Thanks to all thow responded - and for the excellent descriptions of how it all works. After experiementing with a load, I decided that it looked good enough to try at full power, and did so with no problems - the transformer buzzes more loudly than a standard one, however I am told that this is normal for a C.V. unit. Playing with the Variac, I confirmed that the power supply truly does provide superior line regulation - from 90v to 120v, the output of the supply is pretty constant at about 9v, and barely changes. It is also much more stable with changes in the load than a standard supply. Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html