I used a drop of Kroil on a 7000 plugin knob set screw when it was frozen. That stuff never lets me down. Of course, you need to use it before you strip the screw head! And, you need to be patient - like a few drops over an 8 hour period. Be careful that you don't get the stuff on the face of a Tek instrument - it will likely take the print off. But, just about anything other than a lightly water damped cloth will take the print off a Tek instrument.
