Thanks very much for the reply! How would I go about tracing it?
If I put my multimeter across 12v and GND I get no reading on ohms, but also no beep on continuity (though it does show 1.007 - not sure what units this is though).
From 5v output on the DC-DC converter to GND I get 16k ohms and no beep on continuity but 0.434 on the screen (again don't know units for that).
How might I go about tracing the short?