I repaired my GT300w. The microphone was soldered incorrectly. This plus the board coincides with the plus microphone! I soldered a microphone in reverse and the problem was solved.
New features of GT300W - http://www.foxoffer.com/blog/2013/06/26 ... of-gt300w/
The new firmware come with three new features:
White Balance
Plate Stamp
Image Rotation