This charger is very convenient because it is equipped with a transformer suitable for many computers in the mid range pc. Only when the computer is not under voltage, the charger him the rest and passive operation makes it create a fairly loud noise, close to a ultrasound. This is quite annoying and disrupts fast enough, we must disconnect the power supply of the extension to stop the noise.
After, it's not a high-quality charger, like all electronic devices of this kind, they have their default ..