t420 coil whine, anybody?

[e_mati]

Hello
I have a problem with my thinkpad t420 - it's this irritating coil whine. From my observation it's the most noticable when my thinkpad is in standby mode and running on battery only. The source is i think somewhere in top right corner, around usb ports. I already been with this problem in service 2 times, at first they did nothing but second time i got new motherboard. Unfortunately, this didn't solve my problem, coil whine is still present and i have no idea what to do with this. I have no such problems with my x200, x60 or x300 so i came here to ask am i alone?
Or maybe this is common for some t420 series?
What should i do with this?
My warranty expires in next month i think