Arduino Pro Mini I2C Problem
The Pro Mini has a 3.3 volts regulator rated to 150mA, as you can see here https://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/Arduino-Pro-Mini-v14.pdf, it´s rated to work from 16V but by personal experience a 5V~5.1V 200mA power supply is the best option to power it without burning it, even if it burns, you can search at the internet something like 

"Desoldering led and voltage regulator on Arduino Pro Mini"

Regards