Problem with power in Arduino Mega 2560 R3

Hello everybody.

First of all, congratulations for this huge support forum. I've been searching at least 3 days, but I didn't find the solution.

Recently, I've bought a new Arduino Mega 2560 R3 and a Sensor Shield for a robotic project. I need control 7 servos with the PWM's ports, so Mega is perfect. The problem is, there are too many servos and the USB current (0.5A) is not enough, so as far I know, an external power supply is required.

I've tried to use a power supply of 12 VDC and when I plugged it into de VIN port, the voltage is falling down to 2.5V. I don't know what's wrong. Using a voltimeter, there are 2.5V instead of 5V or 3.3V (in their respective pins).

I try to use severals power supplies but nothing change. Otherwise, I have an old Arduino Duemilanove and it's works properly, so I thought the problem is in the voltage regulator (AMS1117). I obtained this measures:

AMS117 Mega 2560 Duemilanove
Pin 1 (GND) GND GND
Pin 2 (Vout) 2.31 5
Pin 3 (Vin) 10.5 10.5

Looking this table, probably the regulator is burned, but I'm not so sure. (Actually, I wouldn't like buy another controller). So, anyone could help me, please? Thank you for your support!

Please show your schematic first.

rafalp:
Please show your schematic first.

Sorry, I attached the schematic of AMS1117 (I suppose)

http://www.advanced-monolithic.com/pdf/ds1117.pdf

I mean whole schematic of your equip.
Maybe you overloaded atmega with too much current - atmega working correctly now?

Now voltage requlator is hot or cold?
If you use 12V power supply,why its only 10.5V IN?

rafalp:
I mean whole schematic of your equip.
Maybe you overloaded atmega with too much current - atmega working correctly now?

Sorry! This problem appeared with no servos connected, the board is empty. When I use the Arduino's with USB adapter, it works correctly. So, maybe the regulator is burned, but I just want to know if it's normal, or it's a known issue (and how to fix it!).

rafalp:
Now voltage requlator is hot or cold?
If you use 12V power supply,why its only 10.5V IN?

The voltage is cold, and the led's lights bright too low with external supply. I don't know why the VIN in the regulator and in the VIN pin (near GND, 3V3, 5V... pins) is only 10.5V instead of 12V, I suppose part of the voltage is for any internal component. I advise it happens in both of Arduino's cards.

Thanks you!