At 11:41 7/11/2002 -0500, Peter Petrakis sent this up the stick:a isolation transformer available(that huge coil thingee that lets you dial up/down the voltage and keeps yousafe).They are Variacs - not isolation transformers. One leg of the primary coil is connected to the secondary. In a fault situation there is no protection from the mains.
Worse, with a linear supply a Variac is your friend, but not necessarily with a switching mode supply. Any measurements you make at less than nominal input voltage are suspect, and you may not get some rails to come up until a certain threshold is reached. I can't speak for every chip on your board, but some don't like it when they get only the negative rail (supply) etc. Personally, without enough knowledge to render it unnecessary, I wouldn't recommend this approach, but that's just my opinion. (I'm not an electrical engineer, but I played one in a past life.)
Cheers, Phil Mendelsohn