The 220 (aka 20) is a power triode. It is used as an audio amplifier in early battery type radios from the 1920’s. 1 Cunningham CX-220 aka 20 Vacuum Tube. Hickok TV-7D/U test reads 22. This tube is from early 1930’s USA production.
The 220 (aka 20) is a power triode. It is used as an audio amplifier in early battery type radios from the 1920’s. 1 Cunningham CX-220 aka 20 Vacuum Tube. Hickok TV-7D/U test reads 22. This tube is from early 1930’s USA production.