Mike jigged a 21FBP22 CRT to my Westinghouse H840CK15 chassis during restoration. This was to test circuits and verify the restored chassis operation prior to installation of the 15GP22 to help avoid possible mishaps. A few photos of the Westy performance on the 21FBP22. The images are a bit blurry because the voltage values are from a chassis designed for the 15GP22.
