dhenry:
For powering up those unit, the typical approach is to put a light bulb in serial. If the light bulb glows, you have a problem.
I was just about to suggest this. It is called a dim bulb device and I use it all the time for powering up antique and questionable electronics. You can start with a low bulb and slowly go higher.
A small glow should be ok. Lighting up brightly indicates a short.