Build a Short Circuit Sniffing Power Supply.
A handy piece of test equipment to have on your work bench is a DIY Short Circuit Sniffing Power Supply.
A small prototyping PCB, a few common electronic components and a plastic case gives a compact test unit.
The PNP transistor needs to have a gain of ~200 while the NPN needs to be ~100.
Q1 has a heat sink attached.
External wires connected to this power supply should be 18 AWG.
See discussion at this link for using this power supply.
http://forum.arduino.cc/index.php?topic=601183.0
Two versions of the power supply are offered in the attached PDF.
Root_1.pdf (11.7 KB)