HI there.I need info for 7591, 6550, 6BQ5 tubes for my jackson 648 tube tester. After reading the the info that the 648A and the 648R gave the same readings on a 6C4 tube that my 648 gave , I was wondering if the 648A and R models had these readings on their roll charts.
Roger

: HI there.I need info for my jackson 648R tube tester. I need an update specification setup sheet to test newer tubes, such as 300A, 205, 274, etc. I was wondering if there is an supplementary data sheet for the 648R.
KEN