[Radioroslyn]

Hi Dave
Double check the code # on the chassis tag to be sure you have the proper schematic. It will read code 121 or 122 ect... Either will work but the 5Z3 is rated at higher output current. And it consumes more filament current (3amps/ the 80 is 2amps). Generally the 80 or 5Y3 is used on sets with smaller audio output stages, the bigger sets and consoles w/ larger output tubes used the 5Z3 or 5U4.
Terry