I built a board that combines a number of sensors, an ATmega2560 and a TPS62125. The board worked, I was able to measure 3.3V coming out of the buck regulator, and was able to program the ATtmega via ISP. Then, trying to fix another issue, I applied flux to all the pins of the ATmega and reheated them all with an iron, trying to clean them up a bit (it's a TQFP package, and I had some bridging that I originally cleaned up with a wick, but it left behind some crap).
After that, it stopped working. I can only measure about 12mV on the power rail now, but the circuit is still drawing 16mA @ 12.3V from the battery (which is about where it was before). The cause and effect seems pretty clear - I either created a short with the iron that I can't see now, or I fried the chip and there's an internal short. That said, is there anything else I can look at to verify this? I'd have thought that a short to ground would at the very least draw more power. The buck regulator is rated for 300mA so I'd expect a short to ground to draw the full watt or so (300 * 3.3V), but it's only drawing about 200mW.
I checked that the enable pin is high on the regulator (it's pulled up to the battery). Anything else I can look at?