[462ron]

    Many of these variacs are a variable auto transformer, not isolated from the mains. I’ve been using an RCA Isotap WP-27A for many years. It is not continuously variable but instead, you can vary the out put voltage in 5V steps from 25V to 150V. One big advantage is that in addition to adjustable output voltage it is also an isolation transformer, 2in 1. Works great but sometimes might take awhile to find one!

Ron