Geeetech

Have a look at these they seem to be having the same problem (http://forums.reprap.org/read.php?158,130702)
Hope it's not to technical for you but it will give you some insight or something to work on

!. What is the expected amperage for the heatbed ?
2. What is the expected amperage for the hotend ?
3. also for the motors,fans etc.
when I get my new control board the first thing I'm going to do is check amperage on each individual
item and total them up !

The Mk2 heat bed look here http://reprap.org/wiki/PCB_Heatbed#About information on 12v and 24v
and general power usage http://forums.reprap.org/read.php?292,294743