Pete Higgins measured the RCA preamp voltages and current when he did his excellent reviews of the preamp.
http://forum.tvfool.com/showthread.php?p=49017
http://www.highdefforum.com/local-hd...amplifier.html
It is a little more difficult to measure the voltage under load, because you need access to the center conductor when the preamp is connected. This is one way to do it:
Method #2 is easier if you have a T-Adapter:
Measuring the current:
