The 5666 / 5666A / F5666 / F5666A / ML5666 triode tube is one of the many tube types that Kennetron rebuilds. Contact Kennetron if you need a rebuilt 5666 / 5666A / F5666 / F5666A / ML5666 tube or have a 5666 / 5666A / F5666 / F5666A / ML5666 tube that needs to be rebuilt.