Solidoodle 4 voltage requirements
I have not used or seen a solidoodle 4, but as found on the internet, the controller board used in the printer is a version of the Sanguinololu, and the reprap wiki says that


  The board is designed to be flexible in its power source, working with
  a 12V/5V ATX power supply or any 7V-35V power source via the on-board
  voltage regulator.


if you're using a board not older than V0.7 http://reprap.org/wiki/Sanguinololu

However, I have also found images that show the Solidoodle with this board:
http://www.reprap.org/wiki/SAV_MKI
which can be used with 11-15V. This however might be for older versions of the printer.

There are some things to keep in mind: if there is no voltage regulator on the board, make sure that all parts can take the voltage without overheating at some points.