The original 0Z4 and the one I build has no heater so 6 or 12 volt is no problem ,it's a full wave rectifier, takes in AC voltage gives out DC voltage,so polarity is no problem. It is also a direct replacement for the 6X5, witch did have the six volt "A" and is not needed, 6X5 is found in some car radios and house radios of the late 1930's and in to the 40's. Last year I restored a 1940 Zenith console radio, I replaced the 6X5 with one of my 0Z4 replacement ,
I build these using the original tube can so it looks 100% original , by the way I have several good 0Z4 inners, you could rebuild your own 0Z4 or make some kind of project ,they glow purple with AC on them , for the inners I don't use I'd sell them 5 for $1
