hi all, i accidently broke my screen on my macbook (13" mid-2010. yosemite 10.10.2) so i bought a Mini DP to VGA adaptor o connect it to a monitor but the monitor wont say on for longer than 10 seconds, please can someone let me know how i can get it to stay on permanently? (not in clamshell mode though becuase i still need to use the trackpad) thanks!