As someone who has a collection of tube radios, I found this article interesting for a number of reasons. The author has a huge collection of tube amplifiers, and was looking for a way to resurrect them. He bought a device called a variac, which is basically just a power transformer with adjustable input. In the article he explains how he used a variac to slowly bring the capacitors inside old tube amps back to life by slowly increasing the voltage applied; this sounds like another interesting project.