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I have 12 V power supply (one of these you can find with most laptops and other hardware) with current rating of maybe 2A. When it is loaded, it works and it is silent, but when the load draws small current (in power-saving mode) or the load is disconnected, it starts making a clicking noise, approximately at 1.5 Hz. As far as I know, the sound could be produced by some inductor.

Is it safe to use the supply? The supply was already used previously and I do not know whether it made this sound when it was new.

jiwopene
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  • Do you have a schematic of the power supply (this site is about design of circuits). Maybe there is a burnt out resistor that forms a minimal loading circuit inside the power supply? It sounds to me like this may be a problem and that the internal crowbar circuit is repeatedly tripping. I'm giving you this info in comments because it's off-topic to ask for opinions. Get a new one is also my opinion. – Andy aka Sep 24 '22 at 18:58
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    Fairly normal. Search for pulse skipping. It’s a common method to save losses at light load. – winny Sep 24 '22 at 19:06
  • I have a power supply that I use all the time at work that makes a ticking noise while powered on. It came with a label on it saying "Ticking sound in operation is normal". It's an HP 6525A, a low-current high voltage supply from the era when "fully transistorized" was a selling point. It uses the biggest flyback transformer I've ever seen and runs at an extremely low frequency, even for a flyback converter. When heavily loaded, it runs at an audible frequency of a few kHz, and when lightly loaded, it runs at a frequency proportional to load, as low as about 2 Hz. – Hearth Sep 24 '22 at 19:29
  • That doesn't really answer your question, but the point is: power supplies making ticking noises is normal in some cases. There aren't really any failure modes that need to be worried about that would cause a ticking noise either. Might just be a sign that some glue in the supply meant to prevent that noise has come loose. (though in that case, something may eventually be damaged by vibration...) – Hearth Sep 24 '22 at 19:30

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Many power supplies do that, either the inductors/transformer vibrate due to magnetostriction, or the ceramic caps vibrate due to voltage ripple. It emits the noise all the time, even under load, but then it's ultrasonic so it's not audible for humans. It becomes audible when the power supply goes into cycles of sleep/wake-up to save power when it is unloaded, and these cycles occur at an audible frequency.

So it's probably normal, even though it's annoying.

bobflux
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  • Or at a sub-audible frequency, which seems to be the case here. They're getting ticking sounds, not a continuous tone. – Hearth Sep 24 '22 at 19:06
  • Even if the repetition rate is at 1Hz, the clicks contain a wide range of frequencies which will make them quite annoying – bobflux Sep 24 '22 at 19:18
  • Of course. But the cycling in and out of sleep mode is at a lower frequency. – Hearth Sep 24 '22 at 19:19
  • It might also not be sleep mode, but that would be very unusual. I have a power supply at work (mentioned it--and then rambled about it for probably too long, oops--in a comment on the question) from the 60s that actually just runs a flyback converter (all implemented in discrete BJTs and diodes, from control to switch) under hysteretic control, so at light loads the converter actually just runs at 2 Hz. – Hearth Sep 24 '22 at 19:32