On Thu, 14 Jul 2016 18:45:05 -0000 (UTC), Cursitor Doom
wrote:

When connected to an external bench power supply at 12V., the board draws
9.3mA. The bench PSU doesn't have any issues powering this board.

When connected to PSU that uses the LM317, however, it draws 3mA and the
voltage across it drops to around 6V.

Average or peak currents? Better yet, put a resistor in series and
look at the current waveform on a differential scope (using 2 probes).
I would not be surprised to see the LM317 oscillating at some fairly
high frequency. If so, you need a BFC (big fat capacitor).

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558