This base probably originated in the late 1940's or early 1950's. The designation B4A has been taken from its use on the data-sheet for CV398 and an STC catalogue.
The RCA data-sheet for the 715C numbers the pins clockwise from the notch, the CV register numbers the pins as shown above. We have adopted the UK numbering.
The ceramic B4A base with bar to fit into the notch and locking lever. od 82mm, id 46mm.
| 