My original tumblr post was here. I reblogged this image from Cover Browser. It is the October 1942 cover of Thrilling Wonder Stories. The ISFDB entry for the issue is here, along with a slightly brighter version of the same cover:
The cover art is by Earle Bergey.
Like the trailers that are better than the movie, I think this picture is probably better than the story. Green, grinning ape-like imps, spark gap thermionic emission of electrons across a 1/2-naked girl, and a hero in a 3-pc suit. My imagination is revved up!!
My reading of the underlying pulp stories (when I can find them) makes me highly confident that you are correct.