6A7 tube substitutes?

[dieseljeep]

Originally Posted by 7"estatdef

Better order one. None of your others will fit into the socket. 6a7 /2a7 are odd balls. Electrically they are the same as a 6a8 but they are octals.
GL
Terry

IIRC, the 6A7 was the first pentagrid converter tube and not really an oddball tube. They were being used from around late 1934 to the late 30's.
Some firms adopted the octal based tubes earlier. Many still used the UX bases much later, Philco especially.
The pentagrid tube replaced the use of the separate oscillator and mixer tube or the autodyne converter setup.