I installed a new main circuit board in my phantom after discovering some broken solders that weren't repairable after a crash. Now when I fly, I get the normal green pattern for RTF w/GPS but then I get three fast red blinks after three slow green blinks.

This happens throughout the power cycle (100%-15%)  I currently only get about 14 minutes of flight with brand new fully charged batteries

Are you close to the NO-FLY zone? the LED indicator status is like the Phantom is flying on restricted area. Have you tried different location?

you're right I must have been just inside a "C" zone. 8km is further than i thought. the first time i flew it with the new board i actually got the "start up lights" (red yellow green) after taking off and flying with GPS for about 5 minutes. but i haven't been able to replicate it since.

Keep away from the restricted area, and enjoy your flight.