The TZ-20 is a zero bias triode with a mu of 62 and a maximum frequency of 60 MHz made by Taylor Tubes. Later tubes as seen in the second example had a plate insulator and brown base.
Length = 6.50" Diameter = 2.25"
Max voltage = 750
Max current = 75 ma
Fil voltage = 7.5
Fil current = 1.75 amps GOTO INDEX