Tube plate voltages can get scary.
I've never gotten into collecting Radios in any serious way, but do have a few. After stumbling across a few Zeniths, I've developed somewhat of an interest in them(although not serious, as they get pricey and take up a lot of space). I appreciate quality, and the first Zenith chassis I pulled out made my jaw drop compared to its contemporary Philcos and the like.
In any case, one of my "prizes" is a late 1950s Trans-Oceanic. Like all of the tube Trans-Oceanics, it's designed to run on either battery power or line power. Unfortunately, mine is missing an impossible-to-find tube(or probably more correctly, a very expensive tube) that is actually just a big ballast resistor in the rectifier circuit. Running the radio on battery power bypasses that part of the circuitry.
Of course, radio batteries are no longer made, but there are ways to improvise. The Trans-Oceanic needs 9V for the filaments, and 90V for the plates. So, with that in mind, I built my own battery pack by using 10 9V batteries in series(just snapped + to -) for the plates, and 6 D cell batteries in series for the filaments. It works perfectly, and turns on instantly(there's no perceptible warm-up time). Still, though, 90V DC actually scares me a fair bit more than 120V AC.