My Inspiron 5150 is less than a year old, today it has developed a whistle noise (around 10Khz) when the psu is connected. The battery is charged and all else is good display etc. The noise comes where the DC connector fit's into the pwr socket of the laptop. When the pwr supply connector is removed the noise stops. It's weird because this noise starts after about 15 seconds of being connected to the pwr supply.

Any help would be much appreciated

Any clues???