching/regulated power supplies seem to have a hum or a whine moreso than others. (I've a Dell laptop supply that hums.)

    You should try putting different loads on it. When the laptop is on, backlight at full, charging the battery, etc, the power supply will be under more load than when the laptop is powered off and the battery is full (or not present). Under the light load, the supply may hum more loudly or not at all.

    My experience has been that if the power supply hums or makes noise when under load, it's probably an indication of impending failure. If it hums when under light or no load, it may simply be that it's making the noise as the switching circuit engages less often. (The Dell supply I mentioned hums under light/no load, and has been fine for years.)

    A switching power supply essentially turns on and off at a high speed, and it is this cycling that can cause an audible sound.

    Try the following:

    • Try a different wall socket. There might be a problem with mains power causing it.
    • Measure the output using a voltmeter to see if it's within tolerance of the stated specifications.

    If it's a high-pitched whine or hum, it might be just fine. If it's more of a hiss or sparking sound, you might have bad components that are arcing internally, etc.

    Most power supplies like this are very difficult to open up to inspect; not recommended unless you know what you're doing and don't mind voiding any warranty. It's probably best and safest to procure a replacement supply before doing any damage to yourself or your computer.

    A related question: What component of my phone charger produces chirps and how does it do that?

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    • \$\begingroup\$ Well, I have a battery inside that doesn;t charge so should I throw it out? status: plugged in, not charging \$\endgroup\$ – Fasih Khatib Dec 13 '12 at 6:26
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      \$\begingroup\$ If you've got a known faulty battery, take it to a place that will recycle it. No sense in having it add weight to the computer and possibly causing weird things to happen with the charging circuit and/or PSU. \$\endgroup\$ – JYelton Dec 13 '12 at 6:28

    I worked at a computer helpdesk for awhile and ran across this once (I was eventually moved to networking). I remarked to my boss that I didn't think laptop chargers had beepers/buzzers in them, to which he replied they didn't, that the noise was coming from a blown capacitor arcing within the power supply.

    So based on this my answer is: The beeping is indicative of a dying laptop charger, and the noise could be caused by a blown capacitor. Basically the laptop charger is broken and needs to be replaced ASAP or you are not going to have a charger for your laptop

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      \$\begingroup\$ Second hand anecdotal evidence is not evidence or proof. There are many things that could cause the noise, but arcing is way down on the list of likely causes. -1 \$\endgroup\$ – user3624 Dec 13 '12 at 13:58
    • \$\begingroup\$ I did, technically, answer his question. I can't prove anything without seeing the charger anyways, nor could you. \$\endgroup\$ – Ramrod Dec 13 '12 at 16:19

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