Hello, I have an Acer a5520 laptop with a 19V 3.42A AC adapter. When the battery is charging or when the processor exceeds 1.5GHz there is a data-burst sounding squeal which emanates from the AC adapter. It's like "pfffftttt pffffffttftftft ptftftftft". It's more annoying than the anti-loitering mosquito tone. I am 31 and can clearly hear this sound.
Since it seems to be related to load on the adapter (charging or increased processor speed) I speculate that the adapter is under-sized for the load. First, has anyone had a similar problem and what did you do to resolve it and second is there an increasing trend where laptop adapters are undersized? This thing is as long as one and a half credit cards lined end to end and as wide as 1/3 of a credit card. The adapter gets warm or at times hot and I fear dampening it with some foam would cause it to overheat.
There are two fairly common sources for that kind of squeal you're hearing from that switching supply. Less common is an electrolytic capacitor degrading and causing the electrodes within to move around. The more common is magnetostriction in an inductive component that has been inadequately potted. Those like to move around in normal operation -- it's only the potting that damps the sound. If the potting has degraded and/or was inadequately applied (like they didn't pull a high enough vacuum on it to pull the compound into all the open spaces) the magnetic core itself can emit quite a noise. Same for windings moving around. This doesn't usually mean that the supply is destined for failure any time soon, but the annoyance factor can be appreciable as you've discovered.
All that said, it could be some other cause too. Keep an eye on the temperature of the adapter. "Warm" isn't unusual. "Too hot to touch comfortably" is.
