John,

One method that I have used in the past to find shorts is to connect a variable lab supply with variable current limiting. If it is a 5V line, then set the voltage down to one volt no load. Set current limiting down to zero, then connect. Then turn up the current limit and watch the meter... keep the current below what the smallest trace will take for the boards you are testing...

I have actually "blown open" shorts that are hairline shorts using this method. If you turn up the current to the max that the traces can take, then you can use a thermal tracer to follow the temp of the traces... the fault path will be hotter than anything else. If your lucky, the short won't be under a component... but we are never lucky are we?

Chances are it is a stray solder ball or wire fray fragment lodged under a chip.

Good luck!

Mac

Andrew. I admire your drive to go out and make things happen! Here is an idea for you. Look into PTC thermistors. These are devices that can be used in place of fuses for some applications where high current is needed for short durations, but a prolonged passing of the same current will heat up the PTC (positive temp co-efficient) device and cause the current to be significantly reduced until the fault is removed. The nice thing is that once the fault is removed, the device cools, and the "fuse" resets ready for normal operation.

I have used these in automotive electronic applications where we had to ensure that short circuits of our solenoid drivers did not damage our electronics.

Mac