05-21-2018, 11:16 PM
As I mentioned , the 1932 run of metal tubes from RCA included a 5W4. They must have had a reason, but it could have been as simple as having a rectifier included in the set.
The 5T4 is also a metal tube (shielded). This could have been to make it more rugged for military use.
The 5T4 is also a metal tube (shielded). This could have been to make it more rugged for military use.