Intel CMPC2010, E11IS2 Rev:C : high-pitched noise, battery not charging

[rattlesnake]

Hello people,

I'm trying to troubleshoot this laptop, I think there is some kind of short-circuit but as I'm still learning, I need some help.

As soon as the AC adaptor is plugged into the computer (with the computer still off), the main board starts emitting a high pitch noise. It's a bit like the sounds of an analog dial-up modem, but very high-pitched. I don't know how to describe it.

Nevertheless the computer can be turned on and works, but the battery isn't charging, even if the system reports it is charging (the charge is fixed at 9%).
If the battery is removed the sound remains, and the computer still works.
If the AC adaptor is unplugged from the computer, the sound immediately stops.

I checked the AC adaptor and it is providing the correct voltage (19v). I even tried with a different AC adaptor, and with a different (new) battery. No changes.

I don't know what I should check next.
Where should I start? What is the most common cause of this kind of noise?

More information:

Intel Classmate PC
E11IS2 7GE11000-C0 REV C

I attached the schematics
Here's also the manual

Here are some pictures of the main board that I took:

[caspian]

Re: Intel CMPC2010, E11IS2 Rev:C : high-pitched noise, battery not charging

Disassemble the laptop and listen carefully which component makes the noise. If you are not sure, at least you can find the limited area on the mainboard which the noise comes from. then, take a photo of that area.